Screen Printing int dark

[jonse]

I understand that the emulsion used in creating a screen is light sensitive and should be used in the dark. However I recall reading somewhere that you can use some colored light bulb like yellow or blue or some something. I can't seem to find this info. does anyone know which color is safe?

[R.G.]

Screen printing emulsion is quite sensitive to UV and blue light. The lower the light energy, the lower the effect on the emulsion. However, it is much less sensitive than photographic emulsions.

It is common in wet-process photography (or was, back when that existed) to do a test exposure. You set up a test lamp, and a sensitive surface. You cover the sensitive surface, turn on the test lamp, and uncover the sensitive surface a little bit more at time intervals. Then you process the sensitive surface and you will see shades of exposure corresponding to the amount of light it got. This tells you how long you can work under that lamp before exposing things.

That being said, screen printing emulsion is dramatically less sensitive than photo emulsion. The standard exposure for screen emulsion is to give it something like 15 minutes in front of a high intensity arc-lamp. I suspect that a 60W incandescent bulb would not affect it for long periods of time. Just be sure to dry the coated screens in the full dark.

Even better, read the instructions on your emulsion can.   

[jonse]

Actually there is nothing written on the bottle of emulsion that came in the Speedball kit, and the instructions are not specific on this detail. From you suggestion I guess a very dim light in the far corner of the room shouldn't have an adverse effect. Just enough light to see what I am doing.

[R.G.]

I found the Speedball kit instructions on line here:

http://www.unprofessional.net/screen/Screen_PrintingInstructions.pdf

While it doesn't say what the maximum light is to NOT expose the stuff, it does say what the minimum time needed for proper exposure is 1 hour 32 minutes with a 150 W clear incandescent bulb 17 inches away from the dried screen. Light intensity is an inverse-cube relationship, so if you have a 100W incandescent bulb many times further away, exposure time should go up hugely, so one light bulb on the ceiling should be fine for hours, I'd guess.

[jonse]

Thanks R.G.
This is my first time attempting screen printing, and I'm a little weary of ruining it and having to start all over. But I guess that's the best way to learn.

Paul

[John Lyons]

Paul
The speedball emulsions are fine to work with in normal room lighting.
You only need 10 minutes or less to coat the screen and get it done.
When you finish making the screen then put it in a dark place to dry. A fan helps this go faster.

The lits usually come with two bottles, an emulsion and a sensitizer which may be liquid or a powder.
The instructions are crucial and so is a test run. It really depends on your set up and how you expose the image.

John

[The Tone God]

The inks those Speedball kits come with are not very good for enclosures in my experience. They are intended for things like cloth, i.e. T-shirts. Some inks are for paper too.

For enclosures you might want to look into enamel inks but handling those inks adds a new degree of complexity.

Andrew

[jonse]

The inks those Speedball kits come with are not very good for enclosures in my experience. They are intended for things like cloth, i.e. T-shirts. Some inks are for paper too.

For enclosures you might want to look into enamel inks but handling those inks adds a new degree of complexity.

Andrew

Yeah, I picked up a jar of acrylic paint as well. I'm not sure if it will do. I'm going to try it on a test enclosure first. If it doesn't work I guess I'll have to find some Nazdar paint specifically for preprinted metal.

Paul

[The Tone God]

Yeah, I picked up a jar of acrylic paint as well. I'm not sure if it will do. I'm going to try it on a test enclosure first. If it doesn't work I guess I'll have to find some Nazdar paint specifically for preprinted metal.

I tried the acrylic ink as well along with various additives. No dice. I think you will have to find an enamel ink like Nazdar. IIRC there have been some people around here who have used enamel inks with decent success. I never got around to trying out enamel ink with the Speedball kit so I cannot comment further on that aspect.

Andrew