[chizepe]

Hi there, been pulling my hair out the last couple of days. Found a unopened quart of Prochem WR-14 emulsion that I purchased last July. I figured it maybe be questionable to use at this point, but the place I ordered it from figured it would stilll be good. I actually ordered a new quart but it’s too cold to ship atm and I need a screen made ASAP. I mixed up the emulsion and coated a few screens and can’t seem to get anything to wash out. The stencil appears but won’t wash. I ran a makeshift step test I ran tonight and have included a picture. I exposed from 5 mins at the top to 1 at the bottom and still nothing will wash out. I’m using an X-factor vacuum exposure unit and have doubled up my films. Screens were coated one on the shirt side and 2 on the ink side. I’ve looked over these forums and google and nothing seems to work. Hoping someone here with more experience can shed light, thanks for your time.

 

[NoXid]

Emulsion is like film (you know, the stuff you used to need in a camera in order to take a photograph), when it goes bad, it fails to expose. In the case of emulsion, that means all the emulsion on the screen would wash out. Your emulsion is not bad.

Your films may not be dark enough (needs to be opaque to UV light). Maybe post a photo of a film and tell how you are printing them.

 

[chizepe]

Here are pics of the positive. I doubled them on the last exposure as I think you’re right about them. Got better results but still nothing that washes out. They were printed on an Epson 1430 with no rip software.

 

[chizepe]

Also starting to wonder if I am coating the screens too thick. I am coating one on the shirt side and two on the ink side. Thinking I should maybe do one and one and then hit one side with the edge of the scoop coater to clean it up. In the past I’ve genarally coated this way and has no issue but in the past was using a less water resistant emulsion and a better exposure unit.

 

[bpfohler]

We coat 2/1, it's not too thick. Over exposure, have you done a step wedge test?

 

[FlashDave]

I know from experience that some emulsions don't like any heat while drying, I had the same issues with the burnt image appearing but not washing out, due to a fan heater on its lowest heat setting making the emulsion crosslink. I think this mainly is an issue with Photopolymer emulsions however Diazo based emulsions could also suffer.

 

[NoXid]

If it were too thick, again the problem would be under exposure, not over exposure.

The comment above about too much heat while drying might be something to check. I use some heat while drying and have not had a problem, but my understanding is that it can be a problem. Also maybe some light leaking in during drying and causing the emulsion to partially expose?

 

[jshirey34]

We keep the screens in a “dark room” until we expose and rinse out to protect the stencil. Also after emulsifying we use regular fans with no heat to dry. We’ve had problems in the past using a heat source while drying after coating.

 

[Sulp]

Film looks fine. Coating seems correct. We coat 1/1/1. Basically 1 one on the inside/squeegee side. 1 on the back, and then finish 1 on the inside (always finish on inside no matter how u coat). The emulsion u used is a 2 part emulsion. U say it was on the shelf for a year..Was it sensitized a year ago as well? If so it’s definitely the emulsion. Shelf life after emulsion is sensitized is only a couple weeks.

 

[alrozac]

We were having a bunch of issues as well with different emulsions. We switched to ChromaBlu about a year ago and have not had any issues yet. It is a ready to go emulsion where you don't need to add the sensitizer. Even when printing larger quantities it holds together with no issues.