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Gmen · July 24th, 2007

Hi! the usual new to screen printing... But I have printed a few jobs here and there but now I'm not able to unmask my screens and I'm wondering is it my emulsion is it my water pressure or is it my exposure. I'm using a 500w halogen for my exposure, my emulsion is saatichem graphic DS, and im using a water pressure gun. The problem I get is that my emulsion gets wet when trying to unmask just leave at about the same time as my masked area...

Could Someone Please Help Me!

Squirts · July 24th, 2007

Quote:

Originally Posted by Gmen


	Hi! the usual new to screen printing... But I have printed a few jobs here and there but now I'm not able to unmask my screens and I'm wondering is it my emulsion is it my water pressure or is it my exposure. I'm using a 500w halogen for my exposure, my emulsion is saatichem graphic DS, and im using a water pressure gun. The problem I get is that my emulsion gets wet when trying to unmask just leave at about the same time as my masked area... Could Someone Please Help Me!

First impression is that you have a film problem (Not Opaque enough) a quick way to see if this might be the problem is to put something you know is 100% solid somewhere on your next screen an see if it washes out Ok when the rest doesn't .... a piece of Black Tape on a business card will do... just cut a small piece of it, and lay it somewhere away from your artwork on your next screen....

Gmen · July 24th, 2007

I don't think this would be the problem since im able to unmask some of my decal areas. But I'm still going to give it a shot... I'm so desparate to figure it out!

Thanks

RichardGreaves · July 24th, 2007

Quote:

Originally Posted by Gmen


	I don't think this would be the problem since im able to unmask some of my decal areas.

Help me to understand. What do you mean by unmask? - and decal areas?

"emulsion gets wet when trying to unmask just leave at about the same time as my masked area" ?

This is probably a simple language problem.
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Saatichem Grafic DS is a solvent resistant diazo sensitized emulsion. Using a 500w quartz halogen for exposure, would probably take more than 10 minutes to expose.

Properly exposed, any un-exposed stencil should dissolve with simple city water pressure and shouldn't require a pressure gun.

If the whole stencil washes out, it wasn't exposed enough.

Exposure and washout are easy functions. If it dissolves and goes down the drain - it wasn't exposed. This is why I suggest taping a dime to the stencil as a benchmark of absolute opacity and the area it covers will always dissolve easily - Unless it was contaminated with heat or UV light in storage.

If it doesn't wash out, it was crosslinked with UV-A light or heat.

If the whole stencil resists dissolving (even under the dime), the stencil was exposed in storage.

If the whole stencil washes out, it wasn't exposed enough.

If areas that are covered by the positive don't wash out, UV-A light leaked through and your positive failed. This is why it is so helpful when there are problems to use a dime to test for UV light contamination.

Gmen · July 25th, 2007

I have nothing to mesure my exposure time where could i get those?
Unmask decal area = remove the emulsion in my stencil

Normally I expose for 15minutes... I just tried exposing 8 minutes with a film and a full opaque business cards to see if my film was the problem. And I was able to remove my stencil from the film and the business card easely. I'm going to try a couple more just to make sure. But I still would love to know where could i get something to calculate my exposing time...

Thank You