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screen printing => Screen Making => Topic started by: Frog on May 20, 2011, 03:29:08 PM
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I have one for you that constantly springs up. I have always learned that correct exposure time is correct exposure time regardless of bold shapes, fine detail, or halftone dots.
Could you address this?
Also, does the ability of photopolymer emulsions to benefit from re-exposure enter into this picture?
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Yes Frog, I've always had issues with getting halftones to wash out when exposing fully. We usually have to back off of the exposure time by a light unit or 2 with really fine halftones. I'm sure our film density has a lot to do with this, our emulsion being PP and not dual cure, and maybe other factors I'm not aware of.
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If you over-expose you will get more under-cutting, burn-through and light scatter. These affect small elements disproportionately (because two are edge effects) which means halftones & fine lines. Whatever you do you will get scatter from the film, from the mesh, from the exposure booth etc.
So you expose enough to wash the details out, then you can post-expose to fully cure the screen that's left.
From the emulsion's point of view, when it's exposed, it isn't going to get more exposed no matter how much light you give it.
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Yes Frog, I've always had issues with getting halftones to wash out when exposing fully. We usually have to back off of the exposure time by a light unit or 2 with really fine halftones. I'm sure our film density has a lot to do with this, our emulsion being PP and not dual cure, and maybe other factors I'm not aware of.
Choosing a good match of dot to mesh helps, as does pressure washer, and art/positive adjustment when needed.
I would rather have a strong, fully exposed screen capable of long runs and quick easy reclaim than to underexpose.
Underexposure is the MAIN problem for new people in this industry, I find many of the suppliers promoting underexposure and it directly harms many of the new people in their early quest for efficient procedures an quality printing.
Have you noticed how many out there selling, hawking, and pushing products are ignorant of correct procedures, exposure, coating, positives, and art production? (Or lying for whatever reason?)
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Have you noticed how many out there selling, hawking, and pushing products are ignorant of correct procedures, exposure, coating, positives, and art production? (Or lying for whatever reason?)
Phfft. Yea, Thats why I dropped using one of he MAJOR suppliers in our area/actually nationwide I guess...and went with using Chris Colton and family. They were all intelligent and honest people. They knew what they were selling and also would tell you what was best after you've chosen to stick with the cheapest. They would lay the truth out for you and let you make the division. Many just tell you what they sell and push that product....and they don't know for sure if it's good or they lie to you. They just push it because it's what the company is selling that they rep. 14 years ago, one company tried to push an oyo on us (VERY hard) when it was clear we were looking for a true wet film image setter. It's just what they sold. They pushed so hard and lied to me that I decided not to use them at all for all of the other products that we were getting from them. We had to stick with them for some things and used them on emergency's of course, since they were in town.
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Underexposure is the MAIN problem for new people in this industry, I find many of the suppliers promoting underexposure and it directly harms many of the new people in their early quest for efficient procedures an quality printing.
New people don't understand the value of a quality exposure system, but think that an inexpensive system will do as well. The same is true for a vacuum frame verses foam compression. And of course a timer is just as good as a light integrator.
Cheap units tend to have long exposure times, so it takes 10 minutes just to produce the underexposed screen with soft edges. Washout is inconsistent.
The need for especially dark film is a symptom of an out of control exposure process.
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Cheap units tend to have long exposure times, so it takes 10 minutes just to produce the underexposed screen with soft edges. Washout is inconsistent.
The need for especially dark film is a symptom of an out of control exposure process.
I don’t know if I would call it out of control, I can show someone how to control that - it is a situation that needs direct and specific attention.
A positive with low D-min and very high D-max is a good thing regardless of the power of the exposing unit...
We had to ban the use of amber masking film and then Ruby masking film because of burn-through with a very high power MH system (one of the big guys that would take a 5x8 foot screen and would dim the lights when punched) we had a high quality SA wet bath roll feed image-setter (24”x300’ roll feed) silver based system that had beautiful positives later and were using silver film from a camera before that and had the quality positives to make up for the ban on masking films... Amber was easy to see and crap to shoot... ruby ended up as a pale contender to silver films...
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Blasting through rubylith would be my definition of "overexposed".
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I spent years formulating masking films for Autotype.
Amber actually has the highest uv density OD 4 +, Ruby was slightly lower.
I suspect that you weren't burning through the mask in the uv, an OD of 4 stops 99.99% of light at that wavelength, but that your bulb was putting out some visible wavelengths to which your screen was slightly sensitive. The Amber lets more visible light through than the Ruby.
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Douglas has a cool, interesting, one-of-a-kind story about a super powerful unknown lamp and a un-common, "high quality SA wet bath roll feed image-setter (24”x300’ roll feed) silver based system". This would be in the "Formula One" stratosphere of equipment, especially on "theshirtboard".
In Wisconsin, I knew a guy with a rocket powered car. His gas mileage was poor.
For the rest of us here on earth, 4.0-4.2 UV density masking films work very well, especially in this age of 1.6 UV density 'stock' ink jet positives where many art departments don't want to bother with increased UV density they can get from a US$500 RIP.
I've personally made more screens in the sign or flag business with masking film than most people have had hot dinners and I was the Ulano product manager that lead the program to kill AmberLITH because of poor sales. I was very sorry to see it go.
"Cheap" is usually mixed up with "Low energy". I would phrase an opacity statement differently than 'yorkie'. I encourage desire for controls, that's why I like to measure. More UV density is more control. I'm a silver film lover from the 1970's.
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Your using silver based film?
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Since I am needling my friend Douglas about his professional 'old school' 24" silver film image setter, I went on record that I miss photographic films for screen making.
