"The Natural Philosopher" wrote in message
...
Ian_m wrote:


or finally etching surface with chromic acid (nasty stuff) to produce a
"crust" which can then be glued.

That is a useful trick.

What is chromic acid?

A quick digging around on google reveals a chromic/sulphuric acid mix is
used to etch plastic prior to plating with metals and other plastic coating.

I had a moment that I thought my chemistry memory had failed me............