Have any of you had long exposure times w/ Murakami Photocure Pro?
I've had my Murakami Pro for about 4 months now and even in the first month my exposure times where pretty high. They're about 30-40 minutes. I'm using 2 500W halogens from a 15-16 in height. I have a thin sheet of glass with very dense ink on my film and I get pretty good results. I did a step test with the emulsion starting a 8-20 min and 20min was the best out of the tests yet it was still not completely washing out.
Murakami isn't a super fast emulsion. If the time spent burning screens is a major production bottleneck for you, then you might consider something quicker. If it isn't, then find another problem to solve. You can do other things while you expose your screens. Like, run to home depot for brighter halogens.
The exposure time of a gallon of emulsion can change as it sits on the shelf, settles, gets contaminated, etc. While Murakami outlasts its sensitized shelf life better than some other emulsions, it's still made with a consumer in mind that goes through a gallon fairly quickly. 4 months is a long time for a bucket of emulsion.
I've also noticed that my exposure time gets longer the older my emulsion gets. I've gone from about 22mins to a 35 minute exposure time with 5 F20T12/GRO/AQ tubes. I've upgrading to 10 of the same bulbs in a new box so I think the exposure time will go down.
My question is....does exposure time matter? I really don't care if it takes me 35 minutes to burn a screen and I get good detail in my stencils....
I use the photocure in small batches - I buy quart sizes, sensitize one at a time and store it in a fridge. I've found that after about 4 weeks that stuff gets un reliable. At $17.00 for a quart I'd rather toss that last little bit than to waste time jacking up a burn.
That having been said, I burn a 20x24, 280 mesh screen in about 8 minutes. I'm using a cheapo Ranar unit with blackligts.