D.I.Y. Roll Film Dryer

Sorry I did not take more photos as I was building this home made film drying rig, but it's pretty simple.

The black rectangle on the right side is an air filter held in place with blue tape.

Under the filter are two fans, side-by-side, pulling filtered air into the box. The fans are like the ones that cool electronic equipment, but these are bigger and more powerful than a typical computer fan. I got them at Radio Shack for another project (now de-commisioned).

Inside the box is a light fixture which holds an incandescent light bulb, for heat. The light bulb is not directly under the chimney because I do not want water dripping down on a hot bulb.

The film, still on the spiral reels, goes into the white plastic chimney (PVC pipe). A grate is needed (shower drain) to keep the reels from falling into the box. I made the chimney tall enough for 4 reels of 135 - more than enough for my needs. Tip: don't glue the chimney pipe to the flanged base. With the chimney pipe removed, I can replace the light bulb without needing to unscrew one end of the box.

Using a 100 W light bulb, the outflow air is heated from 72* F to about 78* F, but it takes a while.

Using a 150 W light bulb, the outflow air got up to 87* F

I briefly tested a 250 W bulb which got up to at least 89* F - it was still climbing when I stopped testing. The outside of the box was getting warmer than I liked, so I’m thinking a 250W bulb is too much for this rig.

So far, I have dried only 2 rolls - both at the same time. Using a 150W bulb, the film was definitely dry after 1-1/2 hours - possibly much sooner. I watched a movie while the film dried and did not check them until the movie was over. Once I know about how long it usually takes, I plan to replace the ON/OFF switch with a timer switch, so I can't accidentally leave it on.

Obviously, putting a hot bulb inside a small wooden box is not without some risk. Take care not to end up on the evening news, sobbing in front of the smoldering ruins of your house.

Fun, I like the toggle switch. Plug it in to a Gra-Lab timer if you have one. I am not sure you even need the bulb. Also if the fans would quit it would be a very warm Eazy Bake oven. Looks good!

Apart from time, is there any advantage to heating the drier?

John51 said:

Apart from time, is there any advantage to heating the drier?

Click to expand...

The only reason I warm the air is to reduce the drying time. The sooner the film is dry the sooner it is safe from dust sticking. I tried hanging my first roll in the shower but that took several hours. Here in the Midwest / upper south summers can be very humid. Heating the air lowers the relative humidity which makes drying much more efficient.

There was a commercial version of this. Perhaps by Kindermann; not sure. A small plastic box that held 2 35mm or 1 120 and a small fan. No heat think.

In your case, I think you might find the heat and the 2 fans overkill unless you really need very fast drying or are in very humid conditions. By drying with filtered forced air, you should be able to avoid the dust sticking even with a longer drying time.

What material did you use for filtering?

mshchem said:

Fun, I like the toggle switch. Plug it in to a Gra-Lab timer if you have one. I am not sure you even need the bulb. Also if the fans would quit it would be a very warm Eazy Bake oven. Looks good!

Click to expand...

Would have to get a look at the wiring to judge risk, but the odds of having two fans fail in a case where the light stays on seems rather low. If you wanted to get really paranoid I guess you could rig some kind of airflow detector to control the light [Light can't come on unless flow is detected], and possibly a thermal safety switch while you're at it.

But personally I would be tempted to replace one side with plexiglass and hang a ribbon over the fans, then leave the box somewhere I'll be likely to notice a fault.

There's a tradeoff between heat and airflow. The faster the flow of air, the greater a heat source needed to result in the same air temp at the film. I'd opt for reducing the airflow and no more than a 60w bulb in that size wooden enclosure. I'd be tempted to drill a tiny hole in which to insert a probe thermometer - at least for testing.

mgb74 said:

[...]

What material did you use for filtering?

Click to expand...

I already had the fans, plywood, lamp socket, and switch - and the plumbing parts were a no brainer - so the filter was the last factor I needed to sort out before sketching dimensions. Wandering the isles of a local home building store I discovered <these filters> made for a Honeywell air purifier. I had high hopes for the "HEPA" filtration - but my little fans did not have enough power to pull a good airflow through the HEPA accordian filter. However, the HEPA filters I bought had a pre-filter - a black mat material, probably carbon inpregnated for odor control. So I peeled the prefilter out of the HEPA cartridge and just used that. The pre-filters are available separately, something like <this> Had I known, could have saved some money. Good airflow, but filtering efficiency is unknown. The carbon part is unnecessary, and there are probably dozens of better options for this application, but that was the starting point for this project. To repeat, I am sure there is a better option - some kind of filter material in a roll or sheet that will not bog down the fan, but which will still catch all visible dust.

mgb74 said:

There was a commercial version of this. [...]

Click to expand...

I took a medium format photography class last spring, and the university photo lab does have a commercial film drier that works similar to mine. We dried our medium format film by hanging it in a film drying cabinet; takes about 15 minutes. The film photo 1 students used the "hair drier" for their 35mm film, and it was fast - less than 10 minutes. I didn't notice the brand, but as I recall it was all metal, and it put out a great deal of very warm air. Mine is tame in comparison.

For 40 years I've just let film hang to dry. I picked up a beautiful film drying cabinet a couple years back from a shop closing, it works great. The only time I use it is when friends are waiting. Old habit for me, I do use a dehumidifier in my darkroom.
Your design has been used in various configurations for decades. Looks like it will work fine.
Plus, free parts are great!