"I'm a silver film lover from the 1970's", but alas most film use stopped at the turn of the century as film companies stopped making it and EPSON introduced the Photo Stylus 3000 for only US$1,100. Much less than a wet darkroom or image setter.
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Since I am needling my friend Douglas about his professional 'old school' 24" silver film image setter, I went on record that I miss photographic films for screen making.
"I'm a silver film lover from the 1970's", but alas most film use stopped at the turn of the century as film companies stopped making it and EPSON introduced the Photo Stylus 3000 for only US$1,100. Much less than a wet darkroom or image setter.
There is a film house not to far away from here. When I was starting they were producing some of my films. The Dmax and the resolution is just unbelievable! It is pitch black, as in I have this piece of plywood and it is not letting any light through! And the halftone crispness was perfect. When you look at the halftone dots from an inkjet they are lumpy. Better ones look like potatoes and the cheaper ones look like blackbarries. Imagesetter film is perfectly round, no bumps nothing, just a circle (for a round dot). I've looked into getting one, but it is just not worth it. Customer will not see the difference so it is hard to justify the price. Still . . .
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Since I am needling my friend Douglas about his professional 'old school' 24" silver film image setter, I went on record that I miss photographic films for screen making.
"I'm a silver film lover from the 1970's", but alas most film use stopped at the turn of the century as film companies stopped making it and EPSON introduced the Photo Stylus 3000 for only US$1,100. Much less than a wet darkroom or image setter.
With the price of silver the use of the old silver based films is... well, do any of us know anyone who uses them?
Speed was an issue, silver imagesetters are (or were) very fast when up against an inkjet.
Amber always sucked, sorry guys, but it always sucked, I have a few samples left over and throw them on the unit every once and a while to show someone how they suck even up against an inkjet (with the special film).
Do any of us actually want to weed film cut with an x-acto again? I have better things to do at 3 in the morning.
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My memories of silver film is a bit more tarnished. I got involved with prepress with the introduction of a linotronic 300 running postscript level 1 on a 10 mhz rip. At that time, the linotronic was considered one large step backwards in quality. pre-press was accustomed to 4.0 film density, but the first generation of helium-neon film was lucky to get 3.1 on a good day. Put a newspaper on a light table and put lino film on top of it and the newspaper could clearly be read through the film. It was a LONG uphill battle to prove that lino film was usable.
Inkjet film is an entirely different animal. With silver, all of the silver starts off on the film, then the laser determines where the silver should be removed. With inkjet, the film starts clear and ink is piled on top of it. In the case of inkjet film, there is such a thing as "too much ink".
The Middle Way is the path between the extremes of self-indulgence and self-denial.
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Since I am needling my friend Douglas about his professional 'old school' 24" silver film image setter, I went on record that I miss photographic films for screen making.
"I'm a silver film lover from the 1970's", but alas most film use stopped at the turn of the century as film companies stopped making it and EPSON introduced the Photo Stylus 3000 for only US$1,100. Much less than a wet darkroom or image setter.
You know who it was Richard one location had 12 to 16 full time artists the other had over 20 the smaller location alone had three full time “camera people” that did nothing but shoot wet acid processed silver cut sheet film (not PMT even if both locations had PMT in the early days).
When we actually transferred to using an imagesetter we gained a full time artist and could let the camera people do something more productive in the shop.
Anyone remember the horrid metal arc exposure systems, we started there and graded up to three monsters that I have no idea if stuff like that even exists now.
So now I get to bother Richard a bit...
Why don’t any of the emulsion companies ever test product with the low-power units? Does anyone there ever understand the confusion that happens with the sheets included with the product?
Why don’t more makers and suppliers push for the use of exposure calculators (including the excellent one KIWO makes)?
Why do so many suppliers encourage so many to underexpose?
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Why did Step Wedge Man and Exposure Lad constantly have to come to the rescue on the old board?
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My memories of silver film is a bit more tarnished. I got involved with prepress with the introduction of a linotronic 300 running postscript level 1 on a 10 mhz rip. At that time, the linotronic was considered one large step backwards in quality. pre-press was accustomed to 4.0 film density, but the first generation of helium-neon film was lucky to get 3.1 on a good day. Put a newspaper on a light table and put lino film on top of it and the newspaper could clearly be read through the film. It was a LONG uphill battle to prove that lino film was usable.
Inkjet film is an entirely different animal. With silver, all of the silver starts off on the film, then the laser determines where the silver should be removed. With inkjet, the film starts clear and ink is piled on top of it. In the case of inkjet film, there is such a thing as "too much ink".
The Middle Way is the path between the extremes of self-indulgence and self-denial.
I can say outside of the smell of the acid bath processors I don’t remember anything “bad” about silver films, and nothing but good to excellent for silver based film and imagesetters. The one thing I do remember was that the numbers on production output with the imagesetter to justify buying something that cost more than a few years salary of the art staffers was blown out of the water we did not even come close to how much more we were able to produce. The smaller staff alone would average between 3/4 and 1 and a 1/2 rolls of film a day, we had used cameras for so long we were not ready for the ease - of course Adobe separator was released slightly before that and that changed everything.
The film positives we gained from the imagesetters was “da bomb” I have a sample I saved and yes the dots were beautiful lines clear and sharp and the D-min and D-max were a thing of awe... at least compared to the inkjet output that at least is reasonable where folks suffering with the xerox process vellums have the worst of both worlds...
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Why did Step Wedge Man and Exposure Lad constantly have to come to the rescue on the old board?
Imagine that ::)
I often think that I end up encouraging overexposure because I see so many problems with underexposure.
I have come across printers in tears of frustration over related issues.
putting under and over exposure on a chart with pro and con (and correct in the middle) it may well be that overexposure could end up with far less “cons” and far more “pros” than underexposure.
