Too manly of a film dryer... a common problem?

[Jay Decker]

Purchased a used heated film drying cabinet. After cleaning it up and installing a new air filter, I used it to dry some 8x10 negatives. After run about 10 minutes, I opened the door with the fan still on to see how dry the negatives were. I saw that the film was really flapping in the air flow, two negatives had touched and stuck together, and the negatives were dry. Is this a common problem?

[ic-racer]

No fan, no heat. In my opinion that is the best way. I heat control strips so I can read them quickly.

[jeroldharter]

I think your negatives are too wimpy. Try stapling them back to back before putting them in the film dryer.

[Jay Decker]

No fan, no heat. In my opinion that is the best way. I heat control strips so I can read them quickly.

Please clarify two things:1) Are you saying that you think that the best way to dry negatives is with no fan or heat? 2) What are "control strips", how do you heat them, and what do you "read"?



I think your negatives are too wimpy.

Yes, that is the problem with my photography and "other" things... according to my wife.



Try stapling them back to back before putting them in the film dryer.

Great solution! Beats the hell out of my wimpy solution, i.e., partially covering the inlet to starve the air flow enough to eliminate the transonic wind tunnel characteristics.

[jeroldharter]

I don't think there is usually a hurry with LF negatives. Using air and heat introduce variables that offer little to improve quality. So I would not use either if you are having problems. I have a cabinet like that (Arkay) and I use the fan and heat for drying wet reels and Jobo drums, film testing negatives, etc. But I try not to use the fan/heat for regular negative processing.

[Jay Decker]

I don't think there is usually a hurry with LF negatives. Using air and heat introduce variables that offer little to improve quality. So I would not use either if you are having problems. I have a cabinet like that (Arkay) and I use the fan and heat for drying wet reels and Jobo drums, film testing negatives, etc. But I try not to use the fan/heat for regular negative processing.

Hmmm... I find it funny that you say that you don't try use the fan and heat for regular negative procession. With the exception of too much airflow the drying cabinet worked great - I had no dust on my negatives, which had been an issue previously, the negatives were where dry quickly, i.e., I can develop and scan in the same session, and they were protected by the cabinet while I did other tasks in the same room.

[Vaughn]

I use a film drying cabinet with a built in heater and fan. I turn it on several minutes to heat up (85 to 100F) before I load the 8x10 film into it . After loading, I do not turn the heat or fan back on and let the film dry over night. Opening the door to load the film dumps most of the hot air out of the cabinet, but the cabinet walls are still warm. There is some very slow air circulation in the drying cabinet for a little while as the warm air rises and is replaced with fresh air through the bottom of the cabinet.

But there have been times when I have needed to dry the negs fast and turned the heat and fan back on. No dust problems. I still don't turn it back on most times, and just leave them overnight. Usually because it is very late at night and I want to go home and get to bed...and it is so fun in the morning to pull the new negs out of the drier and onto a light table for a real good look!

Vaughn

[Keith Pitman]

Rheostat on the fan?

That said, I hang mine to dry in a humid darkroom and don't open the door again until I know they are done.

[Peter Mounier]

Please clarify two things: ...2) What are "control strips", how do you heat them, and what do you "read"?

Control strips are (film) factory made strips of film with color patches that you develop along with your film. The color patches are read with a densitometer to determine whether the development meets the factory specifications for proper development.

Peter

[jeroldharter]

Hmmm... I find it funny that you say that you don't try use the fan and heat for regular negative procession...

I use an air filter, low heat, adequate room to separate the negatives, etc. But every once in awhile I will have a dust spec or find that the negatives somehow crept too close together. It is just not worth it to get to that point and have an otherwise good negative ruined. So as much as I can tolerate it, I wait for the negs to dry without the fan. Heating up the cabinet a little before drying is a good idea.

I just re-did some BTZS tests and wanted to do the densitometer readings quickly so I dried those negatives with the heated fan. I did not care so much if they had any dust.

[Hovmod]

My wind tunnel is good for 4 strips of 120 if I space them properly and have clips to weigh them down.
Sometimes I put the fancy looking HP Combitank innards right in there, but singles go alone.

[domaz]

I just hang my negatives in a free-standing garment storage unit. No heat, no dust but it takes quite a while to dry that way- usually overnight.

[Brian C. Miller]

See if you can get a different fan for your unit. If it is a 12V fan, then you might be able to replace it with a low-speed Panaflow fan.

