Author Topic: Looking for advice on halftones  (Read 3674 times)

Offline 3Deep

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Re: Looking for advice on halftones
« Reply #15 on: September 19, 2019, 10:07:33 AM »
you need a thick enough stencil and a 1/1 might not be it. Slow coat with dull side might be OK.

Wow I can't believe I'm gong to disagree with you there Pierre, but all my testing is in my shop, so it makes a difference.  I coated thicker screens and my LED just didn't do the trick, so 1/1 was perfect, plus I'm thinking I coat the print side first then the squeegee side which I feel push most of the emulsion back to the print side which gives me a thicker print side anyway, I'm wrong in thinking this?,  I've coated s mesh with the round edge of the coater and to me it was just to much emulsion on the screen so I even coat them 1/1 now, seems like the s mesh just wholes more emulsion for some reason.

darryl
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Offline easyrider1340

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Re: Looking for advice on halftones
« Reply #16 on: September 19, 2019, 10:13:51 AM »
You get halftone detail you want to underexpose, 7 on the Stoufer is too high.
You also need to check EOM, it will be hard to hold detail on a thick emulsion.
How good is your vacuum?

I did find a couple leaks on vacuum frame.  Sealed those last night and will reconfirm tonight.  This is a recent DIY build, so I’m still doing testing. 


Terry
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Offline easyrider1340

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Re: Looking for advice on halftones
« Reply #17 on: September 19, 2019, 10:15:47 AM »
From what I see your vac is not pulled down tight enough, if that is a full vac pull down?, I've been told and I think someone mention it here that LED is not really a good light source for thick coated screens...1/1 should be fine, or just increase your burn time.
My emulsion was too thick on mesh.  It was much more difficult to reclaim.  So I recoated 1/1, and I believe I got more detail.  But also found vacuum leaks, which I sealed last night.  Will reconfirm tonight. 

Offline easyrider1340

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Looking for advice on halftones
« Reply #18 on: September 19, 2019, 10:21:57 AM »
Thank you for the advice and questions. 

Vacuum is not tight enough.  Hopefully I’ve resolved that and will retest tonight. 

I “believe” my film is dark enough.  In large areas, you can’t really see light through it. Epson 1400, All Black, Accurip.

Should I bump up LPI 5-10 to get a better representation of 45?

Thanks
Terry

ugh, not sure where to start. . .
you need a thick enough stencil and a 1/1 might not be it. Slow coat with dull side might be OK.
Vacuum needs to be so tight that the film has an oil sheen looking pattern on it. If you don't see it, it's not tight enough. As Darryl said, what you are showing in the picture is not enough!
Film needs to be dark! What are you using to print it? If you look at the lights in the shop through a dark part of the film you should barely be able to see them.
PHU2 manufacturer specifies 7 on the scale. Stick with it. If your film is dark, overexposing is not an issue. Underexposing is ALWAYS an issue!
You should be able to dial in and hold about 5-6% with the specs you mentioned. AccuRIP prints dots larger than advertised, so your 45 lpi is probably closer to 35. A 5% at 35 is a really big dot and you should work on your screens until you can hold it.
The Vastex unit we tested was good to about 5-6% at 55 lpi (calibrated). Due to numerous LEDs it will not be as good as a single point light source. See if they have a MH that is a single point. This is not to say that their unit is bad, just the opposite, it was the best on the market when we did the testing, it would just mean that you are starting with a handicap. If you are OK with doing really good work rather than great work you'll be OK!

pierre

Offline easyrider1340

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Looking for advice on halftones
« Reply #19 on: September 19, 2019, 10:34:28 AM »
This is last nights trial with 1/1 PHU2.  I added weight to the vacuum top to get film tighter.  Found vacuum leak and will try tonight. 


Grey shirt is a test print


Blue shirt is test on actual garment.  Bella 3001 (True Royal)

Offline Dottonedan

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Re: Looking for advice on halftones
« Reply #20 on: September 19, 2019, 04:33:47 PM »
AccuRIP prints dots larger than advertised, so your 45 lpi is probably closer to 35. A 5% at 35 is a really big dot and you should work on your screens until you can hold it.
pierre


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Offline tbarnes

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Re: Looking for advice on halftones
« Reply #21 on: September 19, 2019, 05:39:07 PM »
I may have a coating issue.   I coated 2/1.   Maybe emulsion was too thick thus losing the detail. 

