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Metal Halide Exposure Unit

3038 Views 6 Replies 3 Participants Last post by  InterStreme

So I built my first metal halide exposure unit. It went well until I started testing my exposure times.

We started at 1 minute with a halftone image and an exposure calculator. Most of the dots washed out and the calculator said to increase exposure by 2.8 times.

Our second test was at 2 minutes, dots washed out, calculator said to increase another 2.8 times.

Our third test was at 4 minutes, same story.

Our forth and last test of the night was at 6 minutes. We retained some very small dots. Overall I was pleased with the detail but not with the exposure time...at all.

Tomorrow I will try to decrease the distance from the light to the glass and see how the exposure times change.

A few questions:

1. Is it necessary to paint the inside of the unit?
2. What distance from light to glass do some of you use?

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What type of emulsion? How many coats? How far away is your light, how many watts?
Hey Ridgely!

I'm using Ulano Dual Cure. FOrget the model but I'll check. One coat of emulsion on each side. 400W bulb. Right now the distance to glass is 46" (i have a feeling it's too far). Thanks!
With a 400W bulb I would expose for 12 minutes and have it about 16" from the screen for a proper exposure.
My setup with ulano qx-1 dual-cure: 2-2 coats, 26" from glass, 400 watt metal-halide, vacuum hold-down, 2 minute exposure time.
Sorry guys I missed that it was a metal halide. I would go with Ridgely's measurments.
Hey Ridgely!

Thanks for the info. I got some pretty good screens at 7 mins. Some of the really fine detail still washed out. Do you think that doing the 2-2 coats will retain the really fine dots?
1 - 7 of 7 Posts
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