I can tell you I have never come across problems with overexposure in the wild because I have only found underexposure and not a single case of overexposure.
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getting folks to do a step wedge test, either one step films, or manually moving opaque sheets, opens their eyes at least to what correctly exposed emulsion looks like, compared to over and under exposed.
It's just tough to get some folks to sacrifice an otherwise good, usable screen of each common mesh and emulsion combination. They would rather proceed to ruin three others screwing around insread!
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getting folks to do a step wedge test, either one step films, or manually moving opaque sheets, opens their eyes at least to what correctly exposed emulsion looks like, compared to over and under exposed.
It's just tough to get some folks to sacrifice an otherwise good, usable screen of each common mesh and emulsion combination. They would rather proceed to ruin three others screwing around insread!
So true, so sad, I do try and fix that...
I don’t talk about less-than-10% dots, because most of the time I am just trying to get new people to stop trying to get 65lpi on a 110 white mesh by underexposing QTX...
How do we get them to print halftones and deal with how they are coating 1/1 sharp and don’t understand why there are problems with the 45 deg. angle dots...
How do we get them to understand the relationship with low-power exposing units and reasonable quality positives with some dealers pushing vellum and parasites pushing pathetic “work-arrounds” and blasting users of inkjet RIPS?
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A lot of people are simply lazy, and want you to just tell them the correct exposure time for their emulsion using their 500w halogen worklight exposure unit that might be 6 inches or 6 feet from the screen, with an old t-shirt, some foam, and a concrete block piled on top for compression. We all started somewhere not very pretty, but too many can't be bothered if results aren't instantaneous and easy like they saw on YouTube.
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A step wedge test will determine correct exposure with the film supplied in the test kit. If the films you output aren't the same dmax value (more than likely less opaque) then real exposure times would be less?
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A manual step wedge test done with a typical film of yours could be more relevant.
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Speed was an issue, silver imagesetters are (or were) very fast when up against an inkjet.
Amber always sucked, sorry guys, but it always sucked, I have a few samples left over and throw them on the unit every once and a while to show someone how they suck even up against an inkjet (with the special film).
adidas/Reebok in Indy was the last place I saw two big Agfa image setters. Hardly an average art department.
Douglas, would you bring me a small clipping to the Indy Printwear Show, of the AmberLITH you have so I can measure it on my UV densitometer?
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Ya know, I had always thought that the Ruby was a better blocker, and we sacrificed that for the better visibility of cut lines through the Amber.
One thing is sure, the Ulano (and other brand) tubes make great containers for fishing rods.
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getting folks to do a step wedge test, either one step films, or manually moving opaque sheets, opens their eyes at least to what correctly exposed emulsion looks like, compared to over and under exposed.
It's just tough to get some folks to sacrifice an otherwise good, usable screen of each common mesh and emulsion combination. They would rather proceed to ruin three others screwing around insread!
Since my first feature article in Screen Printing in the late 1980's "Measuring Diazo Exposure" I have promoted using a US$10 Stouffer T-2115 transmission on every exposure to monitor stencil hardness.
No screen needs to be sacrificed. Every screen has the test scarred in the stencil. The math is easy to correct your NEXT exposure. Ready, Fire, Aim. Perfect for fluctuations in emulsion and degrading UV sources.
Properly used, a single 5" test positive should last a lifetime. I have them with me always and sell them at shows for US$10 - pretty girls get them for free. You can surprise most Nazdar reps by asking them to lookup "21step".
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A single hit of Epson 1400 yellow ink is UV opaque enough to produce screens. (cyan and magenta are UV transparent)
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getting folks to do a step wedge test, either one step films, or manually moving opaque sheets, opens their eyes at least to what correctly exposed emulsion looks like, compared to over and under exposed.
It's just tough to get some folks to sacrifice an otherwise good, usable screen of each common mesh and emulsion combination. They would rather proceed to ruin three others screwing around insread!
Since my first feature article in Screen Printing in the late 1980's "Measuring Diazo Exposure" I have promoted using a US$10 Stouffer T-2115 transmission on every exposure to monitor stencil hardness.
No screen needs to be sacrificed. Every screen has the test scarred in the stencil. The math is easy to correct your NEXT exposure. Ready, Fire, Aim. Perfect for fluctuations in emulsion and degrading UV sources.
Properly used, a single 5" test positive should last a lifetime. I have them with me always and sell them at shows for US$10 - pretty girls get them for free. You can surprise most Nazdar reps by asking them to lookup "21step".
I will tread lightly as I was forced to make an oath to not quibble with the experts whom we are so grateful to have here, but, in 1988, my photographic positives were much more likely to be closer to the same D-min and D-max of these guides than the plethora of media and opaque mediums that we have since experienced. Granted, that many of these combinations were found to be lacking, but they were in use nonetheless. Even with all of the goodies available, it is a fact of life that in this industry, many work their way up to the good stuff and the right way.
A test done with the user's actual stuff really reflects actual repeatable, verifiable results. Besides, even when the new employee misplaces the guide, you can always find a piece of cardboard.
Oh, and you can still surprise some Ulano reps, or at least distributors, asking them for the free Exposure Calculator Kit they offer.
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A single hit of Epson 1400 yellow ink is UV opaque enough to produce screens. (cyan and magenta are UV transparent)
(http://www.richardgreaves.com/images/sp/DensityCalibrationWMediaSet.jpg)
I just spent 45 minutes looking for the actual film I made with an EPSON 2200 in 2005. The yellow had terrible UV density, so I ignored it - black had the only stopping power. I will find this film or anybody can send me a small 1" patch on film for me to measure with my Transmission UV densitometer.
