Temp Change / Emulsion Breakdown?

[brandon]

Hello People,
Hope everyone had a nice, relaxing holiday and some extra time off. Meant to post this a couple of days ago but just spaced as the past few weeks have been very damn busy. So here goes. We use Murakami Aquasol HVP and it is a great product. Went through several emulsions when we first received our auto a couple of years ago with testing with exposure time, discharge printing, printing long runs, this and that. In our opinion Aquasol works the best for us. We did do a run a bit back of 15k impressions oversized print and not one pinhole breakdown the entire run. Therefore a great product! However, just recently with the change of seasons we started having problems. As in the past few days. I am hoping its just a batch thing or something stupid we are doing. So after a couple of hundred prints we are getting screen breakdown. Not pinholes but complete breakdown. And not every screen, or every mesh count. Which seems a bit odd to me. We go though a gallon every other day and the screens are not marked to said gallon. So with say 100+ screens coated in the last couple of days it could just be a bad gallon. Or not mixed well.

So with every screen after garment run :

1. removing ink and tape
2. go into dip tank. tank uses Franmar One Step (thanks InkBrigade!)
3. reclaim screen and degrease
4. screen dries on racks.

Room is below 40 percent humidity.
Temp maxes out maybe around 60/65 degrees I think off the top of my head. Sorry, totally spacing right now

When coating screens the same person doing the exact same way of coating does the coating. (Say that several times real fast!)

Have not had a problem in a very long time, say over a year and a half once we established the desired routine. And last winter we just turned a space heater on in the screen room and we are currently doing the same. Didn't have a problem then and we shouldn't now.

So please excuse me if I am missing anything, but I think that is a general breakdown of the breakdown if you will. I did run a search on the boards but maybe I missed something. Sorry if this has been posted before by someone else and I didn't see it as I searched thinking I did remember reading about another shop's similar problem. Thank you in advance to any and all posts!

- Brandon

[jsheridan]

With the winter time comes cool air and lower dew points. It sounds like your screens aren't drying properly nor are they exposed enough.
You need to get some heat and fans in there to get and keep your temps in the 70's. You don't  need a big ole' space heater, just a small one will heat a small screen room to well over 100 if it's sealed up good.

[brandon]

With the winter time comes cool air and lower dew points. It sounds like your screens aren't drying properly nor are they exposed enough.
You need to get some heat and fans in there to get and keep your temps in the 70's. You don't  need a big ole' space heater, just a small one will heat a small screen room to well over 100 if it's sealed up good.

Thank you John. Actually for awhile a couple of weeks ago we were accidentally over exposing our screens but brought it back. But just rereading my post I did say that yup, temp is around 60 - 65 degrees in there. So maybe from running the space heater at low we should just kick it full blast. Damn, that's probably it and makes sense. Just with the dehumidifier and being bone dry around 65 last year we didn't seem to have problems. But yeah, it could stand to be a lot hotter in there! Thanks!

[squeegee]

You said a couple of weeks ago you were accidentally overexposing, why was that?  Then you brought it back, so maybe you're under now?

A long shot but maybe something funky is going on with your integrator and/or your bulb could be nearing the end of its life?  I've had exposures go weird on me when my bulb was nearing death, and even though the bulb was still producing light, I think it's UV output was inconsistent, changing the bulb took care of the problem in my case.

And to moisture still trapped in the emulsion, this is where one of those little humidity meters from Lowes Pierre was talking about comes in handy (wonder if he ever tried it?), or the Saati aquacheck

[brandon]

You said a couple of weeks ago you were accidentally overexposing, why was that?  Then you brought it back, so maybe you're under now?

A long shot but maybe something funky is going on with your integrator and/or your bulb could be nearing the end of its life?  I've had exposures go weird on me when my bulb was nearing death, and even though the bulb was still producing light, I think it's UV output was inconsistent, changing the bulb took care of the problem in my case.

And to moisture still trapped in the emulsion, this is where one of those little humidity meters from Lowes Pierre was talking about comes in handy (wonder if he ever tried it?), or the Saati aquacheck

Hey, we recently did install a new bulb. We try and stay on top of our equipment before things go haywire. So we should be good to go there. But that would be a major cause for alarm. And for humidity we do have a dehumidifier and it keeps things under 40% in the room. But I do know that unexposed screens will reabsorb moisture at any chance they can get. I just need to get the temp up in the room well over 70 as John said. I have a hunch that is the problem. And for the overexposure by accident, yup, that was an employee miscalculation. Thanks!

Oh, and yes, we need to pick up one of those little guys for sure

[Monkeysmakemenervous]

hey Brandon and all responding--I'm having the same problem, and I WISH I could say my screens were getting coated the same way every time, but while I'm confidant the variation is minimal, one thing that has changed at our shop is we are now coating with the rounded rather than sharp edge of the trough. The way the screens are breaking down is in a scaling pattern, not just pin-holes. Literally cracking. Does this sound familiar to having too thick a stencil? Has anyone seen this scaling effect i'm describing?

[jsheridan]

hey Brandon and all responding--I'm having the same problem, and I WISH I could say my screens were getting coated the same way every time, but while I'm confidant the variation is minimal, one thing that has changed at our shop is we are now coating with the rounded rather than sharp edge of the trough. The way the screens are breaking down is in a scaling pattern, not just pin-holes. Literally cracking. Does this sound familiar to having too thick a stencil? Has anyone seen this scaling effect i'm describing?

Round edge can put twice the emulsion on the screen which requires longer to dry and double the time to expose.

It's hard to overexpose and is a good problem to have. Underexposure is a bad problem to have with a laundry list of associated problems.

[blue moon]

hey Brandon and all responding--I'm having the same problem, and I WISH I could say my screens were getting coated the same way every time, but while I'm confidant the variation is minimal, one thing that has changed at our shop is we are now coating with the rounded rather than sharp edge of the trough. The way the screens are breaking down is in a scaling pattern, not just pin-holes. Literally cracking. Does this sound familiar to having too thick a stencil? Has anyone seen this scaling effect i'm describing?

I had to think about this . . . I have seen the scaling problem when the screens were not dry enough before exposure. How humid is your dark room?

pierre

[squeegee]

I just thought of something too, is the scaling visible even slightly on the dry emulsion prior to exposure?  If so, I've seen that before and premature breakdown, my feeling is that it's caused by lack of degreasing and or residual chemical in the mesh that has been allowed to dry, but usually only if you can see it prior to exposure.

Hey Pierre, did you ever try one of those Lowes humidity readers to see if it would work?  Just curious.

[Frog]

Hey Pierre, did you ever try one of those Lowes humidity readers to see if it would work?  Just curious.

Yeah, just before posting a tip on how to patch a screen with two small holes in it! lol!

[squeegee]

Hey Pierre, did you ever try one of those Lowes humidity readers to see if it would work?  Just curious.

Yeah, just before posting a tip on how to patch a screen with two small holes in it! lol!

I thought the idea was to file the sharp tips flat to make them innocuous....

[blue moon]

I just thought of something too, is the scaling visible even slightly on the dry emulsion prior to exposure?  If so, I've seen that before and premature breakdown, my feeling is that it's caused by lack of degreasing and or residual chemical in the mesh that has been allowed to dry, but usually only if you can see it prior to exposure.

Hey Pierre, did you ever try one of those Lowes humidity readers to see if it would work?  Just curious.

'did not, but as a matter of fact, was planning on doing it this morning! Followup in a few days . . .

pierre