I don’t have a method (that I know of) to measure EOM, but maybe I should try a 1/1 to see if that grabs the detail. 

I really think underexposed and the pressure washer compounded my issue. 

But my original question was answered, and I should target my process improvement toward holding every detail.   I just wasn’t sure if there was a “good enough”.   I’m sure there are thousands of garage printers who do less research than I on this topic, thus “good enough” is standard.  But I’d like to separate myself so that I have the edge.  If that makes sense. 

I appreciate the advice, and I’ll keep lurking.  :-)

As Steve said emulsion is key for different light source, also when I had my tube unit I used a dual cure emulsion and color mesh, which seem to burn a hold lot better with my halftone work.   I just started using a LED point light which is a 100 watt light and I'm getting better dots at 35 seconds using HXT emulsion, but what I've seen VPR might be a real good emulsion for LED exposure, I heard someone say it's not how long you expose, it's how well you expose the screen.




Terry
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Definitely get the vacuum fixed. Another trick would be to add weight to each side of the frame to create that positive pressure. About 30 lbs or so should work.

What kind of emulsion are you using? When you coat your screen, make sure you are using the dull side and not the sharp side. I suggest doing a single pass on the print side followed by two passes on the squeegee side. If you hold your screen on an angle to the light, it should have a solid sheen to it. That is how you know it has fully encapsulated the mesh.  Make sure you dry your screen print side down so the stencil is thicker on that side of the mesh.

A couple of things to look for when spraying your screen out...if the emulsion is really soft or sticky on the squeegee side after you have let it sit in water for a while, it is under exposed. If it sprays out chunky, it is over exposed. If you over expose it, it will cause halation and the halftones will look smaller than the film. If you under expose it, you risk dot gain and the halftones will look larger.

Hope this helps some.

Offline blue moon

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Re: Looking for advice on halftones
« Reply #22 on: September 19, 2019, 09:36:23 PM »
Thank you for the advice and questions. 

Vacuum is not tight enough.  Hopefully I’ve resolved that and will retest tonight. 

I “believe” my film is dark enough.  In large areas, you can’t really see light through it. Epson 1400, All Black, Accurip.

Should I bump up LPI 5-10 to get a better representation of 45?

Thanks
Terry

ugh, not sure where to start. . .
you need a thick enough stencil and a 1/1 might not be it. Slow coat with dull side might be OK.
Vacuum needs to be so tight that the film has an oil sheen looking pattern on it. If you don't see it, it's not tight enough. As Darryl said, what you are showing in the picture is not enough!
Film needs to be dark! What are you using to print it? If you look at the lights in the shop through a dark part of the film you should barely be able to see them.
PHU2 manufacturer specifies 7 on the scale. Stick with it. If your film is dark, overexposing is not an issue. Underexposing is ALWAYS an issue!
You should be able to dial in and hold about 5-6% with the specs you mentioned. AccuRIP prints dots larger than advertised, so your 45 lpi is probably closer to 35. A 5% at 35 is a really big dot and you should work on your screens until you can hold it.
The Vastex unit we tested was good to about 5-6% at 55 lpi (calibrated). Due to numerous LEDs it will not be as good as a single point light source. See if they have a MH that is a single point. This is not to say that their unit is bad, just the opposite, it was the best on the market when we did the testing, it would just mean that you are starting with a handicap. If you are OK with doing really good work rather than great work you'll be OK!

pierre

stay where you are until you get 5% to open. Than add 5 lpi and work on getting the 5% to open again. Keep bumping along as you get better. . .

pierre
Yes, we've won our share of awards, and yes, I've tested stuff and read the scientific papers, but ultimately take everything I say with more than just a grain of salt! So if you are looking for trouble, just do as I say or even better, do something I said years ago!

Offline easyrider1340

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Re: Looking for advice on halftones
« Reply #23 on: September 20, 2019, 10:06:32 AM »
Not much progress last night.  This DIY project is literally a POS.  LOL. It’s a Frankenstein. 
Fixed a couple vacuum leaks, which caused another couple of leaks to appear.  More sealer and wait for curing.   It did pull down more once the 2 bigger leaks were sealed, so I’m on a path.   ...although the light I see may be a train!

E200 is shipping next week.  (not soon enough)

Thank you so much for the advice.  I truly value the time you all take to post detail about your processes.  Their are nuggets in every post. 

