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screen printing => Screen Making => Topic started by: Binkspot on November 27, 2012, 06:16:30 PM
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I have been messing around with the CCI WR-25 and Saatichem DW with what I would consider great results. One thing I have noticed with both, a clear residue in the image area random places. I can not see it when the screen is wet and once dried its tougher then nails and usually wont come out until reclaim. I have had to reburn a few screens because of it. Tried screen opener, MEK, thinner etc. The only thing that will take it out is the spot gun which usually freaks up the stencil or worse yet put a hole in the screen. I activate the emulsion the night before I plan on using it, mix slowly with a drill mixer for about 10-15 min while slowly adding the diazo. Then I will hand mix it before each use about 30 min to an hour before each use. If I rinse the screen after blowing out the image for what I would conside an excisively long time the screen is fine. Is the diazo causing this. Do I just need to rinse a little more. Is this normal. Am I doing something wrong. We have used diazo emulsion before but never had trouble like this.
What are some of the other emulsion shops are using, any recomendations to use with plastisol and discharge?
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Sounds like underexposure. Diazo needs a lot more light than photopolymer. A lot lot more.
We use Aquasol HV for plastisol and discharge (post hardener long runs. No complaints.
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sounds like scumming from underexposure. The emulsion is still left in the image but the color is washed away. is the back of the screen "sudsy" like soap bubbles? try water. should take it right out.
we are back to aquasol hvp. left it for a year or so but it's just too damn good to try anything else.
oop -eb beat me to it
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..sounds like plain ol scum, usually from the squeegee side and a result of underexposure. I switched to CCI WR25 recently, and yeah , the exposure time can feel painfully long, ESPECIALLY if you are coming from photopolymer use. It is also kinda hard to develop post-burn, making you think even more that perhaps you have overexposed, but thats not the case. Play with your exposure times, its REALLY hard to overexpose that stuff. Also, when developing, I use a pressure wash on the print side, then flip it over for a flood-type rinse with a regular hose on the squeegee side. It helps wash away what little underexposed emulsion you may have left, which is whats causing that scum.
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Exactly what eb said, beat me too it. We use nothing but Aquasol HVP for everything we run.
You are experiencing "scumming" from underexposure on the squeegee side of the screen which is microns further away from the light source than the print side is. You can solve it by:
1. Dialing your exposures in to where you have close to full light penetration of the stencil and are still holding detail.
2. Flood rinsing both sides of the screen very thoroughly after resolving and padding dry with some paper shop towels.
Option 1 is limited in that, if you use the milky wp film, you'll hit a wall where you are losing finer detail in exchange for complete exposure. A DTS or crystal clear film would solve this. This option is also limited by the strength of your bulb. I would struggle to achieve this without our 5k watt setup.
Some might snark at Option 2 as a "band aid" or newbie thing to do but it's a quick fix and a solution to holding finer detail on thicker stencils. There are some coating techniques we use that always result in a slightly underexposed squeegee side with wp film.
In any case, it's not a bad idea to either pat down the stencil, blast it with some clean, compressed air or vacuum it after resolving. Next, get them horizontal and into a dry box asap so there is no opportunity for the underexposed emulsion scum to run into your image. Then you are speeding up the drying of the stencil so it could go on press quicker. It's essential that your wb stencils are completely bone dry before going on press.
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Unerexposure..
Keep adding time/light until you can no longer see a color change in the emulsion where the film was/wasn't. This line will be very pronounced when underexposed and rinse water in wash tank may appear yellowish as this is diazo washing off.
Once you hit the right exposure, back off to maintain detail on fine line images.
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You will also have premature breakdown on press with the under exposure so be aware of that. I tried CCI WR25 and I could not get it to work half as well as Aquasol HV.
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KIWO DISCHARGE, I use it for EVERYTHING. Photopolymer and it exposes for me in 22 ltu.
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I have had the same issues before, and like everyone else, its underexposure. no matter how much you rinse, the scum or leftover wet emulsion mixed w water runs back into the image and drys in the image.
you can see it on the squeegee side of the screen as youre developing, the water rinses off with a yellowish tint to it.
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Thanks guys. From the effects you are all describing its got to be under exposure, you are right on the money. I was getting a little scared this might just be one of those nature of the beast things. I did two burns with the exposure calculator and added a little but guess I'm still a little off. Back to some test burns.
I am shooting 156 coated 3/2 for 120 ltu on our 3140 (1200w?), clear films. Am I close, yes no maybe. I know everyone will be a little different, just trying to dial it in and make this switch as painless as possible.
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KIWO DISCHARGE, I use it for EVERYTHING. Photopolymer and it exposes for me in 22 ltu.
I still haven't tried any of that. I've sampled the Kiwo 300WR (I think that's what it's called) and it was fine. I still haven't had anything work as poorly as the CP Tex and as good as the WR25. I'm at about 25 light units for our dual cure emulsions which feels like an eternity compared to PP that exposes in 6-8 light units.
