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screen printing => Screen Making => Topic started by: noortrd on January 23, 2014, 10:47:50 AM
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Any body checked hxt ? Why some emulsion fast and some slow?
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There are countless ways to "build" an emulsion but primarily the difference is Diazo (slower) and Photopolymer (faster)
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Any body checked hxt ? Why some emulsion fast and some slow?
I found this thread and I know there had been a few others that noortrd started reguarding HXT emulsion, and since a while back, I brought the HXT to this forum, I feel responsible to respond. First sorry for replying so late, I hadn't been participating on the forum for a while. My wife and I were standing by my father in law's side for 8 months while he was battling stage 4 lung cancer that eventually spread through out his body and eventually shut him down a few weeks ago. With all that going on, I really didn't have a lot of time to be on forums, and I'm sure folks can understand what's more important. Ok back to this emulsion.
noortrd, I sent you a "highly detailed" PM through the forum a few months back when the topic first came up about HXT emulsion containing all of the steps that we developed using this emulsion for water based printing. Everything anyone would need to know about it would be in that message, if you didn't see it, check your inbox, I can always re-forward it to you. But for the sake of interested parties, YES we still use HXT by CCI for our "waterbased and discharge printing". It's totally awesome and I stand by it. From what I have read from guys trying it and not having success, the bottom line is that you , "can NOT rush the exposure". Just because you don't feel a slimy inside does not mean that the emulsion has reached it's full cross linking and like any other unexposed emulsion, will break down. You have to find your time with your set up. We coat 2 over 2, round edge, we image with a CTS, so when exposing, no glass, no film, "take this into consideration for your exposure time". We make sure screen room, putting the meter on a screen frame to check the humidity right up close, that we are below 40%. We try and get our room to 30%, but it's hard in central FL. Believe me, how dry the emulsion is before exposure seriously affects your outcome, again, do not rush it. Once we expose, we are using a 3k trilight, again, no glass, no film, for us, 400-500 light units, which can vary between 5-7 minutes. Depending on your exposure set up, and if you are still using film and glass, you may need to be up higher, unless you have a more powerful unit than the 3k we use. Ok, I understand, that seems like a long exposure time. Consider this. If you do it right ONCE, you can eventually be confident to go to press using no diazo, no hardeners for discharge prints, and even wet on wet discharge prints for at least 3,000 strokes. We've pushed it beyond a few times, but I'm keeping that number conservative. If you rush your exposure, you will break down. If you try to expose the emulsion where it's got a humidity level higher than 40% and don't seriously compensate your exposure settings, it will break down. If you want to use this emulsion just follow the steps. Trust me when I say I've tried all the others everyone is using, and even though had success with a few of them, the fact that we had to use diazo, which isn't the worst thing, but think about it, adding diazo, you just added water to an already thinner emulsion, going to have an affect. Not to mention, then going through the exposure process, ok, maybe half the time, but then you are spraying hardener, which has it's own draw backs, not to mention the wasted time reclaiming that hardened screen. If you do it right with HXT, you can have an emulsion, "for water based printing", that coats easy, and can take you to press with confidently, But, you have to do it right, and "NOT RUSH IT!!!!!". If you want to expose screens in 1 minute ect for WB printing, don't expect HXT to work for you, neither would Nova by Xenon, which if wasn't 100 bucks a gal, would be my other choice emulsion for water based printing. I hope this sets some things clear, and I apologize if anything felt I brought a product to the board and then disappeared, but I'm sure anyone can understand what's more important in life, typing on a forum or being there for your family. Bottom line though, you always have to find what product fits your way of doing things best, that's what we try to do.
Mike
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Diazo emulsion breaks down faster (becomes more unstable) once it is mixed. However, it gives better halftone details over the photopolymer.
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its difficult to maintain this type of atmosphere in pakistan.
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its difficult to maintain this type of atmosphere in pakistan.
I can only imagine, It's tough here in central Fl as well. Running 2 dehumidifiers to try and stay below 40% humidity and it's a constant fight, door opens a few times and it's right back up above 50%.
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A few weeks ago I took a screen coated with Chromablue to the press for a 144 piece white DC run. I cooked the crap out of the screen and blocked it out, exposed it again for a long time, then put hardener on it, basically treated it like the HVP on a normal DC run, and it held up perfectly fine. It held up better than some of the HVP screens and some of the other emulsions I've tried for DC printing.
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A few weeks ago I took a screen coated with Chromablue to the press for a 144 piece white DC run. I cooked the crap out of the screen and blocked it out, exposed it again for a long time, then put hardener on it, basically treated it like the HVP on a normal DC run, and it held up perfectly fine. It held up better than some of the HVP screens and some of the other emulsions I've tried for DC printing.
It's not all in the prep, but a lot is in the prep. I bet most emulsions, whether they claim water resistance or not, when prepped correctly would hold up pretty well. In any case, you've got to cook 'em at every step- after coating, after expo, after hardening.
We have the opposite problem from most, seems to be a bit too dry here. Might need to look at moving air v. dehumidifying or get a more controlled dehumidifier. Looking first for an emulsion that doesn't mind getting cooked out and dried out really well. Nova's got that down pretty well. Still searching.