Screen Issues - Need some help here

[cleveprint]

OK, got some issues here in the shop the last week and a half. We are getting screens breaking down like crazy out of nowhere. Im wracking my brain and we cannot pinpoint anything that would be causing it. We've been on the same screen cleaning/coating/exposing cycle for the last 3 years at least.

Aquasol HV Emulsion - Starlight Exposure Unit. Typical exposure time is in the 7-8 seconds range (we have upped this a hair on a few jobs this week too and still the same issues). Film.  We have been rock solid with no issues. Spot color stuff, so its not as if we are underexposing to keep the halftones. Mainly the 125's and 160's are breaking down, but thats also 75% of the mesh we use so I guess its more noticeable in those meshes. Same guy has been coating for the last 2 years, so I highly doubt that its a technique issue.

Chemistry - Korchem dip tank emulsion remover and Korchem ProClean dehaze/degreaser. Again, the only issues we've ever had in the past has been if they aren't rinsed well after dehaze. I myself have done the last two batches of screens and Im making sure they are done well.

Has it been hot in the shop? Sure but nothing out of the ordinary for this time of year. Some days hot and humid, others not. We typically give our screens at least 24 hours to dry as well.

Let me know if anyone has something Im missing!

[Frog]

Same technique as usual notwithstanding, how about some exposure tests?

[Squeegie]

My first thought is this;

We typically give our screens at least 24 hours to dry

Dry is a funny term when talking about screen emulsion.  I would suspect humidity is the culprit. The screens can sit for 4 or 5 days, but if the environment they are in is not correct for your emulsion to properly dry before exposure, you may still have issues.

Best of luck,
Bill

[cleveprint]

My first thought is this;

We typically give our screens at least 24 hours to dry

Dry is a funny term when talking about screen emulsion.  I would suspect humidity is the culprit. The screens can sit for 4 or 5 days, but if the environment they are in is not correct for your emulsion to properly dry before exposure, you may still have issues.

Best of luck,
Bill

By no means do we have a perfectly temperature controlled screen room, but we've been doing this a long time and its been much more humid and hot than it has the last two weeks. To be honest, its been a little cooler than earlier this summer! But I agree thats something to look at. But why its rearing its head now out of the blue is whats making me nuts!

[Homer]

I've had bad batches of emulsion before...one bucket was orange peeling out of nowhere. I'd try a different emulsion first, then look at other chemistry...

[kirkwad]

We've had this with too much humidity. Especially if you have coated screens sitting around for a period of time. Putting a dehumidifier in your coated screen area will help. It's a good idea to have a hygrometer so you're aware of the humidity in the environment. Also making sure the mesh on your reclaimed screens are completely dry before coating. You may have something else going on, but that's a good place to start.

[blue moon]

Call Matt at 440 942-6055 to come and test stuff at our place. We can coat,  burn or what ever you need. I am out of town for another week so talk to Matt, but I can help upon return.
Pierre

[cleveprint]

Call Matt at 440 942-6055 to come and test stuff at our place. We can coat,  burn or what ever you need. I am out of town for another week so talk to Matt, but I can help upon return.
Pierre

Thanks Pierre. Ill hit you up if we are still running into problems.

Bought a humidifier last night and its been running all AM. Level seems to be hovering around 50% after running it for a while. Re-did all of our coated screens, re-coated them, changed the water in our exposure tank, started a new gallon of emulsion, got a new batch of Dehaze/Degreaser.... Im trying to cover all bases to see if we can get back to normal. Taping the crap out of screens mid-run is getting old quick!

[ABuffington]

Al from Murakami here.  Have you changed coating technique at all, or the personnel that does the coating?  Try 1:1 sharp edge with a slow firm coat. 


Our test times on a starlight was done on a table top model with glass.  If you are using an STE direct to screen and no glass the times will be about 25% less.

Humidity is always a concern, but we don't have a dehumidifier here in our lab (go figure after all of my screen room rants on getting one!  but then we don't do production here and I'd have one for wb ink printing.)

Check coating technique, try these times above.  Post expose in sun when possible.  Allow adequate dry time.  Dry to the touch only tells you if the surface is dry, the inside can  like jello if rushed to press. 

If you are still having issues, call me, 323.697.4334 cell. 

[ABuffington]

I also recommend using MS Degreaser from us.  This is a miracle degreaser that can help clean very old screens that have seen a ton of plastisol.



Here is a photo of how a well degreased screen should look.  Notice the water drops and areas where the water runs around contaminants that are totally invisible, then compare to the photo on the right where the water 'sheets' off the mesh.  This sheeting action is a sign of a well degreased screen.  Combo products may be causing the problem.  Degreaser/haze combos can work if rinsed well, but MS Degreaser is far superior in cleaning and allows halftones to adhere better as well.  We make a system that is tested for compatibility, MS Degreaser is one of the best products I have come across for fixing pinhole issues.

Al

[cleveprint]

little update here if anyone cares. pretty much re-did everything in the screen cycle. reclaim dip tank cleaned and started fresh. new batch of dehaze/degreaser. new brushes, buckets, etc. fresh gallon of emulsion, not that it matters too much as we are going through a new gallon every few days. upped exposure times about 20%. dehumidifier in the screen room. seems to be keeping the humidity level at about 40-45%. Was reading at about 60% earlier this week.

We haven't had any screens breakdown this week. So my best guess would be to chalk it up to the screens not properly drying all the way. Although it was nice to refresh the entire process. I could see the humidity being the issue we were having. But also, we've been doing this same process with no dehumidifier for a long time and never ran into issues.

Al, one thing about your exposure chart you posted. When you do that, is that to get a full exposure on a screen actually exposing an image? When I take a 125, white mesh and expose it for 18 seconds, Im having some major washout issues. registration marks do not wash out. any small details do not wash out. def over exposed. our films are pretty dark as well. I get that thats where you are probably getting a full exposure of that emulsion, but for actually producing a useable screen, Im not sure that works for us.

[Maxie]

The exposure times on white and yellow meshes are completely different.
I have some 110 white and I expose for the same time as 230.
I find that the best test is a 21 step Stouffer exposure strip.

[ABuffington]

Yes the times I give are for a max exposure here, in LA with 50-60% humidity common.  Ambient conditions in the shop, coating technique with sharp or dull, humidity or lack of humidity can all affect times.  If you shoot with dense black positives and see undercutting of details, then adjusting time isn't going to hurt. But any adjustment on an LED is a huge adjustment when seconds are taken off. HV or HVP can be post exposed in the sun or back on the light table for added durability.  There should be no slime or emulsion color coming off with a white wrag with your chosen exposure time.  If there is you can check coating technique.  1:1 dull could change to 1:2 sharp for a little less, or 1:1 sharp if run lengths are short.  1:1 sharp yields about 5-6% EOM, 1:1 dull 12-15%.  A thinner coat can help on LED>

[tbarnes]

A dehumidifier was the perfect first step to combat this, if you are really serious about your screens (you should be) I recommend a moist meter. They go for less than $200 and you can use it forever to check the moister in the screen. That will keep you from wasting money on replacing chemical, emulsion, etc. and chasing your tail when you have breakdowns. In my experience, they are almost always linked to humidity levels, temperature is usually irrelevant.