Both Ilford and Agfa gave details for making your own HCA.
Agfa recommend using Carbonate in their literature for fibre based paper processing, the Ilford bit is in Mason's Photographic Processing Chemistry, (he was head chemist a few years ago) where he recommends using Sodium Sulphite.
The chemicals have no effect on the image at all, they help to make the residual traces of silver complexes formed during fixing more soluble, and so easier to remove.
Most of the research was carried out during WW2 when it was discovered that salt (sea) water used to wash prints on board navy ships accelerated the washing process.
The chemicals used in HCA / wash aids are very soluble in water so wash out extremely quickly.
Originally Posted by RalphLambrecht