The Darkroom Cookbook Forum

I don't have my DRC with me. What is the rule of thumb re weights when using this stuff in place of darkroom grade sodium carbonate?

Bake a measured amount for about 2 hours at 200°F/93°C to see if you need to adjust. My box started as anhydrous (baked equaled start) and it gained weight when I found it moved to the laundry room. Always test when the chain of custody is broken .



Dryer is vented indoors during the winter. I've paid for the heat and moisture - no need to waste it on the neighbor's car.





EDIT:

Thought my temps were a bit off. 250°F/120 °C.

Weight loss <4% - hydrate

about 20% - monohydrate

50% - decahydrate

Is the correct amount something I could determine with litmus paper?

Litmus paper is not a very precise testing method - it will provide you with a ball park figure. What I would like to ask is why you wish to use supermarket grade carbonate? The important difference between supermarket and photo quality is the purity of the carbonate. S/m quality is loaded with impurities that are not measured and can vary from box to box - even the impurities can be different.



If you are using carbonate in your film developer you are being penny wise and pound foolish to take a chance with your negatives using s/m grade. If you are using it in your print developer you will have inconsistent results. The only reason to use s/m grade is if nothing else is available to you (you don't live in the Borneo jungle, do you?).



Sodium carbonate from the Formulary is not that expensive. If you use a lot buy a bulk container.

sanchell wrote: Litmus paper is not a very precise testing method - it will provide you with a ball park figure. What I would like to ask is why you wish to use supermarket grade carbonate? The important difference between supermarket and photo quality is the purity of the carbonate. S/m quality is loaded with impurities that are not measured and can vary from box to box - even the impurities can be different.



If you are using carbonate in your film developer you are being penny wise and pound foolish to take a chance with your negatives using s/m grade. If you are using it in your print developer you will have inconsistent results. The only reason to use s/m grade is if nothing else is available to you (you don't live in the Borneo jungle, do you?).



Sodium carbonate from the Formulary is not that expensive. If you use a lot buy a bulk container.




ABSOLUTELY!!! Personally we use only the purest chemicals we can find, especially for film. When it comes to your film, you only get one chance. It is not a place to cut corners. We mix all stock solutions in distilled water.



There you have my 2cents worth from years of making mistakes. . .



FYI, another very good source of photo chemicals is ArtCraft Chemicals, Inc. . .

http://www.artcraftchemicals.com

Supermarket washing soda is fine for home brew wash aids and the caffenol crowd loves it for developer compounding. I get better results with the swimming pool pH Plus for the same uses. For my day job, I use chemicals from Artcraft with the occasional nod to Photographer's Formulary.

I guess I'm being hard headed & cheap. Better safe than sorry. Just placed my PF order.