Firing at High Altitudes – and a Project for White Bronze, Copper, and Bronze Clay

Following the question I asked in my last posting, about firing at high altitudes, here is what I understand. The warming pans and the kilns were not overheating. The temperatures were correct. However, at higher altitudes, for plastic to melt, for water to boil, and for metal clay to sinter, lower temperatures are required.

Because of lower air pressure, the liquids in the clay evaporate faster than at sea level, and the gases trapped in it expand and escape faster.

So the higher the altitude is above sea level, the lower the sintering temperature will be, and the lower the altitude, the higher the sintering temperature.

Thanks to Gail, Kim, Peggy and Mary for their input.

Here is a project combining copper, bronze, and White Bronze clay. This project is hard to do with silver clay because of the reaction between silver and bronze.

t-3-tone rock

This is a hollow form, constructed using the instructions for making a rock (see my first book, p. 69).

1. Choose a rock and cover it with a 2-card layer of bronze clay. Dry.


2. Cut the bronze layer in half and pull out the rock. Put the two halves back together and dry.

3. Cover the bronze hollow form with a layer of copper clay, 3 cards thick. Don’t dry yet.


4. Using a tube, cut a hole in the copper layer. Use a knife to cut a strip off the copper layer, continuing all around the rock. Now dry the rock.


5. Fill the round hole with bronze clay. Just “smoosh” it tight into the hole to make sure it touches the base bronze layer. It’s not important if you fill too much. Dry.


6. Use a sponge sanding pad to sand off the excess bronze, until the shape of the hole re-appears.


7. Position the rock the way you want it to hang. Drill a hole through the top third of it.


8. Fill the rock almost full with carbon. Fire it according to the instructions for your clay.


9. Clean the strip part using a radial disc or any other buffing/brushing tool. Fill it with White Bronze the same way you filled the hole. Dry.


10. Sand the excess White Bronze until the shape of the strip re-appears.

11. Fire the rock following the firing schedule for White Bronze.

12. Sand the whole rock smooth and flush.


13. Paint the rock with Baldwin’s patina to highlight the contrast between the metals. It will react with the copper, but not with the bronze and White Bronze. Wash the rock in warm water.


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