At last it's here. I've been toying with the idea of switching to non-toxic etching for about a decade. The building of a new studio is the chance to turn over a new leaf so I've built the facilities with this in mind from the start.
It's only a partial switch, oil based grounds remain but nitric acid has gone in favour of Edinburgh Etch. I've tested it this week and it's marvellous, and, dare I say it, better than nitric.
Edinburgh Etch is a mixture of Ferric Chloride and Citric Acid. Ferric Chloride has been used for more than a century but it has the drawback if leaving a filthy rust residue in the etched lines, but Citric Acid removes that. It feels miraculous.