Patina

[HelleRaskCrawford]

Hi Olivier
The casting is done (have made about 20 pieces, most of them went very well ), now I am trying my hand at the patina.
Put a couple in hot NaOH. Let the dry and then left them in CH3COOH vapour for a couple of days and got a great green patina, but white effusions and brown discolourations keep showing up even when I don't wax the pieces. Any advice?
Thanks
Helle

[olivier]

Helle,

I must admit that I have never used Sodium hydroxide or Acetic acid for my patina... I am afraid I cannot give you any advice on that one..

For a green "verdigris" patina I used Cupric Nitrate... This is a great patina for outdoor display.
I can be very light in color if apllied very hot. I often darken it with a diluted liver ("liver of sulphur" or potassium sulphide) With experience it can also be used to make very deep black.

What I like about cupric is that you can make it sizzle on the hot metal creating light green rings. By making intersecting rings, you can very convincingly immitate marble veins...specially if applied over a dark liver...

Back to your problem... Anything acidic will continue to react and "seep" for a very long time and can even bring white marks to the surface after several months. Never a good a thing to have an unhappy customer calling you on the telephone with a complaint... as a rule I keep well clear of anything acidic... But your problem could be due to something else...

I have seen a friend making green, almost blue patina with vinegar vapors containing CH3COOH. it was beautiful but very fragile...

Sorry I cannot be of much help on that one...