Quote Originally Posted by Steve Roberts View Post
What I'm using is the old-fashioned, traditional Sodium thiosulphate. Whether it's anhydrous or not - you've got me there! It's the only type I've ever come across - transparent crystals, elongated with several sides and up to a quarter inch in length, about an eighth diameter. My guess is that it's not anhydrous.

I agree that the amount of hypo is a key factor - too much gives no true blacks and blown highlights, though rating the film at a higher ASA can give usable though low contrast results. When you say that you're using a fraction of the hypo I am perhaps I'm not explaining myself well. I'm dissolving 20g of hypo in 200cc H2O, then using 10cc of this solution per gramme hypo required. At 4g/litre, for my 35mm tank, which requires 300cc of solution to cover one film, I'm using 12cc or effectively 1.2g hypo. How much do you use?

Steve - you are explaining yourself well. I understood correctly.

You are using 4g/L hypo.

For Rodinal I'm using around 0.76g/L, for Dokumol I'm using around 2.88g/L

You are using standard Sodium Thiosulphate (as confirmed by Rudeofus) whilst I'm using the anhydrous (which I now realise is the stronger of the two). Anhydrous is meant to be 1.6 times stronger by weight - and that largely explains the difference.

I was interested that Rodinal seemed to require approx. 1/4 the hypo needed with Dokumol when I tried it.

The fact that you have got where you are after 10 films is admirable!