Richard, thank you for the encouragement etc. I did attempt silvering 4 and 6-inch test pieces back in 2016 following the method of E. E. Hall in the 1965 June Journal. Results were patchy. Revisiting my 2016 notes today I seem to have missed out the cleaning/degreasing – oops! I do have 60% nitric acid in the cupboard so can use that as you suggest although it is horrid stuff. I will try using calcium carbonate first, as per the Youtube videos.
I had assumed the sprayers being used were ‘proper’ big-ticket paint sprayer kit but I now realise they are no more than the cheap greenhouse/garden things sold by garden centres.
I am also intrigued by the idea of perspex chips dissolved in a solvent as a guard coating. I have read that alum paper can slow down the tarnishing and will try that first.