Terry


Online Sbrem

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Re: Looking for advice on halftones
« Reply #24 on: September 20, 2019, 11:31:32 AM »
you need a thick enough stencil and a 1/1 might not be it. Slow coat with dull side might be OK.

Wow I can't believe I'm gong to disagree with you there Pierre, but all my testing is in my shop, so it makes a difference.  I coated thicker screens and my LED just didn't do the trick, so 1/1 was perfect, plus I'm thinking I coat the print side first then the squeegee side which I feel push most of the emulsion back to the print side which gives me a thicker print side anyway, I'm wrong in thinking this?,  I've coated s mesh with the round edge of the coater and to me it was just to much emulsion on the screen so I even coat them 1/1 now, seems like the s mesh just wholes more emulsion for some reason.

darryl

Well Darryl, I coat 2/2 with the sharp side for decades. Like most of us, I developed a touch depending on what count I was coating, and of course, how much was left in the coater before replenishing, as a full coater coats differently from a half filled right? When coating 305 and up, I might have a 2/3 after I inspect it.

Steve
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Offline CBCB

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Re: Looking for advice on halftones
« Reply #25 on: September 22, 2019, 07:58:47 AM »
Tons of good advice in this thread! Emulsion thickness will definitely play a big role here. We coat 1:1 sharp with PHU so I would try that thinner coating as an experiment if you can’t measure the EOM.
Pressure washer is pretty critical in my opinion. If it’s too soft for the washer then you have other problems in exposure. I suggest a good pre-soak of the screens before rinsing though. I swear our halftone resolution is better now that we are using a post-exposure dip tank.

I did want to touch on this note from Pierre though.

Film needs to be dark! What are you using to print it? If you look at the lights in the shop through a dark part of the film you should barely be able to see them.
PHU2 manufacturer specifies 7 on the scale. Stick with it. If your film is dark, overexposing is not an issue. Underexposing is ALWAYS an issue!

pierre

Someone gave me some great info and advice about this one time. Opacity doesn’t have much to do with UV blocking. Think about sunglasses...
And putting down too much ink is going to make it difficult for those halftones to not be gaining. AccuRip does have a wonky default dot curve but it can be exaggerated by other factors like the film and exposure.

My advice for that is to do the density test, and expose it! You’ll see right away which blocks wash out fine.
My experience was that we were at a 12 on the density scale because it was opaque. Tested it and got cleaner detail with less ink and same exposure at a level 4. Dark film is definitely key here but too heavy is gonna give halftone problems too.



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Offline blue moon

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Re: Looking for advice on halftones
« Reply #26 on: September 22, 2019, 08:38:19 AM »
Tons of good advice in this thread! Emulsion thickness will definitely play a big role here. We coat 1:1 sharp with PHU so I would try that thinner coating as an experiment if you can’t measure the EOM.
Pressure washer is pretty critical in my opinion. If it’s too soft for the washer then you have other problems in exposure. I suggest a good pre-soak of the screens before rinsing though. I swear our halftone resolution is better now that we are using a post-exposure dip tank.

I did want to touch on this note from Pierre though.

Film needs to be dark! What are you using to print it? If you look at the lights in the shop through a dark part of the film you should barely be able to see them.
PHU2 manufacturer specifies 7 on the scale. Stick with it. If your film is dark, overexposing is not an issue. Underexposing is ALWAYS an issue!

pierre

Someone gave me some great info and advice about this one time. Opacity doesn’t have much to do with UV blocking. Think about sunglasses...
And putting down too much ink is going to make it difficult for those halftones to not be gaining. AccuRip does have a wonky default dot curve but it can be exaggerated by other factors like the film and exposure.

My advice for that is to do the density test, and expose it! You’ll see right away which blocks wash out fine.
My experience was that we were at a 12 on the density scale because it was opaque. Tested it and got cleaner detail with less ink and same exposure at a level 4. Dark film is definitely key here but too heavy is gonna give halftone problems too.



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agreed, UV blocking is what matters! Unfortunately, we can't see it and most of us can't measure it. So visible opacity is a safe bet. It will also depend on the ink, some have more and some have less UV blockers.

Overall though, CBCB is right, you should try what he says!

pierre
Yes, we've won our share of awards, and yes, I've tested stuff and read the scientific papers, but ultimately take everything I say with more than just a grain of salt! So if you are looking for trouble, just do as I say or even better, do something I said years ago!