Issue with exposing all the sudden

Here you can discuss issues related to exposing screens for screen printing. This includes determining the exposure, light sources and washing out the stencil in the washout booth. Emulsion issues may also be addressed here.

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Ochtees
Senior Screen Printer
Posts: 70
Joined: Sat Apr 21, 2012 4:59 pm
Contact:

Issue with exposing all the sudden

Post by Ochtees »

So yeah, I have been printing for about 2 years now. All the sudden I am having major issues w/my exposures and them washing out.

Here is what I am doing and my issue. I am coating the screen once on the back, once on the front, letting it dry for a day then coating it on the back one more time. I let that dry for 2 days. I then line up my stencil and burn it for 6.5 minutes. When I wash it out the front side (where the ink goes) turns milky and yellow and seems to wash off. Then it starts to blow out. Lately it has started to look very cracky. Oh another note, I just bought NEW emulsion too, so this is brand new emulsion.

I have tried placing a dehumidifier in the room to help dry it out.
I have tried exposing for 7, 8 and 9 minutes thinking its not fully getting exposed
I am using a 110 mesh screen
I'm suing ProChem DXP Pink emulsion

Here are some pictures

My Emulsion:
Image

The back of my problem screen:
Image

The front of my problem screen:
Image

Any ideas? what I am going to do now is go back to a 1/1 coat and try a 150 screen burned back at 6.5 mins. My original
Cody Ochsenbine
Custom & Blank T-Shirts
Saati
Instructor
Posts: 82
Joined: Thu Mar 22, 2012 10:02 am

Re: Issue with exposing all the sudden

Post by Saati »

I want to clarify something. You are having the same issue with the old bucket and the new bucket of emulsion (right)?

if so then I would not be looking to the emulsion as the culprit. Intead I would look at the exposure unit. What type is it?

With the way the stencil looks it appears underexposed.....
Underexposed screens are from the following reasons (typically)
Exposure time too short
Coating thicker than normal
Exposure lamp not putting out enough UV light (still lights up with white light but not UV)
Extremely high humidity and screens are not dry
Emulsion is not correctly sensitized (either not enough sensitizer in the bottle or sensitizer left int he bottle after mixing)
Ochtees
Senior Screen Printer
Posts: 70
Joined: Sat Apr 21, 2012 4:59 pm
Contact:

Re: Issue with exposing all the sudden

Post by Ochtees »

So i got my issue resolved. I called the creator of the emulsion. I was coating my screen wrong. I was coating the PRINT side twice, and not the ink side twice. Also I would coat both sides, wait a day, and coat the print side again. That was TOTALLY wrong. They said if I wanted to double up on a side that you do it the SAME TIME you do both sides. Also they said there is really no reason to do a 2 hit. So I stopped that all together, I now do both sides, and let it dry. I also bought a DEHUMIDIFIER which helped dry it A LOT!
Cody Ochsenbine
Custom & Blank T-Shirts
Saati
Instructor
Posts: 82
Joined: Thu Mar 22, 2012 10:02 am

Re: Issue with exposing all the sudden

Post by Saati »

It is amazing what a good drying chamber will do as well as having a dehumidifier. Glad you got it under controll.
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