Back in the day when we were underexposing everything and those symptoms you're experiencing were an every single day occurence at our shop. That's where the compressed air stage came in at our shop. We were getting the scum in the image area and drying the hell out of it as quickly as possible kept it from happening. Finally we figured out the real issue and the only time we have to worry about underexposure is if we are trying to or if we're testing new emulsions.
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we have been using the kiwo discharge for the last 3-4 months and we LOVE it.
It exposes fast. Holds amazing detail. Holds up to waterbase and discharge fantastic. Strips super easy.
we have been blowing through it, and have only had screens wash out, or not expose, because we are still learning how to expose certain meshes and details with our new exposure unit!
but it rules.
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Sounds like underexposure. Diazo needs a lot more light than photopolymer. A lot lot more.
We use Aquasol HV for plastisol and discharge (post hardener long runs. No complaints.
Exactly the same here
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Who does the white glove test? If you expose your screen and then get it wet in the washout booth you should not have any color from the emulsion come off on a white glove on the squeegee side of the screen. I have never done it but it makes sense.
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Who does the white glove test? If you expose your screen and then get it wet in the washout booth you should not have any color from the emulsion come off on a white glove on the squeegee side of the screen. I have never done it but it makes sense.
Not with a white glove but my finger. I will swipe a screen on the squeegee side often to see if it's underexposed.
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Coating 3x2 with diazo on a 3140 will be closer to 250 -300 ltu's.
A 1x2 coat will expose in the 150 ltu range.
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Coating 3x2 with diazo on a 3140 will be closer to 250 -300 ltu's.
A 1x2 coat will expose in the 150 ltu range.
150 is about where I run 195-230 2/2 with standard WP film on the same unit.
Is there a particular reason why you are running a 156 3/2 Brian?
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I think at some point your emulsion should be like your white plastisol.
Choose one and stick with it.
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Thats what I do. If it works for WB then it works for everything else. Diazo so a bit slow but I'm shooting 4 up. Use a pressure washer to rinse, squeegeee off excess water and then hit with 90 PSI of air. Screens are practically dry before the hit the rack. After about two minutes ready for blockout.
Hence the eighty screens in eighty minutes (Oh no I didn't!)
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Well, that's two shops I respect that have compressed air in the screen room. Might have to look
into this.
Anyone have experience with the wet/dry vacs and a water sucker screen safe attachment?
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Well, that's two shops I respect that have compressed air in the screen room. Might have to look
into this.
Anyone have experience with the wet/dry vacs and a water sucker screen safe attachment?
Sean am I one of the shops you respect? I have used compressed air in my washout process since I started. It works great on 305 screens with high detail. Plus it speeds up the drying time.
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Well, that's two shops I respect that have compressed air in the screen room. Might have to look
into this.
Anyone have experience with the wet/dry vacs and a water sucker screen safe attachment?
Sean am I one of the shops you respect? I have used compressed air in my washout process since I started. It works great on 305 screens with high detail. Plus is speeds up the drying time.
been doing this for 15 years!
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Didn't know you did too John. But yes.
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Well, that's two shops I respect that have compressed air in the screen room. Might have to look
into this.
Anyone have experience with the wet/dry vacs and a water sucker screen safe attachment?
That will work very well also. Majestech used to make an aluminium tube with a slit in it but somewhersomeone posted a how to make your own version. The ones that come with the shop vac work but, as they are plastic, get dinged pretty quickly.
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Compressed air in the screen room is a must. Prevents any drip action from drying in the image area. And speeds up the process a lot!
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I have compressed air in the screen room, but that's not what we use, we use one of these to get 90% of the water off:
(http://www.epoxysuperstore.com/store/images/Squeegee-Back.jpg)
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Thats what we use but follow up with air
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Using air here since day one as well.
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we use air too, and I made one of those squeegie deals out of an old windshield wiper. . .made a handle out of conduit. . .ghetto fabulous but it works like a damn champ. . air helps a ton, just make sure you get a filter on your airline of you'll be blowing dirty oil air all over your screens.
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Hey Brian here is a real down and dirty band aide but it may save a screen or two. If when you get dried in scum one of two things will soften it, water or emulsion remover. Many years ago when we sucked at screens I would get scum out with hopefully water first then if not try to dab some emulsion remover carefully where the scum was let it soften up the scum then clean out quickly, if an edge was effected then try to band aide it with tape. I know real ghetto but hey no one learned everything in a day.
We always blow our screens out with air, if it has fine details use distance to lower the pressure but pretty much a well developed screen will hold its edge when hit with the air.
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Oh yea since I have the same expo I would bet your exposure should be closer to 200 ltus than 100 using diazo.