2732 Biddle Avenue
Wyandotte, MI 48192
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I measured the uv density of all the inks, black was the highest OD, then yellow, not very good but you could get a screen out. Cyan and magenta were indeed, pretty poor.
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Failure of the positive (positive failure), like a bad raincoat, will always encourage screen makers to under expose, because they haven't protected their image area from exposure.
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Just how good does the raincoat need to be?
(http://c.photoshelter.com/img-get/I0000JNyJkhvkoyA/t/200/I0000JNyJkhvkoyA.jpg) (http://3.bp.blogspot.com/_P3pyPRRXeYM/RovFcxDGamI/AAAAAAAAABI/T0vTmzHpryI/s320/NY+trip+and+Wayne%27s+wedding+104.JPG)
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Failure of the positive (positive failure), like a bad raincoat, will always encourage screen makers to under expose, because they haven't protected their image area from exposure.
And poor quality positives (no RIP, poor ink, laser printer vellum) are common and of course underexposure is what Richard - 98 to 99%....
So can we test this idea - lets see.
An SBQ film product (Cap film) this is basically QTX in a cap film (QT film).
The actual and full exposure was tested and used (the Cap film was to eliminate human error).
So full exposure with three positives - one with a RIP good quality film and special inks, one without a RIP and standard inks (with a good quality film same as the RIP), and one positive from a laser printer.
Mist sprayed to soften, then low pressure fan spray from a hand sprayer (not a pressure washer)
Top is laser printer, mid is no rip, and bottom is RIP and inks.
(http://i60.photobucket.com/albums/h40/douglasgrigar/SBQ_4m_MST.jpg)
Three min. hand sprayer
(http://i60.photobucket.com/albums/h40/douglasgrigar/SBQ_1m_LP.jpg)
One min. fan spray pressure washer 20 inches.
(http://i60.photobucket.com/albums/h40/douglasgrigar/SBQ_1m_LP.jpg)
Full two min. pressure washer
(http://i60.photobucket.com/albums/h40/douglasgrigar/SBQ_1m_HP.jpg)
Five min. pressure washer
(http://i60.photobucket.com/albums/h40/douglasgrigar/SBQ_2m_HP.jpg)
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(http://www.pcbsupplies.com/media/00/a20791612bd17763a1d0dc_m.jpg)
Isn't there something missing from your screen?
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([url]http://www.pcbsupplies.com/media/00/a20791612bd17763a1d0dc_m.jpg[/url])
Isn't there something missing from your screen?
No, I use an exposure calculator, I abandon the use of the 21 step scale as I found it difficult for my students to use, and often the numbers used for the 21 are underexposed when compared to the exposure calculator (numbers given not tested).
So for example on Ulano’s site...
QTX Ulano’s very popular emulsion
http://www.ulano.com/emulsn/presensitized.htm#qtx (http://www.ulano.com/emulsn/presensitized.htm#qtx)
It lists "Est. 305 mesh BL Speed - 180 seconds” NO WAY IN HELL!!!
Was that white mesh, and a prayer? Was that coated using the glisten method or 1/1 with the sharp edge?
And I know where this may go - yes the pre-sensitised emulsion CAN be used with an exposure calculator (quite accurately and well I may add) if someone cannot see the change the problem is best fixed with a visit to the Optometrist. (Of course I am from the KIWO school of thought on this).
I will likely just buy a scale from Richard at Indy so I can test the results of a scale and exposure calculator as I have abandoned the 21 steps for so long I do not know where my scale actually is...
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Could be we need a clear and agreed on version of what a complete exposure actually is...
I work with this thought, something I picked up when having Dave Dennings help me out.
Full and complete exposure is where the entire layer of emulsion is exposed into a stencil and the entire thickness from face to well side is linked and will not wash off with water (well side where scumming often comes from).
This does not into account any edge thickness inconsistency from the scoop coater edges.
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Full and complete exposure is where the entire layer of emulsion is exposed into a stencil and the entire thickness from face to well side is linked and will not wash off with water (well side where scumming often comes from).
Then somebody needs to start making truly clear inkjet film for use on the newer generation epsons. Or an affordable imagesetter that uses clear film. Or an affordable cts system. With the milky "waterproof" stuff this is unattainable wherever the positive film is in contact with the stencil. Well, I guess it's attainable if you're willing to wrangle the massive gain from laying down that much ink on your positive I suppose....
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Full and complete exposure is where the entire layer of emulsion is exposed into a stencil and the entire thickness from face to well side is linked and will not wash off with water (well side where scumming often comes from).
Then somebody needs to start making truly clear inkjet film for use on the newer generation epsons. Or an affordable imagesetter that uses clear film. Or an affordable cts system. With the milky "waterproof" stuff this is unattainable wherever the positive film is in contact with the stencil. Well, I guess it's attainable if you're willing to wrangle the massive gain from laying down that much ink on your positive I suppose....
Do you have to use the “waterproof” stuff - I switched to the hybrid inks and use the clear.
“Affordable” is dependent on your needs and numbers... when we bought our imagesetter we paid over 45k for it and paid for it in less than three months of use (savings only - increased production was less than a month).
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I use one of these:
(http://2.imimg.com/data2/KX/DH/IMFCP-2750468/ulano-20expo-20calc-500x500.png)
First I lay a piece of the frosted waterproof inkjet film on the exposure glass.
Then I do three-stepped exposures with the calculator - near the top of the screen, the first exposure at 100% of what I think the correct exposure is, then at the middle of the screen at 150%, then near the bottom at 200%.
Since the calculator has 5 steps of neutral density filter, I get approx 15 exposures (with some over-lap) to work with. I cross reference the best of the three and average out the best one.
