I recently picked up some Polycol One-Coat emulsion, but I've never used the product before. Can anyone give me a rough estimate on what my burn time may be?
My general exposure setup is 4, 500 watt halogen lamps (UV glass still on) at around 24" from the screen, which is under a very thick piece of plex, like this:
I've been generally doing a burn time of around 35 minutes using everything from the Speedball emulsion stuff to Polycol's other similar products to the Speedball stuff.
I also have a light table made using 2, 40 watt bulbs under frosted plex.
I'm a little worried about this product for two reasons:
The faster burn time - I don't know if it'll be, say, *too* fast, making a right-on burn a little hard for me. I do have the Diazo D additive, which I do believe extends the burn time by 4x.
The more aggressive coating - This worries me in two ways - being able to wash out the graphic, after the burn and also washing out the emulsion, after I'm done with the graphic. I'm using the Franmar's Strip-e-do product with fairly successful results.
I do have a power washer, but I'm a little apprehensive to use it, unless I have a screen that just won't give up the emulsion - the threat of blowing out a screen makes me a little trigger-shy, I guess.
I'm generally going to be using 230 - 380 mesh for poster designs on paper/gesso'd canvas, using acrylic-based inks.
It's basically just a new product for me, and I need a little starting point to do some tests on. 5 minutes, or abouts for the halogens? Perhaps, instead take off the UV glass? 2 1/2 minutes for the light table?
Thanks for any guidance.
Edit: Sorry, I spelled, "Polycol" wrong in the subject line - I can't edit the subject, apparently.
Last edited by shirtsoff; May 2nd, 2009 at 08:43 PM.
Reason: Note about mis-spelling
KIWO's One Coat is just that, a very thick premixed emulsion made to produce a very thick stencil with fewer coating strokes on the mesh with a scoop coater.
I am not use what emulsion you are using now, I am making a quick guess that it is a diazo only sensitized emulsion.
Your exposure will be much lower in time if your original comparative product is a diazo only emulsion, most likely with similar thicknesses it will be less than half the time (as long as you have not mixed in the optional diazo component.
Could you give us more info on the original emulsion, and how you are using and or mixing both?
Your best bet of course is to use an exposure calculator or make a step test.
Yeah - I'm sorry I don't have the exact name of the former KIWO product I used - it was a part of a starter kit the supply warehouse, Midwest Sign, gave me, but the burn time was basically the same for it, as it is for something like the Speedball Photo emulsion you can pick up at the art supply store.
Currently, I've been coating my screens either by using a small, square piece of alum. (basically an old sign from the sign shop garbage, with rounded edges) and applying a light coat to both sides of the screen, being fairly careful to have the majority of the emulsion sitting within the screen and scraping any excess. This makes for a fairly thin coating. I think the person who was teaching me this technique was in a school of thought that the only place emulsion should be, was within your screen. Interesting idea, but I do find that coating the substrate side, well is a good thing.
For larger screens, I use a scoop coater and usually do two coats, with a third on the top, simply to scrape excess.
I'm def. down with doing a step test - I just didn't know if I should start at 10 minutes and have one minute steps, or start at 1 minute, with 30 second steps. I'm almost thinking the latter.
Yeah - I'm sorry I don't have the exact name of the former KIWO product I used - it was a part of a starter kit the supply warehouse, Midwest Sign, gave me, but the burn time was basically the same for it, as it is for something like the Speedball Photo emulsion you can pick up at the art supply store.
Currently, I've been coating my screens either by using a small, square piece of alum. (basically an old sign from the sign shop garbage, with rounded edges) and applying a light coat to both sides of the screen, being fairly careful to have the majority of the emulsion sitting within the screen and scraping any excess. This makes for a fairly thin coating. I think the person who was teaching me this technique was in a school of thought that the only place emulsion should be, was within your screen. Interesting idea, but I do find that coating the substrate side, well is a good thing.
For larger screens, I use a scoop coater and usually do two coats, with a third on the top, simply to scrape excess.
I'm def. down with doing a step test - I just didn't know if I should start at 10 minutes and have one minute steps, or start at 1 minute, with 30 second steps. I'm almost thinking the latter.
If the emulsions you used in the past were all "premixed" right out of the can I would agree with you about starting a step test at a higher time, but you may want to start at 5min, while not sure about any of your equipment that emulsion is very fast to expose...
Let us know what happens (I guess, with the limited info about 12 min - just taking a wild guess in the dark thinking that your original emulsion was a diazo only)
My general exposure setup is 4, 500 watt halogen lamps (UV glass still on) at around 24" from the screen, which is under a very thick piece of plex
I dont understand why you would leave the uv glass on ...because the uv is what burns the screen , not the light.....maybe take the uv glass off and your burn time will be alot shorter...also get a 21 step wedge and take the guess work out of burning......
I dont understand why you would leave the uv glass on ...because the uv is what burns the screen , not the light.....maybe take the uv glass off and your burn time will be alot shorter
I've actually acquired the lights from a screen printer who has been doing work for decades - I've been simply following his lead.
I think another reason is, well, it's UV light - doesn't seem to be the best for my own eyes? It may also be a, "it ain't broke, don't fix it" type of situation. The screens have been coming out well enough, without modification - but I'll be happy to get the slave - I mean, intern on it
Quote:
also get a 21 step wedge and take the guess work out of burning......
Sure thing - let me reiterate my initial question - a basic starting point for experimenting given a new unknown
I'll be doing burn tests today and will try to keep good records of my current setup and what I'm getting. I may just keep a , "Book of Burn Times" as a reference for myself.
Today, I think I'll try the halogen lights w/o the UV glass and if I get to it, the black light light table. It'll be a lot easier to do a step test with the Halogens - I don't quite know how I'm going to take the screen off the light table, without slightly moving the graphic, to block out some of the image.
My setup was a little modification of what I've been using:
2, 500 watt halogen lights, at ~ 20" from the screen:
Here's an example of a print from the burn test:
I started with 3 minutes, which did absolutely nothing - the entire coating of emulsion was stripped off. 4 minutes wasn't much better, but 5,6,7 and 8 minutes seemed to have promise, with 9 minutes seeming to be perfect. I tried the test 3 separate times on different screens, with similar results.
Just to reiterate, this is the Polycol One-Coat Emulsion, with the diazo additive, with one coat on each side of the screen. The setup is 2, 500 watt halogen lights (UV glass is OFF) at ~ 20inches from the screen.
I've tested it at work with our industrial exposure unit and I use it at 7 seconds. looks like using the shop lights turns one second into a minute or so. Good to know if i want to do this at home.
Advice on using the Polycol One-Coat Emulsion 
