Help me understand why my emulsion is locking up

[Homer]

Have you tried bypassing the tank and spraying emulsion remover on both sides and scrubbing it in then blasting it out with the pressure washer? That's the only thing I can think of to try at this point.

This is what we did when we had really tough screens, but we haven't tried it since we switched dip tank systems.

I'd love to see what the murakami and CCI reps think!

they will tell you to use murakami or CCI emulsion. which I would agree with.

[alan802]

We've also had screens locking up during reclaim the last few weeks.  I was reclaiming screens for a week before I went on vacation and that's how I noticed we were having issues and I haven't had a chance to really try to figure it out.  I'll tell you what I did when it was the worst:  I did the stacking method with 701 ink degradent and sprayed the 701, scrubbed, then did that till I have 5 screens stacked, then I washed out the ink with the pressure washer then put in the dip tank.  The 2 screens that had been sitting in the stack the longest both locked up completely and wouldn't reclaim and the other 3 were fairly hard to spray out.  I've concluded that if the 701 dries even just a little bit before you spray it with the pressure washer it will lock up the emulsion.  I did test a few screens to see if it was underexposure and the screens that haven't had any ink in them reclaim like a dream and those that were "de-inked" with screen opener reclaimed perfectly as well.  The screens that were de-inked with 701 locked up if there was any significant time between spraying/scrubbing and dip tank.  Looks like what John said earlier is what is happening here.  If you use a ton of 701 and get the ink completely out of the screen and do so quickly the screens reclaim just fine.  I thought I was having dip tank chem issues or underexposure, but that one test showed me it's working just fine.  I may have to switch to another ink degradent then use the 701 as a final step haze/ghost remover.

Is anyone else in a very hot environment that uses 701 and allows it to sit for any period of time having lockup issues? 

The few similarities between Eric and I are the heat and our overall method of reclaim.  It sounds like we're having the exact same issues because his description of his problems are to a tee what I was seeing yet we're using completely different dip tank brands and ink degradent.

[KevWilso]

Eric,

It doesn't sound like this is the culprit, but I thought I would throw it out there since no one has brought it up....  Once you pull the screens out of the dip tank are you rinsing immediately?  If emulsion remover has a chance to dry in the mesh before being rinsed off it can cause screens to lock up.

[ericheartsu]

Yep, they go from tank to washout sink.

At first i thought maybe we were neutralizing our tank by keeping the screens in there, but i don't think that's the issue

[mimosatexas]

My shop is hot as balls and I am not having this issue with HVP or SP1400.  I do not hit it with ink remover before the dip tank though, so that definitely could be the issue if Alan is seeing the same problem.  I think we use similar chems and emulsions etc, and we're both in Austin, so humidity and temp are the same.  The difference is I card off ink, dip and reclaim, then 701.

[Printficient]

Eric, I got tied up today.  Sorry.  I'll call you tomorrow for sure.

[IntegrityShirts]

Alan do you use one step? Aren't you both in  Texas? Maybe it's a bad/weak batch of reclaim Chem? I use kor-chem's dip tank fluid and it's honestly the best I have used yet. Are you guys covering your tanks when not in use?

[ericheartsu]

I'd say it's possible, but we just recently switched to easi strip, from cci-genzyme

[ericheartsu]

the more i sit with this, i don't think it's a chemistry issue. Unless the chemicals are so embedded into the mesh that, that is causing issues.

[KevWilso]

What do you use in your dip tank Eric?  Alan is using EW 701, and has EW 500 emulsion remover concentrate in his tank. 

I figure if you guys are using two different brands of chemistry we can some what rule that out.

[IntegrityShirts]

Has there been any nuclear bomb testing in TX recently?

But seriously, do you have a different emulsion laying around you can check against the Xenon?

[ABuffington]

Al from Murakami here.  Post exposing outside completes the cross linking process, usually about 10-20% of the emulsion needs more cross linking.  When it is underexposed, any solvent, be it mineral spirits, paint thinner, acetone or xylene will lock in the emulsion that is not cross linked.  The Acetone and Xylene can affect even a completely exposed screen due to hot solvents affecting the cross linking.  I haven't done testing with all the chems listed here.  In some cases there can be incompatible chemistry affecting exposed screens. For HVP, complete exposure followed by post exposure helps.  For SP-1400 once it is developed no more cross linking is possible.  Post exposing still helps dry SP-1400 and it also can be affected by hot solvents if you use them for wash up.

Billy from Easy Way once pointed out that you need to change your dip tank solutions periodically to prevent the emulsion remover in a dip tank from becoming so acidic that it hardens the screen instead of reclaiming it.  You can overload the dip tank with ER chemistry and create an acid that will harden the screens and make reclaim difficult.  I point out to my customers that the chems we have chosen for screen prep are compatible with our emulsions.  We have tested them against all of our emulsions for performance.  With the variety of chemistry out there I doubt any Chemical company has checked their chemistry against all emulsions for performance.  The process may be the same, but emulsions can vary in the amount of diazo and SBQ and other proprietary components may be affected.  Underexposed SBQ (HVP) screens washed with solvent cleaners or haze removers before reclaiming as well as old dip tank chemistry is usually the cause of difficult reclaiming.  As mentioned here, reclaim before de-haze if you are seeing lock in.  If still locking in go back to exposure times.  The maximum exposure time you can give a pure photopolymer and still hold detail along with post exposure helps a screen to be unaffected by the cleaning chems.

[CCI]

I've talked to Sonny about this for a long time. He suggested our dip tank chemicals got trashed, so we tossed our CCI genzyme, and switched to Easi Strip. it helped, but only for a week. now we are back at the same problem.


From this comment and your testing with screen 3A/3B it might be that you are killing the stripping chemicals in the tank. I would not recommend any solvents or cleaning chemicals go into that tank...if you are using them to remove ink I would rinse them off before the tank

Textile emulsions that are primarily designed for plastisol printing that have diazo added for discharge are prone to locking in with "hot" solvents. if you leave a strong ( hot) solvent on the type of emulsion for any length of time it will be difficult to reclaim or reclaim as a stringy sticky chunks rather than dissolving off the screen easily.
Underexposing will also cause reclaim issues but I don't believe that is the case here.

if you haven't already, try reclaiming without the tank with fresh stripping solution.

As someone else also pointed out, if you leave stripping solution on the screen to dry this will also cause the emulsion to lock in

[ericheartsu]

That's the thing though, we don't really leave any chemicals on the screen.

They come off the press, get ink carded off, sprayed down with HR-30, Sprayed off completly with water, on both sides. From here they either sit in the washout room, which is usually no longer than a weekend, then get dunked in the dip tank. They are pulled out from the dip tank, sprayed off with water, with a pressure washer, then sprayed with liquid renuit. It might sit for 10-15 mins with the renuit on, but it is sprayed off with water and the pressure washer quickly afterwords

[ericheartsu]

before we started using the supra easi strip in the dip tank, we used the cci genzyme stripper. We had a spray bottle full of easi strip that we'd use on our larger flatstock screens. Two seperate stripping solutions. When the genzyme started giving us issues, we started using the spray bottle of easi strip. It worked slightly better, and that's why we switched the dip tank over.

Also we just tried washing a screen that went right from the press with ink carded off, directly into the tank, and it took even longer to rinse out.