Butane

[Athiril]

surround the developing tank/trays in a water bath in a large enough home made tank + $10 aquarium heater.

[benOM]

I use the bottom part of a 205 ltr plastic barrel (free) with a 1Kw Immersion heater element fitted into the side (very cheap), It's big enough to float trays in and bottles of chems and easily goes hot enough for doing colour. I use a fish pond pump to circulate the water to keep it even, It also doubles up as a handy film washer!

[Bob_]

I had similar results in a cold college darkroom some years ago. We gave up that session and no useful prints were made. We all had pullovers and coats on and were still cold.
If my memory is correct metol stops working at about 14C. knocking out half of the developer (I cannot recall what we were using). It slows down rapidly until it stops too.

Robert

[travelingman]

If I remember from chemistry practicals, simple chemical reactions by and large proceed at a speed governed by temperature, so increasing your development time by a factor per degree below 20 degrees should bring you to the right degree of development. Since installing a new efficient boiler my cellar darkroom temperature has dropped from around 20 degrees to 16 degrees and I have arbitritarily increased dev and fix times by 25 per cent. Seems to work. Any chemists out there can help?
Richard

Correct. The lower the temperature, the slower the particles start to move. Getting into how reactions actually work, the most important factors are how hard/how fast the molecules collide with each other and how often. Reactions between molecules have to collide with each other in a certain way in order to make new solutions. So once the temperature gets to a certain point, the speed is reduced to such a point that the molecules won't collide with enough force, thus no visible reaction occurs.

Basically, thats what happens.I could be partially wrong, please anyone feel free to correct me.

[fschifano]

I use a torpedo heater for the garage & it uses kerosene fuel, I think that's what you folk call paraffin.
Kerosene heaters come in a variety of sizes. the torpedo has a fan that moves a lot of air, but there are units that are about 18-24" tall X 10-12" diameter without a fan that work very well. Usually they have handles to move them around with & are not heavy. There may be a visible orange glow with them though. It is orange & MAY be safe around paper. Definitely not film.

No, you don't want to use one of those things. They stink and emit filthy exhaust gasses. You'll get yourself sick or worse running one of those things in a closed room. Spent some time in a garage with one of those thing running once. Had a splitting headache within 15 minutes, and had to get out of there. Freezing my ass off was more comfortable.