Chemistry question?

[Shen45]

Can anyone comment on the difference caused in a developer formula where the Hydroquinone is increased half a gram in a one litre formula.

Original

2.2 Metol
50 SS
5.5 Hydroquinone
2.5 Borax
2 Potassium Carbonate

pH approx 8.9


Curious if anyone has a chemistry background

2.2 Metol
50 SS
6 Hydroquinone *********
2.5 Borax
2 Potassium Carbonate

Steve

[BradS]

I'm not a chemistry person but have mixed my own for a while now and I'm gonna guess that the difference in this case is pretty insignificant. Half a gram in six is less than a ten percent error. At one time that might have been considered within measurement error.

[Darren Kruger]

Can anyone comment on the difference caused in a developer formula where the Hydroquinone is increased half a gram in a one litre formula.

Hydroquinone is one of the reducing (developing) agents in the formula, along with Metol. I think the HQ provides the deeper blacks, so by the .5 gram increase I think you would get a more contrasty developer. I do not know if you will be able to notice the difference though.

-Darren

[Shen45]

Thanks for the answers guys. The biggest difference I have noticed in the developers I have "designed" :) , is the pH and any changes introduced with different alkali has a dramatic impact.

Steve

[Richard Wall]

An increase in Hydroquinone is likely to give a boost to contrast, as it helps to build density. However, at such a low increase you are not likely to see much of a difference between the two recipes. (But I could be wrong, I typically use it with paper development, and a lot goes a little way)

There is a great book called "The Darkroom Cookbook" by Stephen G. Anchell that is a great book for tweaking developing recipes. I think it is out of print, but if you can find it, it is a wealth of information.

Richard

[Ole Tjugen]

I don't think an increase of less than 10% is going to make any difference.

Your pH is rather low, and increasing that would be the easiest way to increase the activity of the hydroquinone: Dropping the borax, and increasing the carbonate to 5g/liter should do the trick...

[IanG]

There is a great book called "The Darkroom Cookbook" by Stephen G. Anchell that is a great book for tweaking developing recipes. I think it is out of print, but if you can find it, it is a wealth of information.

Richard
The 3rd Edition of "The Darkroom Cookbook" is due out very soon, it's at the printers at the moment. I'm expecting a copy in the next 6-8 weeks.

The increase in the amount of Hydroquinone isn't likely to have any appreciable effects.

What's more important is what changes is Steve actually after. Ole's suggestion of "Dropping the borax, and increasing the carbonate to 5g/liter..." is likely to change the developer quite significantly by increasing the grain & contrast.

Ian