TSB
screen printing => Ink and Chemicals => Topic started by: ericheartsu on August 22, 2014, 07:59:18 PM
-
Emulsion: Xenon Nova (dual cure, with diazo)
Chemistry: CCI HR-30 for plastisol, CCI eco wash for waterbased/discharge inks
Dip Tank: Easiway Easi-strip (in the past we used cci genzyme)
We keep getting locked up screens when we are reclaiming them, and we cannot figure out why!
Our screens are kept around 30ns, we are using shur loc and new man panels. Plastisol is never left on screens longer than a day, and waterbased is washed out immediately.
We have light staining on our mesh, but it's taking about 20 mins to spray out a screen, even after soaking in a dip tank for 5 mins.
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.
CCI suggested that it could be the HR-30 that we use to reclaim our plastisol screens, which it might be. I believe it's a solvent based cleaner, and it's possible this emulsion is not solvent resistant.
I have my guy trying some screens with citra paste as I type this! so hopefully that's the cure all, but this is our second wind of a busy season, and we are washing out about 30 screens a day. So any suggestions would be awesome!
-
In the old days, we actually hardened some emulsions by wiping with our cleaner, Xylene.
Underexposed screens are even more susceptible to this effect.
-
I would also take a look at my emulsion curing area and recheck my exposures..
Heat is what locks emulsion, mainly the ones that did not properly crosslink..
-
this sounds like under exposure and or you are using the stain remover before reclaim.
check for proper exposure
reclaim the screen first, then use the stain remover and final degrease step at the end.
-
i'm going to check our exposure this weekend, but we had it pretty dialed in with the i-image. at least i thought we did.
And typically we'll clean off all the ink, put in the dip tank, spray with liquid renuit, then degrease if needed
-
reading the description of the CCI HR-30, it says it can be used as a haze remover. I would toss a bet that this is the culprit and it may be killing your tank fluid.
-
Aerosols like screen opener or mineral spirits used on press to clean an image area will harden emulsion making it difficult to remove in reclaim. Take note how the emulsion comes out of the screen, areas that have been cleaned with one of these products will come out in stringy sheets, the unaffected area should just wash out.
Killing the tank is one reason we go straight from press to the dip tank, adding another chemical to the tank could kill it. If you do want to remove the ink before hand make sure the remover is compatible.
-
i'm going to check our exposure this weekend, but we had it pretty dialed in with the i-image. at least i thought we did.
And typically we'll clean off all the ink, put in the dip tank, spray with liquid renuit, then degrease if needed
Liquid Renuit functions as a degreaser (though expensive if used for only that, LOL!)
All symptoms seem to lead back to a possible combination of a solvent ink cleaner and underexposure, and possibly the emulsion itself, as when I used Nova one part, it reclaimed more like bubble gum than actually dissolving.
-
have you tested exposing a screen and putting it directly in the tank? no ink or cleaning before dipping. That would narrow down the issue. You could also clean little areas with different chems on a single screen and see if any areas are harder to remove post dip.
-
have you tested exposing a screen and putting it directly in the tank? no ink or cleaning before dipping. That would narrow down the issue. You could also clean little areas with different chems on a single screen and see if any areas are harder to remove post dip.
The only way this would narrow down the issue would be a brand new screen. One that hasn't had any chemical on it. I am doing some r&d at a shop here in town that uses Nova the way Eric does. I am trying to replicate the issue. I'll post results. On a side note Nova is a photopolymer not a dual cure. The diazo is added to make the stencil hold up to WB Discharge ink with no added steps. Eric call me today and let me know the parameters you are doing.
-
have you tested exposing a screen and putting it directly in the tank? no ink or cleaning before dipping. That would narrow down the issue. You could also clean little areas with different chems on a single screen and see if any areas are harder to remove post dip.
The only way this would narrow down the issue would be a brand new screen. One that hasn't had any chemical on it. I am doing some r&d at a shop here in town that uses Nova the way Eric does. I am trying to replicate the issue. I'll post results. On a side note Nova is a photopolymer not a dual cure. The diazo is added to make the stencil hold up to WB Discharge ink with no added steps. Eric call me today and let me know the parameters you are doing.
Sonny, do you, or others, see the Nova bubblegum effect I mentioned? (btw, I don't dip)
-
Sonny thanks for the info! sorry I posted it wrong! I'll call you on Monday!
