Help me understand why my emulsion is locking up

[Frog]

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.

[Gilligan]

We use different methods depending on mesh or the eom we are striving for.

[sqslabs]

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.

[mimosatexas]

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.

[Inkworks]

WHat kind of exposure unit do you use?

[ericheartsu]

WHat kind of exposure unit do you use?

we were using a richmond soalr bearm 7k, but now use an I-image STE II

[ericheartsu]

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

[ericheartsu]

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.

[Printficient]

Eric quick question.  What amount of heat if any are your screens exposed to.  Any type of heat (wet or dry)

[ericheartsu]

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.

[ericheartsu]

bumping this back up to the top, to see if anyone else has any ideas!

[bulldog]

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.

[IntegrityShirts]

bumping this back up to the top, to see if anyone else has any ideas!

Try a different emulsion? Bad batch of emulsion?

[ericheartsu]

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!

[Grumpy Ole Artist]

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.