how long should I let my emulsion dry

3513 Views 3 Replies 2 Participants Last post by NoXid, Mar 7, 2018

Rcast

Discussion Starter · Mar 7, 2018

I am using HiFi Pink photopolymer emulsion and a drying cabinet set to 86 degrees. How long should I let my screens dry before burning image. also I was wondering the exposure time. I have a new 8 bulb vac exposure unit with digital timer.

I'm asking these questions because I use to use the Dual cure and like it but not the shelf life.

I did a test using 20 sec, 25 sec, 30 sec, 35 sec and 40 sec. the image washed out good for a bout 5 seconds the it all started to peel off and wash out.

screen was clean but I only let the screen dry for 4 hours in the drying cabinet. it use to be fine with dual cure.

what do I need to do to?

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NoXid

· #2 · Mar 7, 2018

Get a humidistat (about $10 at Home Depot), and put it in your drying box. You can then see how arid or humid it is in there after X amount of time. You want humidity under 50%, lower is better. I use a dehumidifier with my dry box and can get it down to into the 30s.

Once you are sure you've got a dry screen, do another step test. If the 40 sec in your first test was not over exposed, then start at like 60 and go up by 20. You can probably fit 8 increments on a screen easily enough.

Not going too heavy with the emulsion coat? A thick coat takes longer to dry all the way to the center of the emulsion layer.

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Rcast

Discussion Starter · #3 · Mar 7, 2018

I did a 2/2 coat. but usually do a 2/1. I live up in Steilacoom Wa and not sure of the humidity up here. but will definitely get a Humidistat to be sure. NoXid, do you use HiFi pink photopolymer? if so what exposure time do you range at with screens?

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NoXid

· #4 · Mar 7, 2018

Ah, yeah, well, your humidity there is going to be on the high side this time of year. I'm just a few hours south of you in Portland.

I've never used that particular emulsion, but I use Saati PHU, which is also a photopolymer, so probably pretty similar.

I used to do 2/1, but now do 1/1, sharp edge. Do whatever works for you.

I expose for 25 sec on 200 yellow mesh, with a 1000w metal halide unit ... so not directly comparable to your setup. Based on my past setups and what others have said, I would expect maybe around 2 minutes on a decent UV tube unit.

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