Maintaining 68F ????

[hortense]

What this means in a practical sense is that over the temperature range of 20ºC thru 25ºC I can use a time adjustment factor of 9% per ºC ...
http://www.shodor.org/unchem/advanced/kin/arrhenius.html#ea

For those of you that get cross-eyes looking at the time/temp curves, here is an easier chart. I 'll try to figure out how to attach it.
MAC

 

[hortense]

Time/Temp Chart Available

For those of you that get cross-eyes looking at the time/temp curves, here is an easier chart. I 'll try to figure out how to attach it.
MAC

I'll be happy to pm or e-mail this chart to anyone that asks for it.

 

[waynecrider]

I have the opposite problem: in the winter my basement darkroom, which happens to have 3 outside walls, radiates lots of cool air off the walls and chills my paper solutions. I am interested in the "radiant barrier" referenced by waynecrider. Does he, or anyone else for that matter, have more info?
Thanks!

Well a google search of radiant barrier will turn up in the first page about as much as you need to know. For you it would be used to prevent heat loss; For heat gain uses it's used in the attic. All it is is 99% pure aluminum foil facing an open air space. It would normally be attached to the trusses in the attic for heat gain. It also comes on sheet plywood for the roof. I'm sure after you read some threads you can figure out how to use it for your application.

 

[Ronald Moravec]

Once you have a tray stabilized at 68 or wharever, put it on an unsidedown tray or piece of styrofoam to minimise heat transfer to the sink or countertop.

Apply sheets of foam insulation to the walls of the basement with liquid nails. cover with masonite. My walls no longer feel the slightest bit cool no matter how cold it gets, and it gets below zero here.

 

[Maine-iac]

Any suggestions other than a water bath or air conditioner to maintain 68F in a room with ambient air at 80F? I've read processing at this temperature isn't wise. I want to run some tests with a slosher for up to 40 minutes. I ran a temp test using water... the temp increased 3 degrees F in just 8 minutes!

A waterbath sloshes around and moves the developer tray too much. (I'm of course using minimal agitation) I don't have a dedicated air conditioner for the room.

Any suggestions?

I had the same problem in Malaysia years ago. Couldn't keep the ambient temp under 80 even with an air conditioner. Couldn't get the ambient water temp under 85.

I discovered Divided Development and have been using it ever since (no longer with film, but still with paper.) Check out the Divided D-23 formula in another thread in this forum.) D-76 can also be divided by separating the borax out into Bath B. Give it three minutes or so in each bath. Time is not critical.

I still use it for paper, and would never switch back to single-solution developer. Any developer formula can be divided by separating out the alkaline activator from everything else. With D-72 or Ansco 125 (Dektol equivalents), no time/temp controls are necessary. Roughly it takes about 15 seconds in Bath A to absorb the amount of developing agent the latent image needs. In Bath B (activator), you can leave it all day, and once it develops to completion it will not go farther. Only what was absorbed in Bath A can be activated in Bath B. Most any ambient temp will do. In colder darkrooms (60-65), it make take 30 seconds longer in Bath B to finish, or in warmer ones like yours, it'll be done in under a minute.

I've got a longer article and some formulas in the chemistry recipe section of this forum, if you care to check it out.

Larry

 

[Lee L]

There is also a form of double sided radiant barrier combined with foam insulation. Two US brand names are R-Max and Thermax. This consists of an aluminum foil reflectance sheet on each side of stiff insulating foam of varying thicknesses, commonly between 1/2 inch and 1 inch. It's available at lumber yards and home centers in 4x8 foot sheets. I've used it on wooden frames to black out large windows for darkroom space.

It would also work well in the applications Ronald Moravec mentions, both on the walls and under the tempering bath. If it's too much larger than the tray, the aluminum foil on top might dissipate some heat, but if properly sized, should work well.

Lee

 

[Gerald Koch]

Modern emulsions are better hardened than those of the past and will tolerate higher temperatures. I believe that Kodak now recommends 75 F for their B&W films. This temperature will be easier to obtain than 68 F against an ambient temperature to 80 F.