Silver coloured bronze (or white bronze) is particularly difficult to fire, or my kiln has problems and the temperature is not even. Besides, this bronze does not have a very wide firing temperature range
When it overheats , the bronze starts to melt and the result is mostly a ball of metal . But every now and then some of the metal starts to bead up which gives a very interesting look. These near misses become really unique pieces that I keep and sell of course.
I have tried in vain to reproduce the phenomenon but it depends on the space in the kiln, the number of pieces firing, the location high up in the charcoal containers and I have had dozens of pieces lost for 1 or 2 such pieces.Besides, impossible to get this effect with yellow bronze or copper. 😀
A client wanted a voluminous plant style ring with pearls. I created this ring with the intention of putting 1 to 3 freshwater pearls in it. I had several types of freshwater pearls in different sizes and colours.
This technique of metallurgy by sintering. has been used since the 19th century (perhaps earlier but I have not found anything about it) to make titanium wire. The yellow bronze, bronze gold color, is made of 90% copper and 10% tin, the white bronze, silver color, is made of 80% copper and 20% tin. It all starts with metal dust ……. to 90 parts of this bronze or copper powder we add 10 parts of a cellulose binder (in the 19th century maizena. I add distilled water and I obtain a malleable paste resembling pottery clay and which can be worked in the same way. I can then model it, stamp it, mold it…
Then I let it dry gently, 1 to 2 days to avoid cracking , the pieces become very hard. I can then sculpt them, engrave them, sand them, chisel them, pre-polish them,
Then a first firing takes place at 350°C in an oxidizing atmosphere, that is, in the presence of oxygen (from the air) in order to burn the binder that would prevent sintering. The parts then become anthracite gray and are very fragile
The metal pieces are placed in containers , buried in charcoal. This creates an atmosphere known as “reducing” and the metal is fired away from oxygen , at 830°C for yellow bronze, 740°C for white bronze and 930°C for copper
When the parts come out of the furnace, the metal grains have welded together. The parts have shrunk by 10 to 20% and are oxidized, they must then be sanded, polished . Then I encaustic with a wax that I make myself composed of essence of orange peel and beeswax diluted with medical kerosene oil .I just have to mount them in bracelets, necklaces, earrings …