[John Koehrer]

A speed control for a router would work..Harbor Freight Tools.
or perhaps an air filter(automotive) between the fan & film?

[Michael Graves]

This has been an interesting post, as I have a California Steel drying cabinet that is a work of art...BUT...with the blower on, I need to keep good separation between negatives or they will stick together and I will blow up. So I understand the issue of too much hot air. What I DON'T understand is why hot air is considered manly. In my experience hot air generally comes from other directions.

[Jay Decker]

This has been an interesting post, as I have a California Steel drying cabinet that is a work of art...BUT...with the blower on, I need to keep good separation between negatives or they will stick together and I will blow up. So I understand the issue of too much hot air. What I DON'T understand is why hot air is considered manly. In my experience hot air generally comes from other directions.

I think we have the same drying cabinet. I have the Deluxe Drying Cabinet by California Stainless Mfg. Have you tried partially blocking the inlet to reduce the air flow?

[John Koehrer]

By blocking the inlet, the motor may overheat & die. A cooling fan from a computer may work it's 5V.

[Harold_4074]

Blocking the inlet will only kill the motor if it is overloaded and relying on the airflow for cooling.

Reducing the airflow without decreasing the heat input will raise the temperature of the air leaving the heaters, and possibly burn them out prematurely. This is true even if there is a thermostat to control the average temperature in the cabinet. Without a thermostat, you are really asking for trouble.

If there are two independent heaters, you may be able to wire them in series rather than in parallel; this will drop the heater power by a factor of four, allowing you to decrease the airflow by that amount with no risk. Alternatively, wiring a dimmer control into the heater circuit will let you drop the power gracefully.

But don't try to run the motor on reduced voltage unless you really understand what you are doing; not all motor types take kindly to this.

[Kevin Crisp]

I am just surprised so many are using film drying cabinets. (I am not being critical, just surprised.) I have a couple of those retractable (hotel bathroom style) clothes lines on a darkroom wall. I pull them out and put the negatives on there with clothes pins. It takes about an hour for them to dry. Dust is not a problem if I turn on the HEPA filter when I start developing the film.

The last time I used a cabinet was on the school paper, and then only when I had a very short deadline.

[ic-racer]

Please clarify two things:1) Are you saying that you think that the best way to dry negatives is with no fan or heat? 2) What are "control strips", how do you heat them, and what do you "read"?


To elaborate. In 1973 I got the Fred Picker book and he said not to use heat for negatives. Right or wrong, since then I just air dried with no problem. Below is my current setup. Of note I have a controlled 50% environment that I monitor with a sling psychrometer.

The control strips are short pieces of film exposed to a step wedge. I'm usually anxious to get them on the densitometer right away so I use a blow drier. (the slope of the curve determines my development time) The emulsion surface frequently looks mottled in reflection, but it doesn't seem to affect the results. Thought I'd not want my good negatives to look like that.

In my own opinion a proper drying area is so important, when I built this current darkroom, I did not process any film until the drying cabinet was in place.

http://img.photobucket.com/albums/v670/ic-racer/DryingCabinet.jpg

[Jay Decker]

By blocking the inlet, the motor may overheat & die. A cooling fan from a computer may work it's 5V.


Don't mean to geek out too much, but from a thermodynamic engineering point of view, a fan is a constant-volume device since it delivers the same air volume regardless of the air density. Partially blocking the inlet side of the fan results in a decrease the air density on the inlet side of the fan. Since the fan is moving the same volumetric amount of air, but with the inlet partially blocked the air is less dense, so the mass of air moved to the discharge side of the fan is less. So, the correct way to mechanically throttle a fan, or any other constant-volume device like centrifugal blower, is to throttle (valve) the inlet. There are limits as to how much you can throttle a fan, i.e., where vibration due to surging or motor heat from low air flow can create mechanical failures. (An engineering education does terrible things to your brain.)

I was wondering if anyone had tried throttling the inlet side of the fan.

[Robert Hall]

Omg, Jay! Serious geeky-ness. :)

How about putting a dimmer switch on the motor?

[Harold_4074]

Omg, Jay! Serious geeky-ness.

Oh, come on. What's wrong with geeky-ness? He didn't even mention positive and negative fan characteristics, or the fact that axial fans have both near-field and far-field characteristics!

