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Methods to dry hand processed film - looking for air knife recommendations


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I’m slowly improving my hand processing using a lomo tank, but the one thing that’s still visible are occasional water marks. 
also, hanging up to dry takes days. 

Does anyone have any suggestions? 
I’m doing the final rinse using distilled water with Kodak photoflo, but they still appear. My solutions are also made with distilled water. But I do rinse the film between steps with tap water. (Maybe this is bad?)

I was thinking about making the tail end of a processing machine, the dryer. 
 

I was thinking about an acrylic enclosure with the standard long racks to transport the film within the cabinet, keeping it in the warm air for around 7 mins or so. I’m not processing much, only 100ft at max, so I could probably pull it into the enclosure with some leader already laced up, and once all the film was in the enclosure, it could move dead slowly within just to avoid sitting on the rollers for too long
 

before entering the enclosure, I wanted to add an air knife to shoot off the water, particularly what’s held around the sprocket holes. This is always the source of water marks for me… I use some squeegee tongs, but water hides in the sprockets and then creeps out. 
 

I was wondering if anyone had any recommendations for off the shelf air knives they’ve seen used in film processors? I have a nice quiet Chicago air compressor here i can hook it up to. 
 

Also, if you think my idea is way too over the top, and I should just buy a hanging film heater. You can say that too… I’m just a bit over excited to make things.

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How precise are you with the amount of Photoflo you are using?  I have found even a tiny bit more than required can cause the very problem you are attempting to avoid.

Have you tried reducing the total amount of Photoflo being used? Try cutting the amount by 5 to 10% from suggested mix ratios and see what happens.

As for an air knife, we used to use a custom built air knife on our Triese machines, but switched to a vacuum squeegee. 

(From memory) The air knife relied on a pair of delrin rollers that floated in machined grooves inside a plexiglass box that was slotted on the top and bottom for film passage and supplied with filtered compressed air that blew from the top-down and blew the water out of the bottom back into the final rinse tank.   However, we found processing staples (probably not an issue for you) would eventually scar the surface of the rollers and cause marking on the film.  The rollers could also bind in the slots and scratch the film, so you had to watch them like a hawk during a processing run to avoid disaster.

Our current vacuum knife is also a custom made device, but it's pretty simple and effective.  If it malfunctions, it only leaves water spots and doesn't damage the film itself, so that's an improvement.  The film can be rewashed/reprocessed and the spots go away... 

There is a short cylinder oriented 90 degrees to the direction of the film transport that is attached to a back plate with two guide rollers above and below the cylinder.  These rollers guide the film through slots cut out on the top and the bottom (sides actually) of the cylinder to avoid rubbing against the lip of the slots.  The upper slot has two soft squeegees that barely touch the film surface, front and back (base and emulsion). 

At the rear of the cylinder, a PVC pipe passes through the back plate into the cylinder and is attached to a industrial grade vacuum system.  The vacuum sucks the water out as the squeegees gently wipe the film surface.

I could see it being replicated on a smaller scale with a small wet/dry vac to replace the industrial vacuum system for limited runs of film.  You might have to rig a bypass valve on the suction side of the shop vac to adjust the strength of the vacuum (just a "T"  with a valve open to the atmosphere) but it should work.

I can try to take pictures of the vacuum squeegee we use next week and post them here if you think it would help. 

I am doing this all from memory, away from the machine, so a picture might be more accurate.

 

Edited by Frank Wylie
clarification
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For air knives you want to use a Ring Compressor for either positive pressure or vacuum. Regular air compressors have too much pressure and not enough volume a Ring Compressor will deliver constant pressure or vacuum.

We have both the type of air knife Frank described on all the processors and also a type which has two pointed apparatus that have a slit for pressurized air to push liquid away from the direction of film travel into the tank the liquid came from.

 

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