Keep the Light Out!

July 9, 2010

Last night, at about 11pm, I finished building the light baffle for the “darkshack’s” ventilation system. Here you can see its half-finished state with a baffle directly under the fan output. I built a second baffle to the right on the bottom then flacked it with black spray paint before covering it up. Since the shack’s in rough shape, I was going for cheap and functional, not pretty and slick. I’ll be covering it with left-over scrap shingles from the roof job last weekend.

The recommended airflow for a darkroom is a 10x turnover rate. You can compute this by measuring length, height and width of the space, giving you a volume in cubic feet, then dividing by 6, to give you the cubic-feet-per-minute (cfm) required for a 10x turnover. The space required about 90cfm so I chose a 350 cfm shop fan and installed it over the sink area. It sucks air out of the shack so it will work well in controlling fumes coming from the wet process area. In order to relieve some forward-pressure on the shop fan I installed an input vent with tin ducting for light baffle. This will have a furnace filter on the end of it, keeping dust out of the darkroom. I chose a largely over-sized fan and I’m glad I did. When the door to the shack is open the air output from the fan is very strong. However, once the door’s closed it’s greatly reduced. I’m estimating I’m still getting at least 100cfm of air exchange, however.

Installing the fan’s frame in the window and cutting the surrounding wood for the interior was about an hour’s job and I finished that a couple days ago. The light baffle took about four hours to build all together, with the later stage of it a little rushed since it was quite dark at 11pm. There’s not a whole lot of work required on the shack, itself, now.

The logistics of water supply and the finicky job of fixing light leaks are the last tasks to complete. For the water I will probably build a rack that will hold a bucket with a gasket/pipe adapter drilled into its bottom. The same rack will have a holder closer to the floor that I can set the bucket on for filling without having to remove all the plumbing from it. I plan on hauling the water to the shack using 5 gallon pails with lids, loading 2-3 at a time on a 2-wheel dolly for transport from the house to the shack. Beyond gathering the plumbing parts and the task of cementing the piping, it shouldn’t be too difficult.

The light leaks will be tough around the door area because there isn’t a lot of space to build a second door, and frankly, I’d rather not go through the bother. I’m considering building a snap-on curtain system over the door made out of light-proof fabric, available on special order at most fabric stores. The vast majority of the light leaks will be solved with the ventilation system’s baffle but tonight I’ll be spending some time in the shack determining exactly where all the light leaks are happening.

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