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Thats what we use but follow up with air
Exactly how we do it. 18" window squeegee on both sides gets most of the water off then hit it with the compressed air and the screen is ready for tape within minutes after the washout booth.
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Alan did you ever try that squeegee I sent you the link for.
My guy still keeps squeegeeing everything because he's so impressed with it. LOL
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Thanks again for all the input. It has been an interesting week to say the least and have made some discoveries and changes to the screen making process. I know some of this is off topic but it is all related.
After this thread took off I went back to the shop and started playing again. Adjusted my exposure times with much better results, still need to dial it in a little more. But spending 3-5 minutes exposing a screen is not going to cut it around here. I will be keeping my adjusted times where they are at now until we decide which emulsion will work best for us. I have ordered a pail of the KIWO discharge to try. If this works well it is what I’ll use if not move on to the Aquasol HV. We were happy with our current emulsion but needed to change to work with WB and discharge. If we are going to make the switch now is the time for us to do it coming into our slow season and gives me time to play and get it right before we start humping again.
I have been coating 3/2 for the past 7 or 8 months for a better stencil thickness. Most of the stuff we run is contract work that needs to be turned around quickly and usually one to three spot colors, not real detailed work. So that being said I can usually get one hit light or white ink on darks doing 3/2. This keeps the jobs running faster still achieving a quality product and getting more out the door each day. Most of the screens we use are 150-180 mesh for this work although we have everything from 25 to 355.
This got me thinking why can’t I coat 2/1, others do it so I started looking more in detail what and how I was coating. When we first started printing a friend of ours who did some crazy amazing printing showed us how to coat 2/1 and it worked great. Then someone who will remain nameless told us there was a better way so being naive we started coating his way. This is when the things started going south in the stencil world for us. I wasn’t at the shop all the time and they just struggled with it instead of trying to figure out what the problem was and fixing it. When I came on board full time a little more then a year ago better stencils was my first goal. I did my research, watched others coat, talked to a bunch of people at different shops and started coating 2/1 again. As I got better at coating I was trying to achieve the “Best Stencil” and one hit white so I started increasing my coats first 3/1 then ended up at 3/2 and ending up with better stencils. I use four different coaters, one for each size frame. I looked carefully at a bunch of screens, all different frame sizes. I always had real thick stencils on our 20x24 and 25x36 frames but the 23x31’s were always thinner and the quality less consistent even with the 3/2. First thing I did was lay all my coaters on the exposure glass and noticed the one I use for the 23x 31’s was twisted and the lip was higher than the end caps, the other three were flat. So I coated some 23x31’s using the smaller scoop 3/1 and 2/1, dried and burned them. Using a good scoop coater I able to get good results using 3/1. So I picked up a new coater and started playing again. After some experimenting with the new coater I am happy to say we are now down to 2/1 using the glisten method on the 23x31. I have also started coating the other sizes 2/1 with good results. I believe my whole problem with the stencils was the 18” coater. Since that was the one I used most I applied the same technique when coating the other screens. Trying to achieve a thick stencil I was actually doing more harm.
All the screens get the squeegee before leaving the wash out booth. I have used air to blow water out of screens when we are in a rush but always afraid of messing up the screen or stencil. The same goes for the power washer blowing out the image, afraid of messing up the stencil. I do use the shop vac regularly to suck the water off the screen. I will be trying the power washer this coming week to see what happens. Then will run an air line up to the washout booth and start using the blow nozzle. I do need to be careful if others try using the washer and air they do not harm the screen or stencil. All the screens end up in a rack horizontal in the screen room to dry in the winter, outside in the sun during the warmer months. I will also post expose screens after drying in the screen room for longer runs.
Don’t get me wrong I am not trying to reinvent the wheel and once I find something that works I’ll stick with it. But I am always cautiously trying to improve our operation. Bottom line is I just want to make the right choices for our shop and as painless as possible. There is always something new to learn or improve on. Sorry to ramble on like this but just very excited about the accomplishments I have made this past week.
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Don't know if this will help but I have found running a 1/1 to be easier to print W/B discharge through. I had a tough time with a thick stencil.
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Don't know if this will help but I have found running a 1/1 to be easier to print W/B discharge through. I had a tough time with a thick stencil.
agreed! plus you need the hardener even with the kiwo dicharge, I use it. Kiwo dealer will give you a free quart to try.
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Well, that's two shops I respect that have compressed air in the screen room. Might have to look
into this.
Anyone have experience with the wet/dry vacs and a water sucker screen safe attachment?
My M&R sales rep told me they are using windjet air nozzles instead of wet dry vacs. The windjet will dry the screen instantly and you avoid getting all that crap in the screen. We will set this up next year.
http://www.spray.com/spray_nozzles/compressed_air.aspx (http://www.spray.com/spray_nozzles/compressed_air.aspx)