Screen Printing Forum

I just switched to QTX emulsion from an Autotype product and I am having problems.

When washing out after exposing the design looks like it has no emulsion left where exposure was blocked by my film but when I try to push ink through it there are some spots that have a clear film that blocks the ink. During washout these clear blocked areas are not visible when wet and look just like the areas that have correctly washed out.

What is causing this?

How can I prevent it?

Is there a way to remove the blockage on press without damaging the rest of the screen?

I don't use QTX but have in the past You may need to adjust your exposure time, because not exposing the entire deposit of emulsion allows a run off of unexposed emulsion that can clog your OPEN areas of your screen. Usually a damp cloth will fix the problem at press, or using an air hose to blow off any excess water before you set your screen to dry.

AH HA

That makes sense.

Thanks for the advise!

I have used QTX and was very please with it. What type of light source are you using? I found out that this is a very fast in exposing. I had to burn a few screens to get a handle on this. This QTX is kinda tricky if you under expose your screen the top layer will be very slimy and looks like it just washes off the screen. If you over expose the screen it will be very hard to clean out the stecil part. As the other person stated also blot the screen with a paper towel that will take the loose stuff out of the stecil area.

leapfrogz wrote:I have used QTX and was very please with it. What type of light source are you using? I found out that this is a very fast in exposing. I had to burn a few screens to get a handle on this. This QTX is kinda tricky if you under expose your screen the top layer will be very slimy and looks like it just washes off the screen. If you over expose the screen it will be very hard to clean out the stecil part. As the other person stated also blot the screen with a paper towel that will take the loose stuff out of the stecil area.

Thanks!

I am redoing my step tests to make sure my times are right. I think I have been underexposing. I have been able to make usable screens since blotting but I still think I need to burn longer.

I did a step test when I first switched but i was in a hurry.

This time I will do it right for each mesh count with screens coated at the same time.

I am using 1/1 coat method with the sharp edge of the coater.

My exposure unit is a Point 1K from WorkHorse and my times have been

1:55 - 305 Mesh
2:25 - 230 Mesh
2:50 - 156 Mesh
3:15 - 110 Mesh

I think my new step test will make those a little longer.

Your problem is called scumming. At least that's what I've called it for the last 25 years. It is caused by emulsion not being totally washed out after exposure. Leftover emulsion flows into open areas and dries. You can see it at an angle under light.Try washing out a little more and dry as quick as possible. A simple box fan or sunshine on a good day will do. I still get it sometimes myself. It can help to lay screens horizontal to dry instead of leaned against the nearest table leg or wall as well. If scumming is in a large open area you can moisten a q-tip with stencil remover and blot quickly. Doesn't work all the time, but most times scumming isn't very severe and can be removed with a little persistence. Best bet is spending a little more time in the washout phase. If you like QTX maybe try RLX sometime if it fits your needs. I print textiles and flat stock and use RLX for both. Plastisol and solvent ink work well with it. You can get it in clear with the dye seperate so you can adjust the tint of your emulsion to help with registration issues. Hope this helps.

Thanks for the info!

I upped my exposure times, spent more time rinsing the ink side and quickly blot both sides with paper towel making sure not to rub across and have not had any scumming problems since. I think the longer exposure time are what really did the trick as I am not leaving a film of unexposed emulsion on the ink side. That was what was running back into my open mesh before.

I really like QTX. It is much better for me that the AutoType I was using before. Much faster exposure times and much easier emulsion removal after printing.

I will look into the RLX too. Thanks

KIWO Poly-Plus S Dual Cure Emulsion.....QTX gummy clogs the pipes after a while.