Emulsion failure -- heat?

[redwoodtees]

I experienced my first challenge with emulsion failure yesterday. I'm trying to understand the cause. Here is the setup:

180 S-mesh statics, coated 2/1 with CP TEX. Exposed 110S with 5K halogen, and then post-exposed for an additional 220S. The job has three screens. The first two are using Virus Hydra discharge ink. The third and final screen is using Green Galaxy Comet White. First two screens, 1 hit WOW. White screen, PFP.

The white screen is the one that's failing. But it does not appear that the white ink is causing the failure -- it's failing in the area where the discharge ink is picking up on the bottom of the screen. The emulsion is literally dropping away from the screen wherever the discharge ink picks up on the bottom of the screen. I went through two screens with the exact same failure.. each one lasted about 25 impressions. I have used this emulsion with Virus Discharge for a couple years with zero issues. And the screens containing the discharge ink are fine.  The thing I DON'T use very often is the flash. So I'm wondering.. is heat what's causing the premature failure?

Planning to get some hardener today.. Hopefully that will fix it. But I am curious if there is a known correlation between heat and emulsion failure, or if there is something else going on.

[Frog]

I have no idea about the emulsion/ink combination you are running, but my experience is that heat tends to harden (or act as a pre-exposure) rather than causing breakdowns.

[redwoodtees]

Just spoke to Chromaline rep.. He had the following to say:
1. Since my drying cabinet is not heated, my shop is not heated and it's winter, there is probably moisture in the emulsion which is keeping them from fully crosslinking. He suggested heating the screens with a space heater for a few minutes prior to exposure
2. I'm probably under-exposing (I did exposure tests, but he says CP tex probably needs at least 2 minutes with a 5K halogen
3. I'm wasting my time post-exposing a Diazo emulsion. This was news to me.. He says once the screen is exposed, it's "done" -- it will not continue to harden post-exposure.

[3Deep]

I don't have heat in my drying cabinet either, but I installed a small fan I bought from Walmart and it drys the screens pretty dang good, or put a fan in front of the doors if you don't have room to install the fan on the inside of the cabinet.

[redwoodtees]

I have a fan in my drying cabinet. Just no heat. I have always felt like my screens were pretty darn dry. But I'm going to try to figure out how to integrate a heater (hopefully without burning the shop down)

[mk162]

Well since moisture levels are lower in the winter because the air is colder, I doubt it's that unless it's been particularly rainy.

Skip the heater, use a dehumidifier.  it will heat up the space as well as take the moisture out...win-win.

[Sbrem]

We have a pretty old screen dryer, a commercial one bought at auction, has a heater and a fan, coated screens are ready in 10 - 20 minutes depending on mesh count and coat thickness.

Steve

[Maxie]

I would suggest that you control what could be afffecting you screens.
Humidity
Drying temp
Expose with a step wedge to make sure you are not under exposing.

[Prints Charming]

We have a large screen drying box Aprox 40 screens(half for manuals other side for autos). We have a turbo fan at the back behind a peg board that moves air throughout cabinet ,a large fan in the bottom with a vent on top and bottom,plus a small space heater on low. we also have a hydrometer to see humidity levels and temp in box.

[tonypep]

Just spoke to Chromaline rep.. He had the following to say:
1. Since my drying cabinet is not heated, my shop is not heated and it's winter, there is probably moisture in the emulsion which is keeping them from fully crosslinking. He suggested heating the screens with a space heater for a few minutes prior to exposure
2. I'm probably under-exposing (I did exposure tests, but he says CP tex probably needs at least 2 minutes with a 5K halogen
3. I'm wasting my time post-exposing a Diazo emulsion. This was news to me.. He says once the screen is exposed, it's "done" -- it will not continue to harden post-exposure.

Correct on all three

[redwoodtees]

Second print attempt was successful. We heated the screens before exposure, increased exposure time, and used an emulsion hardener. Not very scientific, but the job is done . I learned a lot from this.. thanks to everyone for their input.

[mooseman]

I have a heated drying cabinet but thinking about going bigger. Recently I saw this gadget on the TV and thought it would be a great device to add to a drying cabinet. All you need to do is have an outlet, (inside the cabinet) to plug it into.
There are multiple sources for this heater with a wide range of prices but it could be pretty neat for a drying box setup.
here is the best price going at @ $30.00

https://www.neweasy.com/product/handy-heater/?ref=gmerch&autoplay=1&upcid=2553&gclid=CIuFlMaiitECFQiMaQodO0UDsA

mooseman

[Maxie]

Looks good but make sure it doesn't overheat the screens in a small cabinet.

[jsheridan]

Well since moisture levels are lower in the winter because the air is colder, I doubt it's that unless it's been particularly rainy.

Skip the heater, use a dehumidifier.  it will heat up the space as well as take the moisture out...win-win.

Yes!

Heat doesn't dry emulsion, removing the water is what dries them.

[bulldog]

Well since moisture levels are lower in the winter because the air is colder, I doubt it's that unless it's been particularly rainy.

Skip the heater, use a dehumidifier.  it will heat up the space as well as take the moisture out...win-win.

I also second this. You'd be surprised how hot it can get with the dehumidifier in a cabinet.