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screen printing => Screen Making => Topic started by: easyrider1340 on September 18, 2019, 10:15:44 AM
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I lurk here MUCH more than I post. I appreciate being allowed to soak up the knowledge from all of you, I’m certainly not in your league!
My question(s) is about stencil making with halftones.
Let’s say, exposure times are dialed in to a 7 on Stouffer scale, screens coated manually, films are dark, using Accurip, 305 mesh, 45 LPI.
Are you able to produce a stencil that looks exactly like your film? Meaning every dot is developed? What is good enough?
I’ve read that it takes high end equipment to get dots below 7-10%. Is that acceptable? I’m a manual, garage, part time shop - just trying to learn and get better.
Thanks so much
Terry
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Light source? I've only ever used point source lights, from Carbon Arc, to Metal Halide, and now Saati's Pro-lite 450. Point sources will make better halftones, but I believe plenty of folks using fluorescent tubes get it figured out, maybe some will chime in. At 45 lpi, on 305, you should be able to get most every dot. As for getting the dots on the screen the exact same size as the film, you should be very close, but even so, when you print, they will gain size, which of course teaches us how to compensate.
Steve
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Thank you for the response. I currently use a 50 watt LED that is a DIY. (I have an E200 on order). I also have a fluorescent tube exp unit that I started with.
I will post last nights exposure example in a moment.
Light source? I've only ever used point source lights, from Carbon Arc, to Metal Halide, and now Saati's Pro-lite 450. Point sources will make better halftones, but I believe plenty of folks using fluorescent tubes get it figured out, maybe some will chime in. At 45 lpi, on 305, you should be able to get most every dot. As for getting the dots on the screen the exact same size as the film, you should be very close, but even so, when you print, they will gain size, which of course teaches us how to compensate.
Steve
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This is 305, PHU2, 6 on scale so underexposed. But the other thing I noticed is emulsion was falling out of the image area during pre-rinse. This is first time I’ve ever used PHU2 (typically used dual cure in past). ...and I used pressure washer to rinse.
So I believe I have 2 obvious issues
- continue dialing in exposure to a 7
- stop using pressure washer
Am I missing anything fundamental?
I really appreciate the feedback. I’ve been printing part time for years, but spot color prints are much more forgiving.
Terry
(https://uploads.tapatalk-cdn.com/20190918/6d09ba14f60225d123939d82bf34cf52.jpg)(https://uploads.tapatalk-cdn.com/20190918/0680d5c5248c214cf457cbc818c50840.jpg)
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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.
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I really appreciate the feedback. I’ve been printing part time for years, but spot color prints are much more forgiving.
Terry
I don't want to nit-pick, nor let the discussion go too far astray, but the more statements like this go un-corrected, the more the terms will be misunderstood.
Spot colors can be halftoned, or solid.
Spot colors are simply colors printed with a single ink, either stock or mixed, rather than colors mixed in and by the printing process. 4 color process, simulated process, index prints, etc.
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I really appreciate the feedback. I’ve been printing part time for years, but spot color prints are much more forgiving.
Terry
I don't want to nit-pick, nor let the discussion go too far astray, but the more statements like this go un-corrected, the more the terms will be misunderstood.
Spot colors can be halftoned, or solid.
Spot colors are simply colors printed with a single ink, either stock or mixed, rather than colors mixed in and by the printing process. 4 color process, simulated process, index prints, etc.
You are correct. And this job is spot colors with halftones. I should have said block-letter, solid block or similar. Thank you.
Terry
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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
http://www.AllegiantGraphics.com
https://www.Facebook.com/AllegiantGraphics
https://www.Instagram.com/AllegiantGraphics
Sent from my iPhone using Tapatalk
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I really appreciate the feedback. I’ve been printing part time for years, but spot color prints are much more forgiving.
Terry
I don't want to nit-pick, nor let the discussion go too far astray, but the more statements like this go un-corrected, the more the terms will be misunderstood.
Spot colors can be halftoned, or solid.
Spot colors are simply colors printed with a single ink, either stock or mixed, rather than colors mixed in and by the printing process. 4 color process, simulated process, index prints, etc.
You are correct. And this job is spot colors with halftones. I should have said block-letter, solid block or similar. Thank you.
Terry
Sent from my iPhone using Tapatalk
Ah, well it was the section you initially chose in which to post, that helped confuse me. I'm moving it to Screen Making
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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?
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Thank you. I have no way to check EOM.
Vacuum is DIY. Not sure it’s good enough.
I’m awaiting delivery of a Vastex E200. Hoping that will help.
(https://uploads.tapatalk-cdn.com/20190918/fe49f045df73317464156d89c7bd4c32.jpg)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?
Sent from my iPhone using Tapatalk
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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.
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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.
This!
When we switched to a LED, we have ran nothing but 1/1 coated screens.
We have yet to have an issue with breakdown and get great dot results (when we have those jobs) in the 5% range.
We use Murakami HVP emulsion with a 7.5 second burn.
I will also agree that the draw down on your blanket could use some attention. That should suck down tight to give good positive contact between the glass and your film.
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a note on vacuum. Really good contact between film emulsion and screen emulsion is probably even more valuable than a point light source in holding small detail. That's why so many folks got (get) great results with fluorescent tubes. Even if the light is coming from multiple directions, good contact helps it from undercutting.
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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
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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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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
http://www.AllegiantGraphics.com
https://www.Facebook.com/AllegiantGraphics
https://www.Instagram.com/AllegiantGraphics
Sent from my iPhone using Tapatalk
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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.
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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
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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
(https://uploads.tapatalk-cdn.com/20190919/97481064918210755e1482a992bcbd30.jpg)
Blue shirt is test on actual garment. Bella 3001 (True Royal)
(https://uploads.tapatalk-cdn.com/20190919/69df99deff19209017a8e5f197d5e757.jpg)
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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
AMEN! Not apples to apples.
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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
[url]http://www.AllegiantGraphics.com[/url] ([url]http://www.AllegiantGraphics.com[/url])
[url]https://www.Facebook.com/AllegiantGraphics[/url] ([url]https://www.Facebook.com/AllegiantGraphics[/url])
[url]https://www.Instagram.com/AllegiantGraphics[/url] ([url]https://www.Instagram.com/AllegiantGraphics[/url])
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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.
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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
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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
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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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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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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.
Sent from my iPhone using Tapatalk
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