Hi Kal,
generally wash aid mixed solution is used as a one session only item. You may be able to use it again but how do you check if it is still working or not?
It is usually one of the cheaper items that darkroom users buy, especially if you buy one of two basic chemicals and mix your own each time.
You can use about a tablespoon per litre of water, I believe, of either sodium sulfite or sodium carbonate (washing soda). I have prints from the early 1970's, when I first started printing, where the prints were given a quick wash after fixing and then put in a washing soda solution, before another wash. None of them have shown any mark or deterioration since.
Here is a quote from just one of the many pages explaining the process;
'You can buy wash aids, or make your own. To make a wash aid, make up a 2% solution of sodium sulfite in water (20 grams of sulfite in a litre of solution).
After removing the film from the fixer, rinse it thoroughly in water to remove fixer from the surface, then immerse it for about a minute in the sulfite solution, agitating continuously. Sulfite ions in the solution will react with thiosulfate ions in the emulsion, forming a complex that is easily washed from the gelatin.
Then a five-minute wash in running water, or five or six consecutive changes of water (with agitation, at least one minute per change) removes virtually all of the thiosulfate-sulfite complex.'
Terry S
