Reclaim Hardened Screens (Split from Starlight Exposure Unit Equipment Thread)

[PylonPress]

Recommendations based on my shop's previous troubles:

- Give your screens an extra coat of emulsion.  We coat 2/1 round side.
- Burn for 75% longer than you are now for discharge/wb screens.  Aquasol HV has a very wide exposure latitude and with good films you can push it pretty far before it locks up.  We almost doubled our exposure time on a 10k MH unit and the image still opens beautifully.
- Use some type of reclaimable hardener, Murakami makes one called MS Hardener.  We soak our screens with it and throw them in the sun for a bit.

We use Aquasol HVP without diazo and no longer have any issues with screen breakdown, even on very long runs.  I know this doesn't pertain to the Starlight specifically, but you should see a major difference regardless of the exposure unit you are using.  We've also done test runs without the hardener and haven't seen breakdown with the longer burn times, but we use it anyways as a safeguard.

Perfect thanks. I am going to have to experiment with it and report back.  I am certain its me and not the exposure unit because I had the same issues with my UV unit.   

Brett do you have trouble reclaiming screens after you add hardener to it?  I know there are different types of hardener, one that can be reclaimed and ones that permanently lock up the emulsion.  We usually don't do over 200-300 prints so its not like we expect it to last 5k impressions.

[sqslabs]

Brett do you have trouble reclaiming screens after you add hardener to it?  I know there are different types of hardener, one that can be reclaimed and ones that permanently lock up the emulsion.  We usually don't do over 200-300 prints so its not like we expect it to last 5k impressions.

We learned this the hard way (no pun intended) and lost more than a few screens before finding the right stuff.  The Murakami "MS Hardener" is reclaimable and CCI makes also one called Hardener X which I've heard plays nice with Murakami emulsions as well.  We get our MS Hardener from River City Graphic supply.  Roeder in Orlando also carries it but haven't had stock lately.  The CCI stuff can be purchased through Tubelite. 

We use a dip tank for reclaim which I'm sure helps a bit with the hardener, but I doubt it matters much either way.  I've also found that the sooner you reclaim a hardened screen after use, the better.

I have a gallon of MS Hardener coming in today.  Would be happy to give you a sample to try out if you want to give it a shot.  Let me know.

[ABuffington]

As mentioned, Murakami MS Hardener will leave the screen reclaimable.  I often recommend using our ER-605 or Super Strip at double strength to help soften the emulsion.  Dip tanks work very well for this purpose. 

One area that also helps a pure photopolymer in the reclaiming process with an emulsion like Aquasol HVP is to post expose the screen.  SBQ sensitizer remains sensitive after development.  If you hit it with Screen Opener, MEK, Acetone, Mineral Spirits, you can flash these underexposed sensitizers and make reclaiming difficult.  Post exposing helps cross link all sensitizer for an easier screen reclaim.  Too often emulsion is underexposed and if not post exposed it can be difficult to reclaim pure photopolymer emulsions. 

For extremely hard to reclaim screens, you can apply Murakami HR-700 caustic haze remover to the emulsion on both sides of the screen, (Always wear personnel safety equipment).  Let it sit for 5 minutes, rinse off carefully with a hose to avoid splash back.  Then put it in a 2x strength dip tank solution, or apply emulsion remover with sponge to soften emulsion for reclaiming.

Alan

[Frog]

As mentioned, Murakami MS Hardener will leave the screen reclaimable.  I often recommend using our ER-605 or Super Strip at double strength to help soften the emulsion.  Dip tanks work very well for this purpose. 

One area that also helps a pure photopolymer in the reclaiming process with an emulsion like Aquasol HVP is to post expose the screen.  SBQ sensitizer remains sensitive after development.  If you hit it with Screen Opener, MEK, Acetone, Mineral Spirits, you can flash these underexposed sensitizers and make reclaiming difficult.  Post exposing helps cross link all sensitizer for an easier screen reclaim.  Too often emulsion is underexposed and if not post exposed it can be difficult to reclaim pure photopolymer emulsions. 

For extremely hard to reclaim screens, you can apply Murakami HR-700 caustic haze remover to the emulsion on both sides of the screen, (Always wear personnel safety equipment).  Let it sit for 5 minutes, rinse off carefully with a hose to avoid splash back.  Then put it in a 2x strength dip tank solution, or apply emulsion remover with sponge to soften emulsion for reclaiming.

Alan

As a veteran of caustic haze removers, I'd be very hesitant to use this on your already fragile "S" mesh. care to comment?

[ABuffington]

When using caustic haze remover the time on screen must be monitored.  Anything over 5 minutes does present a danger to fine threads.  Multiple uses of caustic haze remover will also weaken threads.  Caustic haze remover use should be minimized.  Consider 300/T is a 34 micron thread, 150 and 180 have a 48 micron thread, 225S is a 40.  So even in the popular S meshes the thread is still bigger than a 300-350 which gets used a lot for sim process and suffers from haze more due to the increased number of mesh knuckles.

Some tricks to avoid using hardener at all:
Expose Murakami Emulsion for as long as you can without undercutting details.  More light = more strength as long as undercutting is not observed.
You can use double diazo.  We recommend 8grams per gallon.  You can push this to 16grams per gallon.  This will also lengthen exposure time by 25% more time when you double the diazo load.  Always perform a step test or calculator test to determine what works for your shop.  I can have 2 shops with the same exposure unit and emulsion and get 2 different times.  Why?  Humidity in the shop and moisture in the screen affects exposure time, more humidity, more time. My clients in AZ using Aquasol HV can expose in 15 seconds on a 5k metal halide due to 10% humidity and high 90 degree temps, while a customer in Panama may need a full minute at 90% humidity and 90 degree temps.  Coating also may not be the same, thicker coats more time, thinner coats, less time.  Bulb in unit may be old while the other is new.  Voltage in the shop may not be the same.  Screens may not have been dried as long in one shop as another.

At some point it is cheaper to cut out the mesh.  We don't get these print runs much, but at 20-90k it may be far less labor and cost just to restretch than to tie up reclaiming with 20 minute hard reclaims along with all the chemistry needed.

Al