Andy we've only ever gotten the stringy effect when it's been bad emulsion. Typically it just washes off, but it comes off in layers. For instance the ink side of the screen typically comes out with a single spray of our pressure washer, but the garment side takes several short blasts over and over again to really get it off.
-
Also we tried some citra paste yesterday, and it didn't really seem to help.
Another thing we do, once screens are exposed they sit out in the sun to post expose. Sometimes for 15 mins, sometimes for 4 hours. Would it be hardening the emulsion to much that it can't strip down?
-
Also we tried some citra paste yesterday, and it didn't really seem to help.
Another thing we do, once screens are exposed they sit out in the sun to post expose. Sometimes for 15 mins, sometimes for 4 hours. Would it be hardening the emulsion to much that it can't strip down?
We do this... Probably not 4 hours.
Cross linked is cross linked I would think... At least when it comes to straight emulsion and exposure.
-
when we coat our screens, we do 1/1 on the sharp side. I do the garment side first, then flip it and start from the bottom on the ink side.
Thats the correct way to do it right?
When we wash our screens out they aren't slimey on the ink side at all. They wash out with no issues at all
-
To someone who really knows: does this "post" exposure still have any efficacy on photopolymer emulsions with Diazo added?
I know that it doesn't on straight Diazo emulsions.
-
We use different methods depending on mesh or the eom we are striving for.
-
when we coat our screens, we do 1/1 on the sharp side. I do the garment side first, then flip it and start from the bottom on the ink side.
Thats the correct way to do it right?
When we wash our screens out they aren't slimey on the ink side at all. They wash out with no issues at all
I'd guess you aren't underexposing based on the minimal amount of emulsion that you're applying, and the fact that your screens aren't scumming. I coat the majority of our screens 2/1 using the round side of the coater, but initially used the glisten method to reach that number.
From your description I'd wager its a dip tank chemistry issue. Do you have any manual reclaimer around that you could try out and see if it has a different effect on the screens? Grab a quart of Strip-E-Doo or whatever your local supplier carries and give that a shot. If it works, you know the problem is the tank. If not, its the screens.
The only other thing that comes to mind is if you are letting your screens sit too long between the dip tank and reclaim. If they are allowed to begin drying with the dip tank chemical still on them, they can quickly become almost impossible to reclaim.
-
From what I'm reading this doesnt sound like a dip tank issue, or at least you havent done the tests necessary to determine if that is the problem based on what I'm reading in this thread.
I would test a coated and exposed screen with no stencil and no ink or ink remover having touched it. If the dip tank reclaims the emulsion after exposure just fine, the issue is not the tank. If it doesnt, you know it is the tank.
If it isnt the tank, try exposing but not post exposing in the sun like you have for one screen, then try one with the post exposure outside. Again, no ink or chems, just emulsion and exposure. If again they both reclaim fine, you know it is not the post exposure.
Now the possible issues are the ink remover, or possibly the emulsion getting too hot on your press due to flashed pallets (i only say this because you said the ink side reclaimed easier). I would try a screen where you havent touched it with ink, but rub the remover on only half. If that side locks up, you know its the remover. If it doesn't, it is likely heat. You might test this by taping something to the bottom on half of a screen where you are doing a pocket print to block some of the heat from pallets touching the emulsion, or if you have a quarts flash that can flash only one area, try that. An easier way to test would probably be to just do a short run and a long run on screens that have been prepared and treated the same throughout their cycle and see if the longer run screen is harder to reclaim.
I just don't think it is at all obvious that this would be a dip tank issue without the above tests.
-
WHat kind of exposure unit do you use?
-
WHat kind of exposure unit do you use?
we were using a richmond soalr bearm 7k, but now use an I-image STE II
-
We use different methods depending on mesh or the eom we are striving for.
We do as well, but i was just posting our general method, as for the most part 99% of our screens are coated this way. Previously we were coating 1/1 sharp for discharge only screens, 1/0 round for plastisol only screens.
We switched from this method as we were using higher and higher mesh in our discharge and waterbased printing
-
Testing Trial round 1
I took 4 screens. All 166 mesh screens and did the following tests:
Screen 1: I set this sucker outside in direct sunlight for roughly 30 mins.
Screen 2: No exposure, just straight in the dip tank
screen 3A: Top part of the screen, printed the M&R clarity test, exposed on the STE II for 12 seconds
Screen 3B: Bottom part of the screen, printed the M&R clarity test, exposed on the STE II for 24 seconds
First thing i did was washout screen 2, washed out in 5 seconds, no issues what so ever.
