cold temperatures in dark room

[Fred Braakman]

Hi,
I have the problem of my darkroom always being cool, around 17 to 18 degrees Centigrade. (Desired temp = 20 degrees) For printing purposes, is any temperature compensation required? I seem to be able to obtain decent prints at this temperature, but if the temperature rises to above 20, and I want to make more of the same prints, will that increase affect the print development that much?

Thanks.

Fred

[Alexey Shadrin]

Optical printing or digital?

[paulr]

It may or may not be an issue. If things get below 12 or 13 degrees celsius, hydroquinone becomes almost inactive, so you'll see a severe performance change in any developer that uses it.

But in general, developer activity is fairly linear with regard to temperature. The lower the temp, the more time to develop. I find that it's only important to be precise about this if you're using toners that are sensitive to the degree of development of the paper. Otherwise, in my experience, changes of plus or minus 20% or so aren't significant.

There are two basic approaches to control: either control the temperature (with a water bath, etc.), or else just monitor the temperature and adjust the time. I find the latter to be much easier, assuming things don't get much too cold.

A principle to use it that the emergence time of the paper (the time it takes for the image to first appear in the dark shadows) is directly proportional to the total development time. So if at 20 degrees celsius, your normal development time is 3 minutes, and the emergence time is 20 seconds, you know that for this paper/developer combination the ratio is 9 to 1. Then on a cold day, if the emergence time is 30 seconds, you just have to multiply by 9 to find your total development time (4-1/2 minutes).

[Fred Braakman]

Thanks Paul,
Is the emergence time also relative to developer depletion?

Fred

[bob carnie]

Fred

My darkroom is cold as well, and I have been looking for options.
This will sound wierd but on APUG last year a thread was started about using a Pig Warmer under your trays. Basically a waterproof warming blanket that is used to keep pigs warm in very cold weather.
Apparently they are very long and narrow and I am considering the use of one of these warmers under my trays. Set the temp and go all day.

Bob

[eric mac]

My darkroom gets to the low 50's F in the winter. I have a small heater to keep the buns warm, but the chemistry is in the 50's as well. I started using a small aquarium heater in each of the 3 trays. These are rated for salt water and are stainless steel. They have a seperate temp probe and it stays around 70 F.

Make sure to use a GFCI receptacle or circuit breaker if you go this route.

Eric

[paulr]

Thanks Paul,
Is the emergence time also relative to developer depletion?

i never tried to use it that way ... always just discarded the developer when it showed signs of weakening.

my inclination is to think it would work, but with limitations. one of ways developer gets exhausted is through the increasing concentration of bromide salts, which act as a restrainer. this process might effect emergence time differently than the developing agents themselves depleting.

maybe someone else can say with more certainty.

[Keith Pitman]

I have a small oil-filled radiator in my darkroom that keeps the temperature comfortable. I try to keep my developer in the 68 - 70 degree F range. I keep a thermometer in the tray and periodically immerse a stainless beaker containing hot water in the developer.

[Gary L. Quay]

I use a space heater to warm my darkroom to 68 degrees. I leave it at that temperature for a couple of hours before using it. That allows all liquids to reach the disired temperature. It works well. I have a fairly efficient heater, so it's not too expensive. The good thing about doing this is I can do whatever process I like without having to heat chemicals. I use the Fotospeed Mono RA4 kit, so I can print in color at room temp, although, I just bought a Jobo, so that may change.

--Gary