# Do you think my problem is exposure time or mesh count?



## brice (Mar 10, 2010)

I just switched to SAATI PV. Ran a test and I appear to have dialed my exposure to about 90 seconds with my unit. Anything over 6 points washes out nicely.

My challenge is the fine detail. When I wash it out, it seems to stubbornly hold and hold. Almost clear, and then, bam, the detail blows out. That makes me think that while I thought I had it dialed in I may still be over exposing and need to shorten it even more. Perhaps light is creeping into the detail. My unit has a lid with a pressure foam pad so I know I'm getting good contact. 

My only other thouht is maybe I need a finer mesh. I'm using 110. Perhaps 156 would have been a better choice. Would this make any difference? Perhaps is my time was a little long, it would hold the detail better?

I was using a diazo emulsion and decided to switch. 

Grasping at straws. Pull a few, won't you?


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## Jsaladin (May 23, 2010)

110 mesh is not going to give you a lot of detail. I would raise your mess count. If it is fine detail you might even need to go up to a 200. What kind of exposure unit are you using?


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## franktheprinter (Oct 5, 2008)

Hi. You should be try at least a 155 mesh...also
make sure your vacuum is performing correctly. You
also want the art on the mesh side and not glass side to give it even closer contact,,,that should help


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## lharlan1972 (Feb 14, 2011)

I would try using at least a 156 or even a 196 mesh count. Sometimes the dyed mesh also works better. I only use 110 mesh for white ink or designs with no detail.

Lesha


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## jsf (Aug 4, 2009)

Basically your 110 will not hold much emulsion and it will easily wash away, like everyone else said do it on finer mesh count. 150 will be just fine but do it on 200 will do best.


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## Geraldine64 (Feb 3, 2011)

We use 110 to 125 for white and bold designs.
160 for most designs 
225 for dots and fine details, thin lines
305 for process.

On 160 and up I use only yellow mesh so that light will not bounce like it does with white mesh. Fine detail won't get undercutting from light source.

The higher the mesh the less exposure time.

So the mesh is one of your problems but the exposure time I'm not sure of.

Geri


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## rbrower (Feb 3, 2011)

Geraldine64 said:


> We use 110 to 125 for white and bold designs.
> 160 for most designs
> 225 for dots and fine details, thin lines
> 305 for process.
> ...


Just wanted to reassure you that Geri's spot on.

I rock a 230 for fine stuff and 305 for 4CP. I only expose for about 90 sec but not sure of your exposure unit so that could be different for you.


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## brice (Mar 10, 2010)

I'll give 156 a shot tomorrow. I have 110 and 156. I'll pick up a couple of finer mesh if I need to. Do you think I need to adjust my exposure time when I up the mesh count?

Thanks for the tips.


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## rbrower (Feb 3, 2011)

All other things being equal. Higher mesh counts usually mean lower exposure times.


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## tpitman (Jul 30, 2007)

franktheprinter said:


> Hi. You should be try at least a 155 mesh...also
> make sure your vacuum is performing correctly. You
> also want the art on the mesh side and not glass side to give it even closer contact,,,that should help


Part of his problem may be the fact that he _isn't_ using a vacuum blanket, but foam with some weight on it.
Ink side of his film against the emulsion with a vacuum blanket on a 156 yellow mesh (or higher) will go a long ways towards eliminating variables that might be contributing to his woes.


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## franktheprinter (Oct 5, 2008)

tpitman said:


> Part of his problem may be the fact that he _isn't_ using a vacuum blanket, but foam with some weight on it.
> Ink side of his film against the emulsion with a vacuum blanket on a 156 yellow mesh (or higher) will go a long ways towards eliminating variables that might be contributing to his woes.


 
Agreed. To get a proper burn with stuff as small as
5pts or smaller you really need a vacuum blanket...
you'd be surprised how much a difference it makes...


