Giovanni, you are right, silvering was a thing of the past. As early as 1961 J.B. Sidgwick wrote that vacuum coated aluminium had taken over, noting also that the silvering chemicals were difficult to obtain by members of the public. I remember trying to obtain potassium nitrate for a different purpose and thought they were going to call the cops. Now almost anything is available mail order. I suggest the cost/benefit is perhaps shifting back to silvering. It is not just the cost of aluminising. There is no way I am trusting my mirror set to a courier, when a master optician said in 2016 that to make it then would cost between £6k-£10k. So I’d have drive it there myself and collect it afterwards.
If you can, read Jerry Oltion’s short article, pages 74 & 75 in Sky & Telescope January 2020,
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