Since I've laid down a piece of blank inkjet film under all this, the exposures are usually very close.
I typically add about 5% to whatever is calculated. I use diazo or dual cure so I have the extra exposure latitude to work with - the extra 5% never hurts.
With all the above as my procedure I've been able to dial in the exposures pretty quickly and accurately. Now I'm just searching for the perfect water resistant emulsion.
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Indy, talked to Richard, have a 21 and will start testing and comparing with the KIWO exposure calculator and will report the results when I have time to go over this (possibly the next class).
Part of our problem could very well be the issue with some (not-so) professional “screen printing experts” who are clearly giving out erroneous information (a testament to doing something for 50 plus years wrong continues to be wrong each and every year and never improves). We have some real drama queens and parasites in this industry.
In a sea of ignorance the island of simple competence is a glowing oasis.
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The key use of the Stouffer T2115 is to help judge the cure or hardness (resistance to dissolving) of a stencil - not judging the fineness of line or copy properties of your image. It's a tiny positive that could last a lifetime and should be on EVERY stencil you expose so you can prove to any boss that you exposed screens equally or properly. It's accountability. It costs US$10. What do you have to lose?
Plastisol ink is like salad dressing and doesn't attack under exposed stencils - but water-based and solvent inks will break them down in minutes. Completely cured stencils reclaim easily, underexposed stencils don't. Once you can make a durable stencil, then it's time to graduate to refining your copying skills with an exposure calculator.
I've been fielding screen making questions for the last 30 years and only one question in 100 is about reproductive problems.
I've written and spoken for those thirty years that "Since every exposure unit will choke fine lines and halftones, the best art department understands how to tune/calibrate fine lines so they survive the screen making and printing process. If you want to print a 0.030" line on a shirt, you may have to use a 0.045" line. Art (in their ivory tower air conditioned room sitting on comft chairs), can make it easy for printers & screen makers to do their job, rather than expect screen makers and printers to FIX art with under exposure or printing tweeks and tricks".
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Doug I have been messing with the TLX emulsion I got. I printed out my own eight step step wedge test for it, I wanted to use a step wedge test from my own printer to get more accurate results with my own printer. The problem I am having even after the step test I cannot get a full exposure no matter what time I advance to, remember I am only using a UV exposure unit. Tho i cannot get a full exposure I still get good actually very good stencils all be it it takes twenty minutes, even tho the stencils are coming out really nice I have to fight the scumming and poor wash out. I am going to retire the emulsion because i am convinced its not viable with a UV light source. Hope fully soon we will have a new MH unit in its place?
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I too use this model Stouffer grayscale strip, Richard told me to start doing it years ago. With an integrator and other controls in place you don't actually need it on every screen. The above post really lays it out as to why you would have one of these around.
To calibrate exposure I actually have a slightly laborious but very effective practice:
- grid out 9 boxes on a fresh screen with a sharpie or blockout pen
- now, using your best estimate pick a low and high ltu value and number the squares with these values
- place the stouffer strip, with a strip of your positive material behind it, a 0-100% strip about the same size (made on your film outputter) as well some text and stroke lines at various points again, from your printer that you use in production, not someone elses
- move this operation from square to square, blocking out the others with some ruby lith or whatever's around and exposing at the light values for each square
- resolve as you normally do and do it as aggressively as usual
Now you've got nine options that, if you had a good estimate of where the emulsion was going to expose properly, will allow you to find that sweet spot between complete stencil exposure through to the squeegee side of the screen and detail.
If you use your own output device and imitate your device by placing the clear piece of film behind the stouffer strip you're now confident of what %'s will hold on an (almost) fully exposed screen of various mesh/emulsion combinations and can use this information from art generation on down the line.
A step wedge is faster but this is the most accurate method I've arrived at and gives you full control over the calibration.
I've mentioned it before but it's literally not possible to "fully" expose some stencils with the milky "waterproof" films and still hold your detail. So, until some better tech comes out regarding this you need to find that place in the middle and hang out there. Post exposure, while it should be needless is a real saving grace when using these films.
Doug, did you say that yer using clear film on an Epson? If so I really, really want to know how to set this up!
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Indy, talked to Richard, have a 21 and will start testing and comparing with the KIWO exposure calculator and will report the results when I have time to go over this (possibly the next class).
Part of our problem could very well be the issue with some (not-so) professional “screen printing experts” who are clearly giving out erroneous information (a testament to doing something for 50 plus years wrong continues to be wrong each and every year and never improves). We have some real drama queens and parasites in this industry.
In a sea of ignorance the island of simple competence is a glowing oasis.
I hope your statements here coming right after my post are a coincidence and not directed my way...
???
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Indy, talked to Richard, have a 21 and will start testing and comparing with the KIWO exposure calculator and will report the results when I have time to go over this (possibly the next class).
Part of our problem could very well be the issue with some (not-so) professional “screen printing experts” who are clearly giving out erroneous information (a testament to doing something for 50 plus years wrong continues to be wrong each and every year and never improves). We have some real drama queens and parasites in this industry.
In a sea of ignorance the island of simple competence is a glowing oasis.
I hope your statements here coming right after my post are a coincidence and not directed my way...
???
Goodness no...
If I lay into someone I will do it directly - you will find that I don’t often lay into someone - actually I almost never. I prefer to have a conversation where both the other person and myself learn something.
I was more explaining how Richard and I were having a short conversation about how the 21 is promoted and is far too often abused and misused. This misuse is promoted and I abandoned the 21 because the directions given by some are very, very, wrong. I have a problem supporting anything that causes problems for the process for others.
Now with Richards updated information I will progress with this and see if we can make things better for others in the industry - simple, yes?