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## Diver86 (Dec 6, 2006)

*I'll bet you 'dollars to doughnuts' the problem is 100% due to inadequate film positive opacity.*

*If your positive is not opaque, TOTALLY OPAQUE, you can not hold fine lines AND be able to properly cure emulsion. Undercured emulsion will washout, which is what's happening when he tried to blow out a fine line.*

*If it was not good contact, you could spray water on the screen for half a day and not blow out the image edges. Screens would develope great, but leave sawtooth edges.*

*Diazo emulsion is very fast exposing, so maybe you've been "getting away with it" all this time....*

*If you're using a laser printer to make positives, I'll bet your issue is there. If you're using inkjet, use different film or ink, something is wrong....*


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## brice (Mar 10, 2010)

More testing today and tomorrow with higher mesh count. I'll let you know.


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## cotenc (Feb 14, 2011)

franktheprinter said:


> Hi. You should be try at least a 155 mesh...also
> make sure your vacuum is performing correctly. You
> also want the art on the mesh side and not glass side to give it even closer contact,,,that should help


ya vacuum is key here, and make sure your art is nice and dark. Gray art sucks to wash out...


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## brice (Mar 10, 2010)

It is NOT film opacity. I've been printing for about 9 months and the only change here was my emulsion. I switched from a known emulsion diazo based emulsion to Saati SV (no mixing of diazo needed) and was adjusting my exposure times. My compression lid is working great and keeping my film positive firmly against the emulsion during exposure. No doubt vacuum would be more consistent, but that wasn't my problem here. 

I took a hard look at the failed screens again and my test screen using an exposure calculator. It was borderline as to how far I should take DOWN the exposure. I boosted exposure time in my second test by 15 seconds and bingo. Everything washes out nicely. Both 110 and 156 screens. 

I'm all set. I appreciate all of the suggestions and I'm sure this will be helpful for a printing neophyte or someone else changing emulsions. While they all weren't related they did make a nice checklist of things to check. I'll be more patient when/if I change emulsion again. Don't plan to though. I like the new emulsion.


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## waipahe (Feb 25, 2007)

Bryce, just wondering what kind of exposure times are you seeing with the SAATI PV? I'm using dual cure and got burn times of 1:18 on 230. Just curious. Thanks.


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## Diver86 (Dec 6, 2006)

Bryce
Glad you figured it out so quick. I was 1/2 right . I did say Underexposure. But I blamed the wrong piece of the puzzle 100%. 

Yes that's right..... I "assumed" .... I'll admit it. 

Because this emulsion is so fast, use caution where you dry and store coated screens. It's real easy for them to get "fogged" or a little pre-exposed. 

So, I owe you "doughnuts" on my publicly stated bet! You want Boston creme or jelly?


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## brice (Mar 10, 2010)

I was using CCI DXP dual cure with a Ryonet 20x24 exposure unit with a compression lid and exposing at 4:15-4:30. Now with Saati SV I'm down to just under 2:00. 

Diver, don't remember you mentioning under exposed so we're even . Glad i figured it out so fast because I have a print job due by Friday. Whew.


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## Geraldine64 (Feb 3, 2011)

Good for you.


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## brice (Mar 10, 2010)

Well I thought I had it figured out. This image just won't wash out. I've washed out finer detail on the same mesh count using the same emulsion and exposure time. I've degreased the screens. I've tried to expose and was out this screen at least 4 times in the last 2 days. The hearts won't wash out and when I finally do get the hearts washing out, the letter blow out. I've never had this problem before...

Do you think I might get a better result if I split the image into two screens and printed it separately? Grasping at straws at this point. 

HELP!


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## brice (Mar 10, 2010)

oops, here's the image. Smalles line or area is 4pts.


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## jsf (Aug 4, 2009)

brice said:


> Well I thought I had it figured out. This image just won't wash out. I've washed out finer detail on the same mesh count using the same emulsion and exposure time. I've degreased the screens. I've tried to expose and was out this screen at least 4 times in the last 2 days. The hearts won't wash out and when I finally do get the hearts washing out, the letter blow out. I've never had this problem before...
> 
> Do you think I might get a better result if I split the image into two screens and printed it separately? Grasping at straws at this point.
> 
> HELP!


