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emulsion and exposure question

2629 Views 8 Replies 5 Participants Last post by  kenirob
Hey everyone so I'm using rxp rayonet dual cure and 500 watt halogen. I've done 3 step wedge tests and got exposure time to 3 minutes. Now the images washes out good but the emulsion on the screen is washing away quite a bit. The screen was coated 2 times on print side and 1 time on squeegee side. It's a yellow mesh 250. I'm exposuring 18-20" away. 3 minutes seems pretty fast but this emulsion suppost to be very forgivingjust wasn't expecting emulsion to. Be super slimey its almost a race to spray the screen to wash out the image before all the emulsion washes off the screen.
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You should look around craigslist or other classifieds and find a yudu. I had lots of problems when i first started usung the work light. All problems were resolved when i found someone selling the yudu for cheap, it makes a great exposure unit.

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Sounds like you're not drying your emulsion thoroughly before exposing.
I dry mine for 24 hrs before use.
Slimy can also be from under exposure, but since you say that you're getting a good exposure, I'm staying with the drying screen (before exposure) aspect.
Hey everyone so I'm using rxp rayonet dual cure and 500 watt halogen. I've done 3 step wedge tests and got exposure time to 3 minutes. Now the images washes out good but the emulsion on the screen is washing away quite a bit. The screen was coated 2 times on print side and 1 time on squeegee side. It's a yellow mesh 250. I'm exposuring 18-20" away. 3 minutes seems pretty fast but this emulsion suppost to be very forgivingjust wasn't expecting emulsion to. Be super slimey its almost a race to spray the screen to wash out the image before all the emulsion washes off the screen.
You are way under exposing. Your exposure time should be around 7-13 min. I have used that emulsion and a 500W light to expose.

Sorry not trying to start any arguments but the Yudo uses a standard light bulb and is a bad idea. 16"-18" is a good distance for a halogen. 2nd no matter how long you dry without proper humidity control. I can dry a screen in 30 min as I dry with 35% humidity and air circulation. I normally will still wait 2 hrs or until humidity gauge is at 40% in the dry box.
Sean's right, way underexposed. The emulsion is not hardening enough to withstand the washout.
You are way under exposing. Your exposure time should be around 7-13 min. I have used that emulsion and a 500W light to expose.

Sorry not trying to start any arguments but the Yudo uses a standard light bulb and is a bad idea. 16"-18" is a good distance for a halogen. 2nd no matter how long you dry without proper humidity control. I can dry a screen in 30 min as I dry with 35% humidity and air circulation. I normally will still wait 2 hrs or until humidity gauge is at 40% in the dry box.
No offense taken! LOL! I just had all kinds of problems trying to use a work light and had to re-do several screens before I could get it right & when I started using the yudu to expose I never had to re do them every screen I ever burned with it came out perfect. I was a noob with the work light & the yudu just took the guess work of how far to have the light away & how long so it made things easier for me. BTW I wonder if you could sub the lights in a yudu with black lights, I guess that's another discussion.
Thanks guys. The emulsion dryed for 24 hours in basement 60-70 degrees. I've done several test step wedge tests that puts exposure at 3 minutes. The test was 1-14 minutes then a 1-8 minute both put it at 3 minutes. I then exposed the entire test film for a solid 3 minutes. Image washed out nice and emulsion became super slimy. So I'm confused the first 2 tests emulsion hung in there a the 3 minutes only exposure was running slimy. Emulsion was in dry basement 60 70 degrees was for sure dryed 100%. So if underexposed why is the step test awesome at 3 but emulsion can't handle the wash out?
Are you giving the emulsion after exposure and developing time(wetting the screen and letting sit for a min). If your just washing out with no developing time then that why your under exposing. Ryonet help center has some approximate times with that emulsion and the 500w.

I can tell you that if its slimy its under exposed. I can also tell you you exposing your dual cure less time then I was exposing photopolymer emulsion with a 1000w halogen witch is a faster exposing emulsion. With a unfiltered black light unit I was exposing that same emulsion at 5-7 min which has much more usable UV then a 500w halogen.

I last thing to check is the humidity in your basement. If its 50% or higher it possibility your emulsion is not drying thoroughly. It maybe dry to the touch but without the cs,reen humidity dropping below 50% the will not be 100% dry. This will also cause slimy emulsion.
hi everyone thanks for your input. I've changed the exposure lamp setup from facing up into the glass/screen to lamp exposing downwards on the screen. The heat rising up from the 500w halogen had an effect on the exposure time without a doubt. So I exposed the screen in 12 minutes no issues.
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