Sunday, October 31, 2010

The Joy of Metal Clay - Bronze Patina, an experiment in ammonia fuming

It is Halloween so let's mix up a potion for our metal clay!
Last week, I talked about firing FastFire BronzClay. This week I am going to take the bracelet from that experiment and discuss using a technique called ammonia fuming to patina it.

About a year ago I was inspired by a piece and directions I found from the Squidoo Lens on BronzClay by Margaret Schindel. It is an extensive discussion about the original BronzClay (which is different than the FastFire BronzClay that I was discussing over that last two weeks). This site contains lots of useful ideas and tips (Squidoo Lens on BronzClay). If you scroll through the copious information you will find a section on finishing your bronze and more specifically there is a beautiful photograph of a turquoise coloured piece by Celie Fago and a short description on using ammonia to fume your bronze clay pieces. It was from this that I got inspired.

Here is the piece I made last summer:

BEFORE I start, remember to consider safety. Ammonia is an harsh chemical; read the label and take precautions. Consider using a respirator as the fumes are HARSH and dangerous. The label on my ammonia container states: "MAY IRRITATE EYES AND SKIN. DO NOT MIX WITH BLEACH. DO NOT GET IN EYES OR ON SKIN OR CLOTHING. DO NOT BREATHE IN FUMES..."

Here is what I did:

First I poured household ammonia (found at the grocery store) into a glass jar.

Then I took some wire and shaped it so that I could suspend the pieces in the jar so that they were not touching the ammonia and I hung the wire over the edges of the jar. I then covered the jar with a plastic wrap and left the container to sit. The article recommends allowing it to sit for 24 hours to 10 days).

Here is a photograph after 12 hours.

Here are the pieces after 36 hours.

And here is the original as a reference:

The pieces haven't achieved the colour I was hoping for so I have put them back in the jar for this week and will add a picture next week. Notice that the colour is not even, I am not sure whether this will correct over time, I guess we will have to wait and see.

Happy Halloween!

Remember to keep safety in mind when you are mixing up your potions.

1 comment:

Metals said...

If it is already painted, you have a few choices. You can try to strip the existing paint off, or you can use an oil based primer. Trying to get a bronze patina is not easy, but it can be done with a little practice.
Once you have your work piece primed, start with a coat of gold paint. Let this coat dry completely before continuing.
Next get some Olive Drab Green and put a light coat of this on top of the gold. Before this coat dries, take some paint thinner on a sponge and lightly dab the green pant in some areas. Remember, a natural patina is not at all uniform so the best way to determine where and how much paint to remove it would be a good thing to get a photograph of a bronze sculpture and just look at that finish. There are some examples on the website of
Once this step is complete, mix a very small amount of gray paint into the green. Again look at your photo or whatever you have as a template, and little by little add and mix until you think it is light enough. Make sure to reserve a small amount of this because you will need it later. Get another sponge and use this to apply this paint. Do not use the one you had the thinner on, but keep it close by.
Dab this lighter green color around and remember not to be consistent. When this dries, take the sponge you used with the thinner. Get the green paint you reserved and mix a little more gray paint along with a generous amount of paint thinner into this until you get the consistency of ink. Stand your gate up against something and soak the sponge in this paint and squeeze a small amount of this paint onto it and let it run down.
I know this sounds like a lot to have to go through, but keep in mind that you are doing in days what it takes nature months or years to do. My advice would be to try this technique on something other than your gate as practice. One more hint would be to make the effect more pronounced as you go toward the bottom of the gate, because this is exactly how it works naturally. Don't get discouraged if you don't get it just right the first time.
Good luck and I hope this