Exposure problem then, have you tried a step wedge test? I could turn that image out on a 100 mesh with no problem. What you are experiencing now is an over-exposure. Btw what is your exposure setup built with?


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## brice (Mar 10, 2010)

Over exposure? Really? I used an exposure calculator. My test exposure was 3:00 and it indicated I had to reduce exposure by 1/2. I'm now exposing at 1:30. I'm using a Ryonet 20 by 24 with 130 watts of unfiltered UV about 8" from the screen and mask. There is a compression lid on the unit and I'm getting excellent contact. As I said I was able to expose finer detail with the same set-up.


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## jsf (Aug 4, 2009)

I see. Really odd huh? hmmmm.


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## brice (Mar 10, 2010)

The only thing I can think of is that the image area is so large with so much detail that I'm getting it wet for too long. I'm using a 1500 PSI pressure washer. I've even tried a regular high pressure garden hose attachment. I'm going to reprint the image tomorrow am and try again. Shirts due by 7:00PM tomorrow. GULP. Been working on this a week...


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## tpitman (Jul 30, 2007)

You don't need a pressure washer to wash out stencils. If you do use one, make sure it's on fan spray. I usually just use regular water pressure with an old small shower head. I've done it with a pressure washer, but you've got to make sure it isn't a focused spray . . . more like a fog under pressure.


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## jsf (Aug 4, 2009)

I am using a diazo-type emulsion, so I am wondering your situation only happened when you changed your emulsion... Have you tried your old diazo emulsion?


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## brice (Mar 10, 2010)

It happens with both the garden hose and pressure washer. And it's only this design. 9.5 by 8.25, customer designed. Could it be the fact that it's taking too long to wash out?


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## brice (Mar 10, 2010)

After everything else you guys suggested and my own testing, I decided to start the morning fresh. I re-made the film positive. I even made a backup with the hearts and the words as separations.

The new film positive worked beautifully. It was the positive. It was the only variable from all of the other screens burned and washed out since Wednesday. With the new positive it burned and washed out beautifully. Can't say my heart *wasn't* in my throat as these 150 shirts are due by 5:00PM EDT. Actually it was probably on the floor with my stomach waiting to see what would happen. 

When else fails, redo the positive...


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## jsf (Aug 4, 2009)

brice said:


> After everything else you guys suggested and my own testing, I decided to start the morning fresh. I re-made the film positive. I even made a backup with the hearts and the words as separations.
> 
> The new film positive worked beautifully. It was the positive. It was the only variable from all of the other screens burned and washed out since Wednesday. With the new positive it burned and washed out beautifully. Can't say my heart *wasn't* in my throat as these 150 shirts are due by 5:00PM EDT. Actually it was probably on the floor with my stomach waiting to see what would happen.
> 
> When else fails, redo the positive...


Congrats then. . So what seems to be the problem with the first one? Not much black ink????


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## brice (Mar 10, 2010)

Can see no difference. They are visually equally opaque. Not sure what the problem was. All that matters is the replacement film worked.


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## brice (Mar 10, 2010)

Well, here it is 3 weeks later and I've finally finished testing and complete a few more jobs. I went to the ISS show in Orlando and Miami Ink supply gave me a pint of their white to try. At the time I didn't see that they had dropped a 21 step exposure strip in the bag with the ink. NICE!

I'm getting a solid 6 every time. Looks like I need to increase my exposure by 40% (multiply by 1.4 according to the step guide). I was using an autotype tester, but there was just too much detail to understand. I've been exposing for about 1:45 (this is down from 4:00-4:30 with a dual cure). I thought I'd be getting better times, but I never tested the dual cure and I suspect I was probably under exposing it too, but it was more forgiving. 

It's amazing the time having the proper tool (test strip) can save you.


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