Description of Pate de Verre and How it’s Created:
Pate de verre, the technique of pressing glass powders or frits into a mould, is a detailed and difficult form of kiln casting. However, it is the use of these fine frits that give pate de verre its distinctive luster and allows for specific placement of colours in the mould. Pate de verre utilizes the ‘lost wax’ casting method that other art objects are made of, from bronze sculpture to gold and silver jewellery.
Each piece starts with a wax model. The model can be an original carving or a duplicate made from a reproduction mould that is poured around the original carving. A model is an exact replica of the finished piece and every model starts with an idea. Once you have a picture in your mind of what you want to create, you gather the design elements. The next step is to make moulds and patterns from the various elements and then, wax reproductions. Once all the pieces are ready, you arrange and re-arrange until you have a composition that you are satisfied with. After the rough composition is done, you permanently attach the elements to the vase and then start filling in all the open and void spaces. When all the holes are filled and everything is attached, that’s when you can start to refine, sculpt, and clean up the shapes and forms. Last of all, the small detail is added for example leaves or flowers or in the case of our plate the butterfly. Before the mould can be made, the entire model is smoothed. When the model is ready, it is glued down onto the mould jig and a sheet metal dam is wrapped around it. Then the mould formula is mixed and the investment material is poured over the model. When the investment is set, the dam is removed. The was model is then steamed out of the mould, hence the term ‘lost wax’. At this point the model is gone forever and the outside mould is ready. The second piece of the mould, the core, is poured in a similar fashion using the core jig. After the mould is completed it is inspected and cleaned up. Some small details are carved directly into the mould. The volume of glass required to fill the mould is calculated and the colours are selected and weighed out into appropriate amounts. Frit is mixed with gum arabic to form a sort of paste and the colours are placed selectively into the mould with small spoons, scoops, and spatulas.
After all the glass has been placed in the mould, the core is set on top and it is set in the kiln and slowly brought up to casting temperature (1400 ~ 1550 degrees) where it ‘cooks’ until the glass has cast. When the casting has finished, it is reduced to the annealing temperature where it must rest awhile. Finally the kiln is slowly cooled over a period of many hours or days. If the kiln is cooled down to rapidly, the piece will crack. When it is completely cool, it is removed from the kiln and the mould is broken away. Once all the mould material is removed, the piece is cleaned. The amount of cold work, including hand finished surface chasing and enamel colouring, that each piece requires varies with the quality and importance of the item and this contributes significantly to its value.