View Full Version : Keeping constant temperature in darkroom

brian steinberger
4-Feb-2006, 22:01
I live in PA, and my darkroom is in my basement, so this time of year it is about 60 degrees down there. When I process my film I warm the solutions up to 68 degrees, but by the end of development they are usually a degree or two cooler. How important is constant temperature? Should I buy a karosine heater to warm my darkroom up to around 70 when I know I'm gonna be down there? That way the solutions won't cool during use. Same for printing. Thanks

5-Feb-2006, 01:23
yep keeping your darkroom at a constant temp is the ideal solution. You can then keep a resevoir of water in the darkroom so that its always at "Room temperature" which is the same as developing temperature. Problem is that this is usually not practical for reasons of cost and wastage of electricity and in the summer you'll be needing to cool the darkroom rather than heat it.

Oil filled radiators are definitely a better option than kerosene burner.

Ted Harris
5-Feb-2006, 07:12
You can also focus on just keeping your water temperature where you want it and not worry about heating the darkroom. A water temperature control panel/mixing valve setup will do that for you. There are simple solutions that cost less than $50 and are not too reliable and they go up into the hundreds but used ones in good condition are frequently available on eBay for little money. I just checked and there are three there right now that will likely sell for well under $100.

Matt Miller
5-Feb-2006, 09:27
Like Dan, I use an oil filled electric heater. I place it under the sink to keep the sink surface at around 72 degrees. If you develop by inspection you won't have to be constantly concerned with small changes in temperature.

eric mac
5-Feb-2006, 10:58
My darkroom hits the upper 40's (like right now) in the winter. I don't have enough heat from those small heaters for the room. If I am lucky I get up to the mid 50's. I ended up using an aquarium heater in each tray to keep the chemistry at a balmy 70 degrees. I used a 50 watt heater rated for salt water, so I think they should be ok.

Don't forget the GFIC circuit to protect yourself.


5-Feb-2006, 12:20
i always worked on temperature control one solution at a time. my darkrooms have always been low tech with temperature swings from the 60s to the 90s, but it's never been a problem to keep solutions within half a degree.

i start out with everything at 68. i do this with a bucket of water--hot water in the winter, ice water in the summer. i temper the solutions by pouring into an old stainless nikor tank that i immerse in the bucket with a thermometer, and stir until it's about right. i then decant into a plastic graduate, and set that in a tray full of water. not 68 degree water, but hot water if it's winter, and cold if it's summer. this helps hold it around the right temp.

then, right before use (i'm using a jobo tank on a motor base, so my hands are free and i can see), each solution revisits the tempering bath to get to the exact temperature. and yes, i rinse the nikor tank and stirring rod and thermometer when moving from one solution to the next.

my wash water i gather in half-gallon stainless jugs--there is enough thermal mass here that i can fill these at 68 degrees and they'll stay the right temp for the duration of processing.

it sounds like a lot of work, but once it's a routine you don't even have to think about it.

Howard Stein
5-Feb-2006, 17:48
For Black & White (I know of no current color process that runs at 68 F) what counts is the average temperature during the development process. Take the advice from the others and DO NOT use a kerosene in a darkroom. Any of the heating devices suggested earlier will work just fine. What might be of more importance is that you should not wash either negatives or prints in very cold water below (58F). The cold water shrinks the gelatin so tight that wash is not very effective.

5-Feb-2006, 19:31
i got anal about temperature consistency back when i was using mostly 35mm. i experimented with washing the negs in unregulated flowing water ... not sure what the range was, but it was on the warm side. all the resulting negs looked extra grainy to me. i didn't understand how this would be possible. someone suggested it could be a reticulation effect. all i know is that when i went back to controlling the wash temperature, the smooth grain returned.

Ed Richards
5-Feb-2006, 20:18
You can also save a lot of water you have to temper for washing by doing it in some fashion that lets you do a complete change of water. The efficiency of washing depends on the effectiveness of draining - if you do three washes but drain the tank carefully with each one, you can get a 95% water change each time and the final rinse will be 5% of 5% of 5%, which is pretty good. The amount of water does not need to be any more than the minimum necessary to cover the film.

Andrew O'Neill
5-Feb-2006, 20:28
Where the heck is PA?? The only PA I know is Prince Albert, Saskatchewan...

5-Feb-2006, 22:41
For $20-30 you can buy a submersible aquarium heater that will keep a tray at the right temp all night long. I bought a cylindrical 75 watt stainless submersible on sale for $12 a couple weeks ago. It sets partway in the groove in the bottom of an 11x14 tray of water around my 8x10 developing tray, and takes about 2.5-3 liters of water to cover it completely. I start it up 1-2 hours before beginning my session (my darkro0m drops to 50 or below when I'm not in there, I only heat it when I'm in there), or just fill the tray with 68-70 degree water if I'm in a hurry to start. It keeps my developer +/1 degree. Bigger trays or heating multiple trays with one heater may require a small circulating pump and bigger wattage, but this has worked perfectly for me for a couple weeks now.

Sal Santamaura
6-Feb-2006, 09:11
"Where the heck is PA?? The only PA I know is Prince Albert, Saskatchewan..."

For those without a US orientation, PA is the US Postal Service's official abbrebviation for Pennsylvania.