Polymetaal

Ferric chloride is being used as a mordant for copper and zinc a long time. There are advantages in comparison with etching with nitric acid:

• it etches more regularly than nitric acid
• "under etching" is less an issue than with nitric acid
• less aggressive with makes it more precise
• safer, no aggressive fumes
• it is a salt and not an acid.

Disadvantages:

• it etches slower than nitric acid
• the liquid is not transparent, you cannot see the etching process visually.

Some links to pages with more information about ferric chloride.

• "classing etching" with ferric chloride
• the "Edinburgh-etch" to enhance the etching speed by using additives
• safetysheet of ferric chloride