Critique Welcomed Och,...no Another Bliddy Fotie!

[Brian Moore]

Feel free to include it in your blog post!

I will. I've got a rough draft. I'll give you credit.

 

[Paul Lange]

To go from anhydrous to the decahydrate (i.e. 10 H20) you need to use the following calculation: 285.99 x (weight required / 105.99). The different forms have different crystal structures and so have more of less water associated with them. Once dissolved they are identical but you need to take account of the amount of water in the crystals. The molecular weight of anhydrous Na2CO3 105.99 and so to calculate how much of any hydrated form is required you need you adjust the weight required by the ratio of the weight of the hydrated form to the anhydrous form. Above is for the decahydrate, i.e. 105.99 + (10 x 18 [molecular weight of water]); so for the monohydrate it would be 105.99 + 18 and for the heptahydrate 105.99 + (7 x 18).

I apologise on behalf of Pete, he's a scientist and can't help it.

You need to use 2.7 times the amount of Decahydrate than anhydrous.

The recipe I use for slow films - ISO 50 to 125 is:

per 1/2 litre of water

73 gm Decahydrate soda crystals (from all good and crap supermarkets)
8 gm Vit C powder
20 gm Instant Coffee

 

[Paul Lange]

Oh I forgot to mention that you are supposed to push the film 1 or 2 stops but I have never done this and had no issues.

15 minutes at 20 deg C with 10 agitation at the start and then 3 every minute.

 

[Brian Moore]

Oh I forgot to mention that you are supposed to push the film 1 or 2 stops but I have never done this and had no issues.

15 minutes at 20 deg C with 10 agitation at the start and then 3 every minute.

@Paul Lange I am preparing a blog post on Caffenol for RPF. Do you mind if I include your recipe above and credit you? Note: I also plan (and have permission) to include the scientific treatise offered above by Professor Cuthbert Calculus. (@Pete Askew: ).

 

[Paul Lange]

Yeah, no problem at all but you should also credit the Caffenol Cookbook as my recipe is really just Caffenol C-M but with decahydrate soda crystals factored in and transposed for 1/2 litre. I have just ordered some potassium bromide and when I get round to it will make up some Caffenol for fast films developed using a stand process. I will let you know the result if you like?

 

[Brian Moore]

Yeah, no problem at all but you should also credit the Caffenol Cookbook as my recipe is really just Caffenol C-M but with decahydrate soda crystals factored in and transposed for 1/2 litre. I have just ordered some potassium bromide and when I get round to it will make up some Caffenol for fast films developed using a stand process. I will let you know the result if you like?

Yes Paul, the Cookbook gets its time in the sun in my little blog post. And yes, I'd be glad to hear the results of your caffenol stand dev. Thanks, Paul,