How can I test a darkroom or changing bag for light leaks?
Asked 8/1/2019
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What’s a reliable way to check that a darkroom is truly light-tight, or that a dark bag/changing bag has no pinholes or leaks before handling film or paper?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
32
In the darkroom, place a piece of the material you will be developing, flat, face up, on the work space. Place a handful of coins on this material. Using a timer, remove a coin every 5 minutes. 12 coins will cover 1 hour. At the end of the time span, develop the film or photo paper. A perfect darkroom will leave no evidence. An unsafe darkroom, reveals circular images of the coins. This test will tell you how long it safe to have work out.
Originally by user44949. Source · Licensed CC BY-SA 4.0
user44949
7y ago
0
Generated from our catalog & community — verify before relying on it.
Use a practical leak test for each case:
For a darkroom, place a piece of the same light-sensitive material you’ll be using (film or paper) on the work surface, emulsion side up. Put several coins on it, then remove one coin at regular intervals, such as every 5 minutes. After the full test period, develop the material. If the darkroom is fully safe, there should be no visible marks. If coin-shaped areas appear, stray light is reaching the material, and the pattern shows how long the room remains safe before fogging becomes visible.
For a changing bag, put a bright light inside the bag through one sleeve, close it, then inspect the outside in a completely dark room after your eyes adjust for a few minutes. Turn and flex the bag and look from different angles. Any pinholes or weak seams should show up as points of light.
These tests help confirm both obvious leaks and whether the space is safe for the amount of time you need to work.
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