I did some searching, on here and am not finding much.

I am looking for the formula for determining the temperature compensation for developers. Based on what I remember from chemistry class, I came up with the following formula:

(10th root of 2)^ΔT for Celcius.

[10th root of 2 raised to the differece in temperature]

When looking at some of the charts I found online, it does not match up.

There is no rule AFAIK for adjusting development time with temperature. Kodak has published curves for time vs temp for several film and developer combinations. Some are posted on their web site.

I did some searching, on here and am not finding much.

I am looking for the formula for determining the temperature compensation for developers. Based on what I remember from chemistry class, I came up with the following formula:

(10th root of 2)^ΔT for Celcius.

[10th root of 2 raised to the differece in temperature]

When looking at some of the charts I found online, it does not match up.

Anyone out here know the formula?

Thanks,

Jason

Jason

Developers with one agent can have a defined delta, but each agent is different, although most of the common ones are pretty similar. Developers with two agents, with the ususal hydroquinone as one, is valid only in a narrow range. HQ changes activity at four times the rate of Metol, for instance (IIRC). Therefore, the negative characteristics will change with any significant change in temperature.

I posted a .pdf chart there for D-76 time vs temp data from Kodak for multiple films. I've seen some formulae posted by Michael Covington and by others here on APUG, and also ran a regression recently to find out what made the Kodak Darkroom Dataguide development time vs temp wheel work. I got formulae, but if you look at the various specific manufacturer's time vs temp charts, you'll find that the formulae and curves found lying around are mostly generic, and designed to be close for most films and developers, and are probably close to exactly correct in a few cases.

P.E. and others have the answer, there's not a single answer/formula for all films or all developers.

I did some searching, on here and am not finding much.

I am looking for the formula for determining the temperature compensation for developers. Based on what I remember from chemistry class, I came up with the following formula:

(10th root of 2)^ΔT for Celcius.

[10th root of 2 raised to the differece in temperature]

When looking at some of the charts I found online, it does not match up.

Anyone out here know the formula?

Thanks,

Jason

Jason

Yes, Jason: The Arrhenius Rate Law is applicable
Rate = A exp(-B/T)

The constants A and B in the Arrhenius rate law are empirical and differ from one reaction to another. However, the empirical values of B are found to be similar for many chemical reactions. One result of this similarity is the useful generalization that for many reactions which occur near room temperature, a temperature increase of 10oC approximately doubles the rate of the reaction.

I use algebra to obtain the necessary constants from the published Kodak, Ilford, etc time and temperature development data for specific films and developers.

For years I used this equation with a 'room temp.' method. The equation is taken from the Kodak darkroom dataguide. I remember using my first computer (Commadore 65) to decode the Kodak wheel back in the 80s. Later I put the equation into an Excel spreadsheet.