Speedball Diazo Screen Printing Emulsion Exposure Using Sunlight 50 seconds
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- เผยแพร่เมื่อ 11 ก.ย. 2024
- If you're doing silkscreen printing using a direct photo emulsion such as Speedball Diazo Screen Printing Photo Emulsion, you can use sunlight instead of the recommended 150W clear or BBA No. 1 photoflood incandescent bulb for the photo exposure.
Using sunlight, there's no equipment to buy and no electricity used, and the exposure time is much shorter, about a minute or so. The Sun casts sharp shadows, resulting in crisp edges on your artwork. On the other hand, you can only do your exposure during the day, and the optimum exposure time can vary, depending on the time of day and the weather. We got good results with a 50-second exposure.
To determine the optimum exposure time, it's best to make a "test strip" like darkroom photographers do, as shown in the video. Place the stencil over the back side of the emulsion (the side that will face the paper or fabric being printed). Make sure the image is backwards. Cover it with glass and a piece of cardboard. Set up a board facing directly toward the sun. Place the silkscreen on the board and expose the stencil for different times, like 30-60-90-120-150-180 seconds. Rinse the emulsion in warm water, then examine the exposed regions to find the best time.
The sunlight exposure method also works well with indirect film-based photo stencil materials such as Ulano sensitized emulsions. Remember to make the exposure through the film base side, not the emulsion side.
thanks for the test, this is something i've been wondering about since I don't have the lights I need or the time to test. Thank you
trying this today thank you for a well documented test...
This exactly what I was looking for!
great idea guys! good video very helpful
Appreciate this greatly !!
Thank you for the video.
If you didnt know, glass take away alot of UV, for example you can not get a sun tan through a glass, it´s not easy to get a proper emulsion exposure from the sun through glas, especially not with that thick layer of emulsion you got on that perticular screen.
Can you describe the steps you exposed it outside? The timing I mean
You should have used a solid bar, a Grey scale bar and numbers (or time 30..60..90 etc) along the stencil. That way, when you reveal your test exposure, you will see the quality across 3 diff print styles.... solid, half tone, and more intricate font numerals
Thickness of glass is ?
I used 1/8" thick glass. I think the thickness is not important, since about the same amount of UV light will get through. I put masking tape around the edges to help prevent accidents from the sharp edges and corners.
Thank You !!!
well it is to a degree since glass filters about about 75-80% of UV light - so your exposure through 1/4" glass would need to be longer - i think you guys were overexposing pretty heavily though - you shouldn't need more than 1-5 sec in direct sunlight
if you exposed in 2 sec steps - 0 then 2 then 4 then 6 i think you would see a very different result - much nicer edges and less bridging and less wash time- just my two cents ... 2 sec in direct sunlight is about equivalent to 1 hour under a 100 watt lamp at 50cm