Back to Ganoksin | FAQ | Contact

Edinburgh Etch with ferric chloride

In the article by Gail Nelson on the Edinburgh Etch:

“Better - Safer Etching Metal Salt Etching, Resists and Resist

the recipe calls for a 4/5 saturated solution of ferric chloride
(40%) plus a 1/5 citric acid solution (3/4 hot tap water to 1/4
anhydrous citric acid). Then it gives an example:

16 oz. ferric chloride
3 oz hot tap water
1 oz citric acid powder

I get how to put together the citric acid part, but Bryant Labs is
out of powdered ferric chloride right now, and all I have is the
premixed liquid ferric chloride from Radio Shack. Does anyone know
if it’s a 4/5 saturated solution – and what does the “40%” mean?
There’s no on the label. Can I just add the citric acid
and hot water directly to the liquid ferric chloride?

If I was going to mix the solution using powdered ferric chloride,
surely I would add even more water to the above example?