DIY Film Drying Cabinet

My current film developing station is housed in an unfinished part of my basement. I have ample counterspace, storage for chemicals and developing equipment and plenty of room for activities. I even have a large utility sink with running water. But my space also has dust. And this wreaks havoc on film that’s hanging to dry!

Dust on negatives shows up as little white spots on the images after the negatives are scanned (or printed). And this can create the need for a lot of post-production work to get rid of those spots. My scanner software is smart enough to recognize dust and eliminate it…but only on color film. And since the majority of my scans are black and white negatives, the software isn’t much help to me. Dust on negatives is a neverending battle and I’m not aware of any means of eliminating it all together. But it can be mitigated.

Without going into all the ways of reducing dust in your drying area, one way is to utilize a drying cabinet. But they’re expensive! When I researched them, they started out at several hundred dollars. Some topped $1K.

*This is just one of the many options for commercially produced film drying cabinets.*

Since I’m thrifty, I set out to design and make my own. I started by looking on Facebook Marketplace for suitable cabinets for my project. The issue I ran into was that most of the cabinets I found weren’t tall enough. A roll of 36 exposure film is almost 5 1/2 feet long. Granted, most of the film I shoot is bulk loaded and the rolls are much shorter than commercially produced ones. But, I do shoot packaged 36 exposure rolls from time to time, so my cabinet has to accomodate them.

Eventually I found an old gun cabinet for sale. It had a glass front which I liked. This would make it super easy to ~~know~~ remember if film was loaded or not. The sellers were moving and desperate to get rid of it. I talked them down to $35 and brought it home.

Once it was home, I measured the interior space from top to bottom. The “bottom” was actually the top of a lower storage compartment. This compartment has a keyed, fold down door. The interior height of the main compartment was not quite tall enough to meet my required specs. So I tore the thing apart, removed the “top” of the storage compartment and enlisted my neighbor to help me make some strategic cuts with his table saw. We essentially cut out the center of the board while retaining the frame and outside “ledge” which sits under the door.

*The area marked in blue at the bottom was removed to make the interior height usable for my purposes. The center gun rack was also removed.*

After making the cuts, I replaced the modified part and reassembled the cabinet. My modifications opened up the inside height nicely. The added room made the overall height just perfect. I also tore out the center gun holders. I patched a few small holes because it was important to make the interior air-tight. I added weather seal around the door frame and also to the keyed door for the lower compartment.

Weather seal was added to the door to help make the interior *air-tight.*

I didn’t want the cabinet to simply be a static, air-tight compartment. I wanted moving air to speed up the drying and to promote uniform drying. I tapped into ChatGPT and it was suggested to me that adding a fan at the top and a HEPA filter at the bottom would do the trick. The idea was that the fan would blow air out of the cabinet. This would create negative pressure which would draw air through the filter and back into the cabinet. This filtered (and dust-free) air would be pulled up and over the film then out the back through the fan again.

I went on Amazon and bought a pack of 86889 HEPA filters. I also bought a 120mm CPU fan. This is the same kind of fan you might install into a computer project.

Once these parts arrvied, I had no actual way to install/mount them to the cabinet. I’d have to cut holes through the back of the cabinet to accomodate them, but you can’t just stick a filter in a rectangular hole and expect it to stay there. Same for the fan. So I designed the mounting parts myself. I have a 3D printer and some rudimentary CAD skills.

I designed a simple box of the exact dimensions of the HEPA filter. I made the bottom of the box a honeycomb grid to allow air flow. The box included tabs on either side with small holes to accomdate M4 mounting bolts. The box also included two cut-out semi circles for fingertips to allow the quick removal/changing of the filter as needed. The top of the box is also a honeycomb grid and snaps into place which secures the filter.

I designed a backing plate with holes to match the holes on the HEAP box. I cut a hole in the back of the cabinet the same size as the filter (and same size as the opening of the backing plate. The backing plate mounts on the back exterior of the cabinet and aligns to the HEPA filter box which mounts on the inside back of the cabinet. I added thin weather stripping betweent the cabinet panel and the 3D mounting parts to further insure no dust entry points.

*This is the inside (and bottom) of the cabinet and a view of the filter mounted.*

*This shows how the top of the filter box is removeable to allow for the changing of the filter from time to time.*

Then I designed a mounting plate (and accompanying backing plate) for the 120mm fan. These were used to mount the fan at the top and back of the cabinet. The fan was mounted to blow outward, which draws air out of the cabinet.

*This is the fan after it was mounted inside the cabinet. Notice the M4 bolts I used to go through the back cabinet panel to mate with the backing plate which mounts on the exterior.*

*I bought a small wooden dowel and cut it to the width of the inside of the cabinet. I 3D printed mounting brackets for the dowel (one on each side) to mount the rod across the width of the cabinet.*

I 3D printed these film clips and attached them to the wooden dowel with a black zip ties, which were trimmed of their excess. I didn’t design these clips. I found them online. The film slips directly into the clips and which hold them tight at the top of the cabinet. Another clip is used at the bottom of the film for a litte weight and to hold the film straight.

The fold down door on the bottom of the cabinet can open up to accomodate this plastic lid I put on the botoom to catch any water drips from the drying film. When film drying is in progress, the door is closed. The weather stripping helps keep dust out and promotes the air flow cycle caused by the fan and filter.

*I created a light sign that sits on top of the cabinet. It illuminates whenever the cabinet is in use.*

I installed an interior strip light around the perimiter of the cabinet. Whenever I say, “Hey Google, turn on the film drying cabinet” the fan, interior light and lighted sign all kick on in unison.

*Here’s a peek at my basement Hobby Room, complete with a working Film Drying Cabinet.*

But, does it work? I’ll let you be the judge. Below are a few shots from the first roll of film I dried using my film drying cabinet. They required zero post-processing.