In my previous post, The Bin-cam pincam, https://donaldtainsh.wordpress.com/2019/10/09/the-bin-cam-pincam/ I created a pinhole camera from a redundant food-waste caddy and exposed a sheet of Harman Direct Positive Paper (DPP). The resulting image was fogged and I subsequently set out to discover the source of the problem.
The paper had been loaded in my darkroom under the glow of my red safelight. It is an AP ‘Dark Red’ light, basically a mains powered 15W lamp with an appropriately coloured plastic cover. I have previously found that DPP can be fogged by over exposure to the safelight but have never attempted to quantify the ‘problem’.
Furthermore, the plastic of which the food-waste caddy is constructed is well weathered and I wanted to assess if and by how much the opacity of the plastic had been affected by the weathering.
I started with a 10″x8″ sheet of DPP from the same pack as had been used for the original image. In total darkness I cut it into approximate 5″x4″ sheets, two to be used for testing, one as a control and one as a spare.
My first test was to expose one sheet in the darkroom as a test sheet at five-minute intervals. The safelight was positioned 2 metres away, just above the level of the test strip gadget. When developed, I was surprised at how sensitive to the red light DPP was:
It may not show too clearly here but just five minutes was enough to visibly fog the paper!
In complete darkness I placed a second sheet inside the Bin-cam pincam and put the camera outside in bright autumnal daylight for three hours. The lid and shutter remained closed for the duration of the test. This sheet was developed and compared against the above test strip and the third sheet which was developed completely unexposed.
Again, it may not show clearly here, but there is visible fogging of the ‘exposed’ sheet compared to the unexposed control sheet, comparable with the 5-minute test strip.
The paper of the original Bin-cam image was exposed to the safelight for two to three minutes while being loaded and the exposure was made in bright sunlight. From my tests, the paper would have been fogged to some extent both by the safelight and the less than perfect opacity of the camera.
With the knowledge I now have, I can take steps to minimise fogging in future, primarily in loading the paper but perhaps also making some alteration to the camera with paint or lining paper.
… Or I can live with it and find pleasure in serendipitous imperfection!