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Greening Copper with Ammonium Chloride
Article © MAIL User: Drax

Ammonium Chloride -- Greening Patina

Target metals: Copper, Brass, Bronze
Target colors: Green

Application of this solution to copper containing metals will form a green patina on them, the same color as the Statue of Liberty (for the same reasons).

This recipe comes from The Complete Metalsmith, by Tim McCreight.

Be careful of the ammonia -- the fumes are particularly noxious.

To make this solution, mix together:

1Tb Ammonium Chloride (NH4Cl, also known as sal ammoniac)
1Tb Sodium Chloride (NaCl, table salt)
1oz Ammonia
1qt Water (H2O)

Mix all items together. The ammonium chloride may take some time to dissolve, warmer water will speed this up.

Method of use: You can dip the items to color into the solution, or you can use a spray bottle (recommended). It took over 10 applications for me to get decent accumulation of green on the metals. (1 application means spraying and then waiting a couple of minutes.)

The copper wire was completely covered in the green patina, as well as the bronze. However the brass darkened and only had about 60% coverage. The patina flakes off VERY easily, especially under the pressure of pliers. It looks like it would wear off, though not completely, on a high use item. The best use for this would probably be on an immobile piece, or it could still impart a great-looking effect to a piece.

The picture shows a bronze ring and a brass ring with their "greened" equivalents below. On the far right is a small piece of copper wire that was greened.

Image: dab_cb_green.jpg
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