It may well work out that the use of the scale and the exposure calculator both in conjunction my end up as my position - we will see.
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Doug I have been messing with the TLX emulsion I got. I printed out my own eight step step wedge test for it, I wanted to use a step wedge test from my own printer to get more accurate results with my own printer. The problem I am having even after the step test I cannot get a full exposure no matter what time I advance to, remember I am only using a UV exposure unit. Tho i cannot get a full exposure I still get good actually very good stencils all be it it takes twenty minutes, even tho the stencils are coming out really nice I have to fight the scumming and poor wash out. I am going to retire the emulsion because i am convinced its not viable with a UV light source. Hope fully soon we will have a new MH unit in its place?
When you say UV light source, exactly what unit are we talking about?
What emulsion are you using as your “comparison” to this one?
Humidity?
Are you sure the tub of TLX you received was in date and had a good bottle of diazo?
The biggest problem with any emulsion is the fact that we are dealing with multiple variables and they are all intertwined, identifying the exact problems can get tricky over the phone or internet.
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Doug, did you say that yer using clear film on an Epson? If so I really, really want to know how to set this up!
I just use one of the inexpensive clear films and converted my Epson to the “hybrid” inks. Just the other day I had a student switch from his standard Epson ink to this ink and his problems with burn in exposure disappeared.
While underexposure is without a doubt the most widespread and common problem out in the wild, I would say poor quality positives are in the top 5 most common frustrating problems.
Poor positive v. good quality positive is like night and day.
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Off subject, but Doug, it was nice to meet you. I wish I would have had more time to talk. Vendors think the shows are too long, and the attendees think they're too short!
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Doug, did you say that yer using clear film on an Epson? If so I really, really want to know how to set this up!
I just use one of the inexpensive clear films and converted my Epson to the “hybrid” inks. Just the other day I had a student switch from his standard Epson ink to this ink and his problems with burn in exposure disappeared.
While underexposure is without a doubt the most widespread and common problem out in the wild, I would say poor quality positives are in the top 5 most common frustrating problems.
Poor positive v. good quality positive is like night and day.
Details man, details. What do you mean by a "hybrid" ink, a pigment/dye combo? I would love to go back to using a truly clear positive film. These days it's really all close to the same cost, regular v. "wp" but for me it's all about decreasing the light scatter/blocking.
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Perhaps something like this? http://store.inkjetcarts.us/screen-positive-black-hybrid-ink-p4487.aspx (http://store.inkjetcarts.us/screen-positive-black-hybrid-ink-p4487.aspx)
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Perhaps something like this? [url]http://store.inkjetcarts.us/screen-positive-black-hybrid-ink-p4487.aspx[/url] ([url]http://store.inkjetcarts.us/screen-positive-black-hybrid-ink-p4487.aspx[/url])
That is the one...
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Off subject, but Doug, it was nice to meet you. I wish I would have had more time to talk. Vendors think the shows are too long, and the attendees think they're too short!
Too bad the show got hectic.
Next time we can get together board members for each show for dinner or something.
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Thanks Doug and thank you Sir Frog for the link. Nice price on that stuff too. I think I'm going to start up a new thread about high-line count film positives and contemplate having the time to switch inks and films and do all that fun, aforementioned stuff again.
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I have always known underexposure was very widespread among screen printers but we've never had an issue with it. I'm not saying we never underexpose, I'm just saying that it's never been one of those variables that has given us problems. We have used several different types of "exposure calculators" when an emulsion rep would come in and we were trying out a new emulsion, but I've never used one other than those very rare occasions, 3-4 times in 5+ years. We've never had emulsion locked in a screen during reclaim or any of the other problems that underexposure causes. I'm sure if we looked at every stencil through a loupe, we would find areas that needed improvement, but out of all the issues we've faced over the years, this hasn't been one that we have dealt with for whatever reason. We have a seriously badass exposure unit, 10K metal halide so maybe that's one reason it's not an issue for us, or maybe it's something else, but I'm sure it's mostly due to us never having used an inferior light source. We have had our share of other shops come by and let me burn a tough stencil for them, several dozen times over the past few years but I don't think it's our knowledge of the stencil making process that is superior, I think it's our light source.
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That is a one bad-ass light source Alan. 10k? Sounds glorious.
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I have always known underexposure was very widespread among screen printers but we've never had an issue with it. I'm not saying we never underexpose, I'm just saying that it's never been one of those variables that has given us problems.
...I think it's our light source.
No problems with exposure would make you 1 out of 100 shops and I think Richard would back me up on that - for you this is a good thing.
It could be your exposure light, but I have seen problems with big units in shops also - the problem is not exactly the unit used but the lack of information that person may have.
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Sorry Doug I was vague.
We use a Vastex Exposit, i have used it for almost 15 years now and consider my self quite adept at making quality screens from a low end light source.
Normally I am using QLT, with 4 minute average exposure time with very little room for error. The TLX seems like I could expose it for ever and still have a non fully developed screen. Again i blame that on the light source it is just not a good mix of tools. Fortunately I only mixed half the other half should be fine to use again after we get a new exposure unit.
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That is a one bad-ass light source Alan. 10k? Sounds glorious.