Second thing i did, after Screen 3 was exposed, i put this in our water tank. Then i took this screen out and rinsed it. The top portion of this screen (which was exposed for 12 seconds), rinsed out almost perfectly to the naked eye. The bottom part was Very over exposed to the point where nothing washed off. The next thing i did was take Screen 3, and spray HR-30 on the bottom portion of this screen (the part that was overexposed), inside and out. Next i brought it to the dip tank, and let it sit for a minute. Now in hindsight I feel like i didn't let sit long enough, but here is what i found. Both the top and bottom were more difficult to wash out. In fact the over exposed portion with the Hr-30 was actually easier to reclaim than the top portion that was exposed correctly.
Last thing i did was put Screen 1 in the dip tank, and let it sit for a minute. Same thing, should have let it soak a bit longer. Took it out, saw it wasn't reclaiming very easily, so I put it back in and let it soak for 3-4 minutes. From there it washed out easier, but still need to put some time in spraying it out.
So i think i've concluded so far, it isn't the dip tank chemistry. I don't think it's the Hr-30, but I am open to the possibility that in this test, everything was done quicker than it would be in real life reclaim). are my screens being overexposed? Even with my halftone images, we expose at 11 seconds, any less and we can see it being underexposed. Anymore and we lose dot detail.
-
Eric quick question. What amount of heat if any are your screens exposed to. Any type of heat (wet or dry)
-
Eric quick question. What amount of heat if any are your screens exposed to. Any type of heat (wet or dry)
well, our shop is in houston, so it's usually pretty humid, and air flow is something we are working on in the shop.
In the dark room, it can range from 75-85 degrees throughout the day, usually no more than 40% humidity in there.
In the shop it ranges from 95 to 115 depending on what dryers are on and such.
Also from doing some research on the Murakami site, i've found out that i've been emulsioning screens wrong for about a decade. So i just coated about 20 using this "correct" method according to this picture. so...i'll have to report back tomorrow or Monday in terms of washout with this correct EOM.
-
bumping this back up to the top, to see if anyone else has any ideas!
-
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.
-
bumping this back up to the top, to see if anyone else has any ideas!
Try a different emulsion? Bad batch of emulsion?
-
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!
-
Ulano RLX is a lot easier to reclaim with post exposure...I am stuck in vellum hell, with it's inferior density/lack of carrier transparency, my images are almost always slightly under-exposed out of the "burner"...a little time in the sun to get em fully crosslinked does seem to help later at reclaim time.
-
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.
-
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.
-
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.
-
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
-
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.
-
Eric, I got tied up today. Sorry. I'll call you tomorrow for sure.
-
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?
-
I'd say it's possible, but we just recently switched to easi strip, from cci-genzyme
-
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.
-
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.
-
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?
-
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.
-
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
-
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
-
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.
-
Ok. I think you need to look at another emulsion just to try and figure this out. It doesn't really matter who you get it from but a similar product would be best for comparisons. Unfortunately I have no experience with the emulsion you are using so I don't know what to recommend; is this definitely a 1 pot emulsion that you add diazo to for more resistance in discharge/water ?
-
Nova is an extremely high solids high detail pure photopolymer emulsion.
-
Eric have you thought that maybe the pump on your pressure washer is aged now, something to add to the equation...
-
I know this is an old thread, but I've not seen a resolution for this elsewhere.
Eric, is there anything you've found on this topic that would be helpful?
Let me say, I use CCI WR25 on everything. I see a little diazo staining, but it works for my needs without needing hardener for my shorter run WB Discharge and plastisol is easy.
I keep Gemzyme in the tank, and HR30 ink removal prior to that.
I don't get lockup, but my DIY solids filters clog up pretty quick. I OFTEN have screens that dry COMPLETELY between ink removal and the trip to the dip tank for emulsion removal, since it is two completely separate steps in my shop. It doesn't seem to matter...but I *think* letting them dry may help preserve the Gemzyme's purity.
I'm just curios to see what you've found.
Stan
-
I have actually. It was a number of things, everything from chemical reactions to over and even under exposure. Once the CTS came in, we made this, and we started having this issues, we spent a good two weeks looking at everything we could.
Ultimately it took about 20 screens to lock in our step wedge test, but once we did, we haven't had an issue since. We've even switched emulsions two or three times since then, and have it all locked down in a matter of minutes now.