 DIY Free Exposure Unit AKA "The Sun"
Here's a little tutorial I wanted to put out there for anybody who is looking to get into silk screening; maybe for themselves as an experiment or who just do not have a proper exposure unit and are monkeying around with low uv output lights and long exposure times.
The Sun is your friend. Exposure times vary from 20 seconds to just under a minute. Using a few different emulsions AutoType's: Autosol Classic & 8000 and Ulano (I can't remember which one) at noon on a sunny day, I typically encountered exposure times around 30 seconds.
At 8:00AM and around 4:00pm the exposure times increase by up to 10 - 15 seconds
ON an overcast day the UV is still coming through the clouds hence why you can get a sunburn even if the sun is not directly on you. I have found that times increase in general by about 50% or (at noon) 15 seconds.
When I first started to do this I was using a piece of glass to keep my film in contact with the screen. This quickly became impractical as I found that even aluminum frames were not completely flat and the artwork would end up raised or lifted in one area or another at times. Not to mention the several sheets of broken glass that happened as I rushed to wash out the screens in the shade with my garden hose.
The solution?: Spray Flash adhesive. Whenever I do this I typically accept that my film will have a shorter life span- as I am putting adhesive directly on the film. However - if you print your film "backwards" (Emulsion Down in Adobe Illustrator) you can clean the adhesive off the transparency - careful not to let press wash or whatever you decide to use for clean up go on the INK side of the Film.
That being said; after you've sprayed the adhesive on the film allow it to dry for 30 seconds or more so that it has a light tack, akin to a post-it note. In a low light setting place your film on the outside (print side) of your screen, take it outside with a swiftness - avoiding light (you can box it or bag it or just be quick) and expose the screen directly to the sun. After 30 seconds bring it to a shady place OR indoors where you can wet down both sides of the emulsion and wash out the unexposed areas.
Simple as that.
IN order to get the best results I recommend testing this method at your particular location taking time to note the time of day as well as sunlight conditions and the day of the year. UV varies in intensity in parallel with the seasons. Use a film test pattern at first with your particular emulsion/film/screen combination that you expose in intervals of 5 seconds. I imagine someone else has posted exposure testing instructions - If not I'll cover that in a later post.
Good luck and have fun. Information, ingenuity and resourcefulness can get you over most of the hurdles that you encounter. When you are first getting into Serigraphy (the art world name for silk screen printing) it doesn't make much sense to drop a lot of coin discovering if this is something that you want to do. This can be a fun, rewarding and sometimes frustrating endeavor. But so long as you learn from your mistakes and reference resources such as t-shirt forums - It seems implausible that anything you attempt to do is impossible. Professional equipment simplifies matters but the same essential principles apply to silkscreen printing regardless of how it is being done.
Good Luck and I hope that this post helps introduce some people who are just peering into the world of silkscreen printing walk right in.
Regards,
Christopher Tod
Last edited by christophertod; July 16th, 2009 at 05:18 PM.
Reason: typo
| 
