Little Strings in Emulsion While Coating?

[print3r]

Hi! My manager just showed me this site the other day. It's awesome that there's a forum for everything.

We use a Uni-Kote and Chroma Blue to coat our screens. In the past few weeks, I have noticed a lot of little strings getting stuck at the edge of the emulsion vessel (sorry, I don't know the proper name for it) and subsequently sometimes getting stuck in the coating. Like, a lot. Maybe one or two will show up. either on a screen or on the edge of the vessel, every two or three screens while I'm coating them. I'll find them on the edge of the vessel, on the screen, or sometimes floating in the emulsion. They're usually maybe half an inch long, pretty small.

It's a pain to pick them off and stay vigilant for them, and I also hope the screens aren't getting plucked of their threads while they're being coated or something. TBH, I'm still pretty new to this stuff, so I'm at a loss for how to troubleshoot it. I have one semi-guess: I know another guy here uses the thin, sharper edges to coat screens, while I use the fatter, rounder edges of the vessels. Perhaps the thinner edges are scraping at the screens?

Sorry if any of the language is unclear; like I said, I'm kind of new and haven't picked up on all the jargon. I'd appreciate any advice!

Edit: To clarify, the strings are all completely detached from the screen.

[Jwcontractscreen]

Sounds like it is from your scrub brush from washing the screens? We get these sometimes. It usually happens with new brushes. If you flood rinse your screens as a final step at an angle and watch the water sheeting down the screen, you will find imperfections like those, or any small tears in the mesh.

[Frog]

I think that you need to nail down whether they are "in your emulsion" or on the screens, perhaps, then causing cross-contamination.
Is this constant? Even after cleaning out the trough and refilling with fresh emulsion?

[blue moon]

If you have long time gaps between each screen, the emulsion dries on the coated edge and creates strings of dried up emulsion. Those tend to end up on the screen and look like what you described.
Post a picture, it will help figuring it out.

Pierre

[print3r]

Thank you for your replies!

JW: I'll have to see about that, I don't know much about the reclaim process. I think the strings are from the screens, but it's worth looking into! Also, Kentucky printers represent! :-)

blue moon: I know what you mean re: dried strings of emulsion, and it's not that. Pictures are a good idea--here are some I found in a session of coating about 20 screens. http://imgur.com/a/4F17a These ain't even all of the ones I found.

Frog: I think they're coming from the screens, not the emulsion, though we pour leftover emulsion from the trough back into the emulsion bucket, possibly/probably causing the cross contamination you describe.

Today I used fresh emulsion though, and got the results linked and pictured above. They definitely seem to come from the screens!
My manager guesses they might be the results of flyaway threads on the edges of the screen, but the trough only touches the centre of the screen.

I hope I'm replying correctly, I haven't used a forum like this in a while haha.

[Orion]

Check brushes/scrubpads used for screen reclaim to see if they are shedding. If unfiltered fans are used to circulate air in the screen room they may be the culprit. Moving screens from reclaim to screen room through the shop could be something to look at too.

[print3r]

JW and Orion: I think you were right! I looked at the scrub brush being used in reclaim and the little white hairs that (freely) came off of it were identical to the ones I'm finding on my screens.

I don't think I could convince my bosses to change the brushes though. Do you guys think I should just wipe over my screens with a paper towel or something before coating them?

[Frog]

JW and Orion: I think you were right! I looked at the scrub brush being used in reclaim and the little white hairs that (freely) came off of it were identical to the ones I'm finding on my screens.

I don't think I could convince my bosses to change the brushes though. Do you guys think I should just wipe over my screens with a paper towel or something before coating them?

tac rags like used in paint prep used to be the insurance to make up for less-than-stellar housekeeping

[244]

JW and Orion: I think you were right! I looked at the scrub brush being used in reclaim and the little white hairs that (freely) came off of it were identical to the ones I'm finding on my screens.

I don't think I could convince my bosses to change the brushes though. Do you guys think I should just wipe over my screens with a paper towel or something before coating them?

You can't convince the boss to change the brushes? Why not? Every bad screen pays for a new brush for sure!

[blue moon]

those are clearly caused by the brushes. If your boss will not let you get rid of them, find better brushes.

pierre

[Mr Tees!!]

...those are definitely fibers from the scrub brush. The ink/stain removers we all use inherently break these brushes down over use.

Try this: get a gallon bucket and fill it with just enough water to partially submerge a scrub brush. Add a small splash of Simple Green cleaner to the water. Put a NEW scrub brush in the bucket and use this as a final step in your reclaim. Do a quick scrub on both sides, powerwash and flood rinse.

Be sure to use a DEDICATED brush for this. You don't want much cleaner added at all to the water (you don't want excessive foaming/sudsing, just enough to break the surface tension of the water.Shoot for light bubbling as you scrub)

I change the solution out after about 20-30 screens, or when it starts to look cloudy.

Yes, its an extra step, but its quick and worth the results. Give it a try and judge for yourself!

[3Deep]

I've had those and I just use a sticky lint roller on the screen before emulsion is applied, they are hard to see sometimes if you not in a good light during reclaim.

[Maxie]

Simple solution, use scrub pads.     We don't use brushes at all.