What's an example of washing soda I can get from a chain store? I have no idea. Ratio to water would help also.
I haven't mentioned that I also plonked in a pair of lower Victa handle stems (the ones that mount to the sides of the alloy hi arch frame) which are stress bearing. Hope they don't crumble in use!

Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!