It is glorious, and it's one of those things that I don't appreciate like I should because it's all I've ever known. I've never had to expose a screen with anything else. We did jump from a 5K bulb to a 10K a few years ago, but that's the extent of my exposure unit experience. I know there are lot's of cheaper alternatives for exposure that will produce satisfactory results but I think the $2500 we paid for our unit was worth every penny. I know from reading the forums for so many years that the light source is usually one of those tools that is somewhat skimped out on. The shop with the single point metal halide is probably in the minority by a long shot. I can see how lot's of people can justify going cheap in this area because of the results you can get with some flouro bulbs or halogen work light but I love our unit and I don't think we could ever go backwards or down in our light source. I can't say for sure since I've never used anything else, but never having to worry about some of the things that are very common problems at other shops is a nice thing, especially when it comes to exposing our screens. We use a pure photopolymer emulsion and coat heavy for our lower mesh screens and our exposure times are very fast, under a minute for most everything. 305's with a 10% EOM will expose in around 15 seconds with a new bulb. Our unit also has a light integrator so we use light units instead of time so I can't say exactly what our exposure times are.
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Sorry Doug I was vague.
We use a Vastex Exposit, i have used it for almost 15 years now and consider my self quite adept at making quality screens from a low end light source.
Normally I am using QLT, with 4 minute average exposure time with very little room for error. The TLX seems like I could expose it for ever and still have a non fully developed screen. Again i blame that on the light source it is just not a good mix of tools. Fortunately I only mixed half the other half should be fine to use again after we get a new exposure unit.
With some additional information...
When was the last time you changed the unfiltered UV bulbs? (they should be the unfiltered BL bulbs). They will put out light in a rather consistent way, but the output drops enough at 700 hours (or less) they should be changed once a year in the average small shop.
With any FL tube unfiltered UV bulb exposure unit with the correct glass to bulb setup I would expect about 15 to 21 min of exposure with TLX and 21-28 with darker dual cure emulsions. This is tested with an exposure calculator for a full and complete exposure (no change) and sounds excessive - well it is the nature of the beast - you want a full and complete exposure it takes time with the low power units.
I would wager that your QLT would show underexposure and that type of unit when tested for a complete full total exposure with an exposure calculator - this btw would be using the “glisten or shine” method of coating screens (high EOM).
It is news that is distressing to many because often they are told that your emulsion will expose in less than 2 min. on units like that - it will not give test results that match even close to that... :o
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That is a one bad-ass light source Alan. 10k? Sounds glorious.
I have a 10k as well, Hugh at Richmond told me the bulbs were originally used for landing lights on planes.
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21-28 minutes on a sensitized emulsion? Gawd, that is a real surprise to me. Makes me wonder how anything got done way back when our first unit had a 500 watt halogen bulb.
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21-28 minutes on a sensitized emulsion? Gawd, that is a real surprise to me. Makes me wonder how anything got done way back when our first unit had a 500 watt halogen bulb.
Want a full and complete exposure with a thick coating of emulsion... well it takes time with a low power unit...
Did you use newsprint to blott the backs of the stencil back then to keep from having issues with scumming?
The reason underexposure is so common is that the first section of time penetrates the deepest for exposure of the stencil facing the light. As you go deeper less light energy is received by the emulsion as what is in front creates a filter for the emulsion in the back. Deeper you go the longer it takes for the linking to complete.
Most printers were and are just glad it makes it to the threads of the mesh to half-hang-on for its “life” by the “fingertips" in a way.
Note the variables.
Thick coating of emulsion - thicker than you would see most of the time in the wild.
Low power light unit - inexpensive and smaller but with less power (translates to longer time to expose).
Full and complete exposure from front to back 100% linkage, easier to reclaim, will last for thousands on thousands of impressions with plastisol inks.
And If I forgot that was 230 mid thread mesh dyed with the glisten/shine method, rounded edge of the coater (3/2 most common).
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21-28 minutes on a sensitized emulsion? Gawd, that is a real surprise to me. Makes me wonder how anything got done way back when our first unit had a 500 watt halogen bulb.
One of the reasons most do not want to talk about exposure out in the wild, the variables are huge and the weak lights take longer - much longer than most would expect.
I have tested this with all of the most common tube units out there and using the same emulsions the results are all within about 2 min of each other - the only bulbs like this faster are the very thin bulbs packed tighter into the unit.
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That is a one bad-ass light source Alan. 10k? Sounds glorious.
It is glorious, and it's one of those things that I don't appreciate like I should because it's all I've ever known.
I had the pleasure of using a 10k Richmond back at Logos and IT IS glorious!!
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Where do you guys get non-waterproof film?
most of my suppliers stopped carrying it, I think a lot of my problems come from that.
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21-28 minutes on a sensitized emulsion? Gawd, that is a real surprise to me. Makes me wonder how anything got done way back when our first unit had a 500 watt halogen bulb.
Did you use newsprint to blott the backs of the stencil back then to keep from having issues with scumming?
You bet. I'm not sure we knew that was why we were using newspaper though ;D
I think we used to use Ulano FX88 emulsion back then, we dried the screens in the shop air on shelves wrapped with black plastic! I'll bet they never fully dried, ever.
Our vacuum blanket was a piece of glass and various large phone books for good measure. Washout was risky business, you just hoped and prayed the design would not blow off the screen. We got our Richmond about 15 years ago, I can't even phathom not having it today.
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Douglas and Mike, do you guys recommend non-waterproof films for the 3000? I have a 1K mercury vapor unit. I noticed that the film doesn't let as much UV through and there is a box where the film sits--no matter how long they are exposed.
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I have a Violux 8002T picked it up used for stupid$$$$. Gotta plug the Douthitt people. Super helpful even though I did'nt buy it from them. Walked me through the wiring and proper set up and programming ( its not rocket science but its a bit tricky if you don't have a manual). Then sent me the link to the manual. Even discovered my screen peeps had it set too far away from the vacum table after talking to Mark. So its not a sexy new totally enclosed unit but for under $1,000 I can shoot three auto screens in just over a minute (diazo emulsion)
I like those #s
tp
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Douglas and Mike, do you guys recommend non-waterproof films for the 3000? I have a 1K mercury vapor unit. I noticed that the film doesn't let as much UV through and there is a box where the film sits--no matter how long they are exposed.