As for dimmer-switching the motor, make sure that you understand back EMF and impedance before trying this......

(Maybe there should be a forum for the engineering and thermodynamics of photography?)

[Jay Decker]

Omg, Jay! Serious geeky-ness. :)

How about putting a dimmer switch on the motor?

This gets really geeky... most dimmer switches are silicon-controlled rectifier (SCR) type electronic devices, which are great for things like incandescent lights, heating elements, or other resistive load devices, but are bad electric motors, fluorescent lights, or other inductive load devices. So, the bottom line is that you don't want to use a wall dimmer switch as a speed controller for an electric motor. However, you could use a variable frequency drive (VFD), which is more expensive for small motors, or an autotransformer, commonly known as a "Variac", which is more affordable for small motors.

[Harold_4074]

And it gets even worse: a universal-wound motor (as found on tools like woodworking routers) will tolerate voltage reduction reasonably well, but induction motors need the back EMF developed at speed to keep the winding current reasonable. Operating one of these in brownout conditions is a good way to fry it...

Is there any way to get this discussion back to something resembling photography? :)

[Jack Dahlgren]

And it gets even worse: a universal-wound motor (as found on tools like woodworking routers) will tolerate voltage reduction reasonably well, but induction motors need the back EMF developed at speed to keep the winding current reasonable. Operating one of these in brownout conditions is a good way to fry it...

Is there any way to get this discussion back to something resembling photography? :)

Hmmm....

I had a wall plug which was on a dimmer (lights were plugged into it) but someone decided to plug the vacuum cleaner into it and it fried the vacuum circuit board - too much current. I resoldered the board and replaced the switch.

This reduced the number of dust spots on my negatives.

[jp]

opening up the door with the fan on could really screw up aerodynamics. It'd be sort of like opening your car windows while driving fast and wondering why things were blowing all around.

If it's indeed too violent a wind in there, I'd use a computer case fan. They are available in a bunch of sizes that can be surprisingly big - 8" or so. They run off 12vdc which would be easy to power, and often have a speed adjustment attached, as many computer users like big slow fans instead of small fast fans for sound quality reasons.

[Robert Hall]

Is there any way to get this discussion back to something resembling photography? :)


For anyone with a functioning darkroom, this IS photography.

Long gone are the days of hopping down to the photo store to pull the solution off the shelf.

Ugh, those were the days.

[Harold_4074]

This reduced the number of dust spots on my negatives.

Good work, Jack. I thought that I was going to have to ask for advice on film choice, f/stop and developer for photographing the smoke from a burning fan motor :)


For anyone with a functioning darkroom, this IS photography.

Can't argue with that. For art to happen, there pretty much has to be craft.

One of the best arguments for forums like this one is that for most people, along with the vanishing of neighborhood "photo shops" there is the disappearance of friends and acquaintances who can shed light on things mechanical and electrical. Unfortunately, asking us geeks and nerds can at times be like trying to get a drink of water from an open fire hydrant.

Incidentally, I mis-stated the effects of rewiring two heaters in series: the power dissipated by each heater drops by four, but there are two of them, so the total power only decreases by a factor of two. Still the concept is sound and may keep the heaters from burning out if you reduce the airflow. The best solution is a dimmer for the heater circuit, plus a fan with a smaller output when running at full speed. At some point, too small an airflow will fail to remove water as fast as it can evaporate from the film, and you don't want to steam-cure your emulsion...

[Michael Graves]

I think we have the same drying cabinet. I have the Deluxe Drying Cabinet by California Stainless Mfg. Have you tried partially blocking the inlet to reduce the air flow?

Nope. But I'm going to this weekend.

[Jay Drew]

ic-racer
I had to laugh when I noticed your film hangers.
Are you a surgeon?
Actually not a bad idea, JD

[Pawlowski6132]

I just hang my negatives in a free-standing garment storage unit. No heat, no dust but it takes quite a while to dry that way- usually overnight.

I also use a free-standing garment storage unit. But, in the bottom of mine I have a good size air cleaner. It keeps the garment unit dust free and circulates the air to help drying. This winter, I may put a very small heater in their too.

[pedrosal]

I wanted to speed up drying time on some test film and put it in a pre-warmed oven. I found the film fit exactly with the top only just balancing against the grid and the bottom resting on the tray (careful with accumulation of water there).
Result: quick-drying, no holder/peg marks and NO dust!