Very clever, great work.

Hi! I was wondering if there were any updates on this? Has it been working well? If it has, would it be possible to see some more pictures of the unit/its design please? I'm planning on developing my own film but would much rather dry film as a roll rather than hanging it somewhere!

I like to hint at the safety issue. In such cases of small wooden boxes, without airrtream in case the blower fails, one might consider a thermofuse.

Is it a good idea to dry on spirals?

Helge said:

Is it a good idea to dry on spirals?

Click to expand...

When done carefully, and not over-heated, and if you are tolerant of the possibility of a bit more curl, it works well.

MattKing said:

When done carefully, and not over-heated, and if you are tolerant of the possibility of a bit more curl, it works well.

Click to expand...

The few times I tried it, I experienced “caking” or spots of photo flow residue around the touch point, often reaching into the image part.

Helge said:

The few times I tried it, I experienced “caking” or spots of photo flow residue around the touch point, often reaching into the image part.

Click to expand...

That usually means you have hard water, your Photo-flo concentration was too high, or both.
I think most of the on-reel dryers were designed for steel reels, so the reel type may matter.

MattKing said:

That usually means you have hard water, your Photo-flo concentration was too high, or both.
I think most of the on-reel dryers were designed for steel reels, so the reel type may matter.

Click to expand...

Both probably. Actually I use Adostab now. Works very well.

The old Honeywell KleenDri I use recirculates the air, but forces it through a canister of silica gel crystals. It takes about 50 minutes to dry a film, and I place the metal canister in a toaster oven at 150ºF fro 20 minutes afterwards, and store it in a ziplock bag until the next time I process a film. It holds a single 35 or 120 reel (Paterson or metal, or a Rondinax 60 reel - the Rondinax 35 reels are to big and I carefully re-spool the wet film onto a metal reel to dry it). I took it appart to resolder some poor connections inside, and it has no heat source other than the fan motor itself, but since the air recirculates it gets nice and warm in there. I hand the films for ten minutes with a heavy bulldog clip on the bottom and they are usually flat enough to scan without a struggle. I like your design and would make something similar if the Honeywell ever packs in.

mtapics said:

Hi! I was wondering if there were any updates on this? Has it been working well? If it has, would it be possible to see some more pictures of the unit/its design please? I'm planning on developing my own film but would much rather dry film as a roll rather than hanging it somewhere!

Click to expand...

I have dried about a dozen rolls of 35mm film so far, and I think it is working well. But the more I think about fire safety, the less I like the light bulb, so I suggest skipping that part. If it takes a little longer, I can wait.

If I wanted to make another one, and did not already have the fans, I would consider trying to eliminate the wooden box and the light bulb. That is, I would try to add a fan to the top of a PVC pipe pulling air up, and a filter to the bottom of the pipe for the incoming air.

Could the bulb be in its own external chamber, heating air that would then flow or rise into the film chamber?

I used to hang film from some pipes in my workroom and one day I realized I could jam a small fan above the pipes. The added airflow cut down drying to about 45 minutes (low humidity to begin with) but there weren't any issues with having the airflow in the open as opposed to in a cabinet as long as you use lead clips as weight, which help with flatness. One day the fan quit and I never bothered replacing it, I still get my film dried in 1-1.5 hours just hanging in low humidity, which at the moment is 2%, thanks to the HVAC in this building...no wonder my lips are cracked.

MattKing said:

That usually means you have hard water, your Photo-flo concentration was too high, or both.
I think most of the on-reel dryers were designed for steel reels, so the reel type may matter.

Click to expand...

I've found photoflo to be problematic when used in tanks with film on reels. It seemed I could never get the residue out of the tanks or off the reels and it would build up over time. I switched to hanging the film first then running a bead of water down both sides of the film using half the recommended photoflo concentration in a squeeze bottle. After I started doing that I never had trouble with spots, foam, dust. Also, the best method IMHO is to substitute photoflo water for DI or distilled water. I find both works just as well as photoflow.

runswithsizzers said:

I have dried about a dozen rolls of 35mm film so far, and I think it is working well. But the more I think about fire safety, the less I like the light bulb, so I suggest skipping that part. If it takes a little longer, I can wait.

If I wanted to make another one, and did not already have the fans, I would consider trying to eliminate the wooden box and the light bulb. That is, I would try to add a fan to the top of a PVC pipe pulling air up, and a filter to the bottom of the pipe for the incoming air.

Click to expand...

You might also try using a hairdryer on cold and work on the reel from both sides. That removes the vast majority of water very quickly, leaving only the emulsion bound water to evaporate.

If you desperately need the film dry very fast you can substitute the last wash bath with pure alcohol and give it a real good shake. Then hang to dry. You can reuse the alcohol several times.
Drying time is a matter of minutes then.

Update, 12/28/23. As a safety consideration, I replaced the on/off toggle switch with a 15 minute rotary timer switch. After the switch goes off (15 minutes), my roll of film is almost dry. After removing my film from the spiraI reel(s), I usually hang the it with a weight for a little while before I cut the strips to length and put them in PrintFile sleeves.

That was a year ago, and since then I have dried another 12-15 rolls without problems.