I was neve a big fan of the “waterproof” films with a vac and humid conditions even the waterproof will end up sticking to the stencil and when removed will ruin the positive (so what it is a cost of business), and yes the non-waterproof stuff is available.
Would someone out there who has a supplier let us know who has it in stock?
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Two sources that I knew of, Film Source and Screener's Choice have both dropped it. Film Source still has clear film but do not tout it for burning screens but rather for displayed transparencies. Screener's Choice appears to have only WP, so yes, a good question.
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It looks like Tech Support carries it.
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PerformanceScreenSupply.com advertises both WP and Non-WP, and on the next page of their cyber-catalog they offer a CLEAR ink-jet film and a CLEAR laser film. I've not dealt with them, so I'm not necessarily "encouraging" anyone to do so.
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This re-packaged kimoto film from Westar is the best non-wp film I found for the 3000. The key is that Westar is consistent with it. They don't just jump from supplier to supplier and re-brand it.
http://www.westarsolutions.com/vend/westar/westjet.html (http://www.westarsolutions.com/vend/westar/westjet.html)
Directly opposing my opinion regarding toaster pastries, I think frosted film, even lightly frosted, sucks. My take on this is that you get the frostiness as a by-product of building up the emulsion side of the film in order to quickly absorb and dry inkjet ink. "wp" film does a good 'ol job of that for sure and you see a lot less gain out of the printer while still getting adequate d-max with the wp.
With non-wp film you get that crystal clear but the inks tend to flood up the film a little more to get the opacity or d-max you want.
So to me it's a trade-off between:
A more accurate output with less gain but, alas, light scattering, UV blocking, squeegee side of stencil underexposing, frosty bastard carrier sheets.
Less accurate output from more gain but a pleasantly clear and far less troublesome carrier sheet.
I want the best properties of both.
Because after all, your print's only as good as your stencil as your film as your art.
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See, I think the opposite, my printer had banding issues until I switched to WP film, I think I get more gain with WP film than non.
I will check Westar. I think I am going back to non WP.
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Douglas and Mike, do you guys recommend non-waterproof films for the 3000? I have a 1K mercury vapor unit. I noticed that the film doesn't let as much UV through and there is a box where the film sits--no matter how long they are exposed.
I have tried several brands of standard film AND several brands of wp film in the 3000 and the sharpest results are always from the wp film.
I also noticed with some standard films, after being stored for several months, there was some ink bleed into the fine lines of negative space in the films. Like the ink had leeched out and spread out to fill the lines.
I have am Epson 9600 now that I use most of the time and my 3000 is for backup. I only use it for less detailed work or simple text. The 9600 with stock inks through Accurip makes perfect films. I've dialed in my exposures with a 1200w metal halide (MSP 3140) so the frosted wp films are no biggie. (Fixxons) Wp film used to give me some headaches with a less powerful exposure unit (banked fluorescent) because there was no integrator and I had to re-time the thing every couple months.
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I've gotten the same thing with WP film. After a while the edges blur, to the point that there is no way to use them.
Non-WP films are pretty much single use. It's not worth it to store them for any length of time. And at $1 a sheet and a few cents in ink, it's easier and usually faster to print new ones.
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Here's the thing about the 3000- I got excellent, really almost perfect films on the Westjet film I linked to, with my own setting via the original epson drivers or, on the mac, with some gutenprint settings I worked out. No banding, no excess ink, no rough edges. Problem was, I had no rip to run a separations base workflow and had to manually breakdown each files color seps and, if I wanted dots, bitmap them in photoshop, replace in illy and then, after all that, print each file one by one. This is not an appropriate workflow for a busy shop obviously. And, without getting all up in some color profiles and massive curves adjustments natively in photoshop you don't have much for dot gain control. This is an issue on the non-wp film.
None of the rips I trialed could get as good of a film out of the 3000 as the above did, on any brand of either wp or non-wp film, and I think it's because nobody that I know of has written a rip that takes advantage of the the 1440dpi setting on the 3000. Understandable I guess, it is a pretty damn old printer so why bother. I sucked it up and moved on to a 4800. If I had a rip that got me that film quality on the 3000 I might never have left it but I got tired or screwing around with it. Networked, they actually do pretty darn good for themselves compared to the new models. It's hard to beat the roll feed/paper cutter deal on the 4800 though and the custom print size settings with Accurip- check yer overprints, go to the dialogue and check the spot colors and print size, hit print and go do something else.
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go to the dialogue and check the spot colors and print size, hit print and go do something else.
EXACTLY.
Epson needs to make a modern roll-fed, dye-based high resolution printer for separations. 17" wide. One with a SINGLE bulk tank of black and no color channels.
I can dream right?
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go to the dialogue and check the spot colors and print size, hit print and go do something else.
EXACTLY.
Epson needs to make a modern roll-fed, dye-based high resolution printer for separations. 17" wide. One with a SINGLE bulk tank of black and no color channels.
I can dream right?
About three years ago an Epson tech Rep contacted me about “all of this screen printing positive stuff” and wanted to sit down take notes and ask questions. He had traveled to the SGIA just to find out about this “thing” going on with “his” printers.
I suggested something similar to the above, I talked to him several times over the phone when he called to ask more questions, I think it was on the company radar and they ran it by the numbers guys who figured the company would not make enough money over the products they already make and just shelved the idea.
They already make the printer, someone else is making the RIPs and the film, someone is selling inks and they can stay out of the industry for customer service and continue to be a player in simple sales.