I have been trying to get some washing soda aka sodium carbonate to use as bleach for cyanotypes rather than using ammonia. All the brands I have seen locally seem to have other things in them such as surfactants. I don't know if these are bad or not. I have some potassium carbonate already and thinking back to my schoolboy chemistry days was thinking that this might act in a similar way to sodium carbonate. Anyone know?

Cheers,
Mark