Editing Exposing Screens (section)

=== Process so far ===

I started with 17" from some website. I think I started with 17 min exposure with a 250W bulb, then bumped it up to 35 min, which I'm realizing now wasn't a long enough exposure because with enough spraying the exposed parts of the emulsion were coming out. 

Doing even longer exposures didn't seem viable, so I got a 500W bulb. 

It seemed like the center of the screens and the edges were behaving differently in terms of washing out the screen, so I tried to figure out what would be the appropriate distance for the bulb. One site says that it should be the same as the diagonal length of the screen (28.6" in this case). I was thinking that if the light spreads in a 90&deg; angle from the bulb, then it should be 1/2 that (Pythagorean theorem). 

Starting with 250W/17"/35 min > 500W/17"/17 min > 500W/28"/44 min. 44 min is too long, so I cheated it and tried 500W/25"/35 min. The exposed emulsion washed out. 

With the next screen I tried using my calculation for the distance (28.6 / 2 = 14 or 15"). I gave it a couple extra inches, which brought it full circle to 17". The equivalent amount of time would have been 16 min, so I arbitrarily tried adding 6 min for 22 min exposure. Too long, but the image washed out the same towards the edges as in the center, so the height might be fine.  

3rd try: 500W/17"/19 min which looks to be the winning combination. Maybe it could be even a little less time for the exposure. <<< yes. 18-&frac12; min.

4th try (& truly winning combination): '''500W/17"/18-&frac12; min'''