Etching sterling, fine silver and gold

Does anyone know the ratio of Nitric Acid:Water that will bite
silver with a fine looking line etch? (No jagged edges)

Will sterling silver contaminate a nitric acid bath since sterling
has so much copper in it?

Are there any other types of acid that I can use to etch with,
preferably less toxic?

What kinds of acid can you use on gold and with what karat?

Answers to any of the questions would be a great help. Thanks,

Further Readings
Ganoksin’s Library > Surface Manipulation > Etching

Etching - Ganoksin Jewelry Making Community

Kerri Parker
info@kerriparker.com