Been screenprinting on glass and plex for several decades and have encountered most of the usual problems regarding photo emulsions such as exposure times, vacuum tables, transparencies, timing, shelf life, etc. Today I discovered another problem. Using TZ emulsion and applied as usual. For small jobs I simply use plate glass to provide proper contact during exposure. The emulsion worked fine yesterday but today I discovered that after exposure it appeared over exposed (open areas were not open). When looking at all the variables the only difference was that I used three very thin sheets of 8x10 taped together to provide contact with the transparencies since my usual plate glass was not handy. When switching back to plate glass, no problem. This is not a huge problem as I continue to work with the plate glass and have a 99% success rate but I am very curious if the three glass sheets, in some manner, affected the exposure. Thanks for your input.
Bob
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This is an interactive Bulletin Board on the topics of Sign making, design, fabrication, History, old Books and of coarse Letterheads, Keepers of the craft. The Hand Lettering Forum features links to resources, sign art history, techniques, and artists profiles. Learn more about Letterheads at https://theletterheads.com. Below you'll see Mchat has been added as a live communication portal for trial, and the Main forum Links are listed below.
Screenprint exposure
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Robert Schwieger
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Patrick Mackle
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Re: Screenprint exposure
I have a simple idea as to what caused your "over exposed" appearing image.
With one solid glass pane, the the light particles enter and pass through relatively undisturbed from the light source.
However, passing the same light source particles through stacked glass disrupts and diffuses their straight projection.
They have to deal with added surfaces of micron dirt and dust, moray lines (contact rainbows) and the fact the the plates are not in absolute optical contact.
Actually adding an "optic jell" between the plates would probably fix the problem, maybe not for a space telescope but surely good enough for screen emulsion.
Another thing is if you look really close at sheet glass from the edge, it looks like apple juice in a glass with swirling waves of unemulsified ingredients.
You see them because they are bending reflected light. Now imagine 3 separate layers of glass causing all these problems and that explains the fuzzy edges on your image.
Check this: If I print an acetate out of my laser jet printer to use as a film to burn a screen. I must burn it with the toner directly in contact with the emulsion.
If I try to burn it with the toner on the opposite side, the light molecules will bend as the pass round the thin layer of toner particles, move freely through the acetate layer and expose the emulsion under the toner image, just enough to leave a residue the can't be cleared easily. Of course this problem can easily be cured by spraying the toner side with a light coat of KRYLON clear coat which swells the PVC toner particles and seals them together.
Pat
With one solid glass pane, the the light particles enter and pass through relatively undisturbed from the light source.
However, passing the same light source particles through stacked glass disrupts and diffuses their straight projection.
They have to deal with added surfaces of micron dirt and dust, moray lines (contact rainbows) and the fact the the plates are not in absolute optical contact.
Actually adding an "optic jell" between the plates would probably fix the problem, maybe not for a space telescope but surely good enough for screen emulsion.
Another thing is if you look really close at sheet glass from the edge, it looks like apple juice in a glass with swirling waves of unemulsified ingredients.
You see them because they are bending reflected light. Now imagine 3 separate layers of glass causing all these problems and that explains the fuzzy edges on your image.
Check this: If I print an acetate out of my laser jet printer to use as a film to burn a screen. I must burn it with the toner directly in contact with the emulsion.
If I try to burn it with the toner on the opposite side, the light molecules will bend as the pass round the thin layer of toner particles, move freely through the acetate layer and expose the emulsion under the toner image, just enough to leave a residue the can't be cleared easily. Of course this problem can easily be cured by spraying the toner side with a light coat of KRYLON clear coat which swells the PVC toner particles and seals them together.
Pat
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Mark Summers
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Re: Screenprint exposure
I'm curious about the emulsion idea. I'm am familiar with emulsion
and all but I'm not sure why you would need to go that route.
As I recall emulsion needs chemicals for the washout. The
emulsion idea seems somewhat laborious for my needs.
I have been using Chromaline Reflex. It is a exposure film that washes
out with water. That's it. But most of the time I use Ulono-Cut green.
Cut it out on your plotter. This method is really effortless.
Don't know if this is exactly what you wanted to hear but my thoughts.
Mark
and all but I'm not sure why you would need to go that route.
As I recall emulsion needs chemicals for the washout. The
emulsion idea seems somewhat laborious for my needs.
I have been using Chromaline Reflex. It is a exposure film that washes
out with water. That's it. But most of the time I use Ulono-Cut green.
Cut it out on your plotter. This method is really effortless.
Don't know if this is exactly what you wanted to hear but my thoughts.
Mark
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Danny Baronian
- Site Admin
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Re: Screenprint exposure
Mark,
Images with fine detail cannot be cut with a vinyl cutter, the only option would be using a film positive and photo emulsion. Imagine a customer requiring the image of the Trans America building in SF, or the Empire State building, screen printed or etched onto a 8" x 8" glass square. The building would be 6" high, the hundreds of windows thousandths of an inch wide, or a R&E reproduction that has scrolls with lines 1/16" or less.
Only way to do either one would be with photo emulsion, and would be the only cost effective way to produce a fine, detailed image.
Look at images on the forum, most require a film positive and photo emulsion to reproduce that type of detail. Some examples posted are done by hand, but not all. Check out Pat Mackles web site and photos from Dave Smith posts.
As far as chemicals, you can buy photo emulsion pre mixed, adding the sensitizer when mixing for the first time. The emulsion is applied to the screen, exposed and washed out with water. There is also pre sensitized sheets that can be applied to the screen. With either method you're still using some of the same chemicals: haze remover and stipper (enzimes) to reclaim the screens, solvents to clean up.
It would be nice to eliminate photo emulsions, but films like Ulano Cut has limitations.
Danny
Images with fine detail cannot be cut with a vinyl cutter, the only option would be using a film positive and photo emulsion. Imagine a customer requiring the image of the Trans America building in SF, or the Empire State building, screen printed or etched onto a 8" x 8" glass square. The building would be 6" high, the hundreds of windows thousandths of an inch wide, or a R&E reproduction that has scrolls with lines 1/16" or less.
Only way to do either one would be with photo emulsion, and would be the only cost effective way to produce a fine, detailed image.
Look at images on the forum, most require a film positive and photo emulsion to reproduce that type of detail. Some examples posted are done by hand, but not all. Check out Pat Mackles web site and photos from Dave Smith posts.
As far as chemicals, you can buy photo emulsion pre mixed, adding the sensitizer when mixing for the first time. The emulsion is applied to the screen, exposed and washed out with water. There is also pre sensitized sheets that can be applied to the screen. With either method you're still using some of the same chemicals: haze remover and stipper (enzimes) to reclaim the screens, solvents to clean up.
It would be nice to eliminate photo emulsions, but films like Ulano Cut has limitations.
Danny
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