Yanira's sculptures are made of clay, polyester resin and bronze. They are the result of individual processes of modeling, casting, finishing and patination that give to each piece Yanira's distinctive touch.

Clay

Yanira uses clay for modeling because it is soft and yielding in nature. Clay is easily shaped, enabling corrections as the final work is brought forward. It is often used as a transitory material before the ultimate casting is made in bronze, polyester resin or another more resistant material (Rich, 4).

Yanira uses clay also as a final material. If clay is baked at very high temperatures inside especial ovens, it achieves hardness and becomes more durable, yet it is still more fragile than other materials. Clay is not expensive and can be easily purchased. However, clay sculptures are unique, not cast, which adds additional value to them.

Natural modeling clays or terra cottas are found abundantly below the surface of the earth, but they need to be cleansed and refined before they can be used as a fine arts medium. Clay varies in color from blue to green, and it looks like a uniform body. For sculptural purposes, the lighter-colored clays are preferable because delicate modeling is more apparent (Rich, 23).

Polyester resin

It is probably the most widely used synthetic resin in sculpture, and the second most expensive material Yanira uses. Polyester resin is a plastic, which is durable, resistant to corrosion and relatively easy to handle (Mills, 188). It is mixed with an accelerator and a catalyst and poured into a plaster mold with silicone, which is made out of a transitory clay sculpture.

Here, the process of polymerization takes place as the casting is being made. The resin changes from a syrupy liquid to a jelly-like solid and then becomes cured and hard. The accelerator controls the curing speed and adds to hasten the chemical change from liquid to solid. The catalyst causes the resin to change into a hard and insoluble material (Mills, 147).

Polyester resin produces transparent or opaque solids and can be colored easily. If metal fillers such as alumina, metal powders or asbestos are added to the mix, the results are a wide range of color effects (Mills, 149).

Yanira's artistic ethic limits her to make up to seven copies of each piece though plaster molds can be reused several times more. The resin sculptures are individually polished using especial sandpapers and equipment. Then, they undergo a patination process that result in a change of color and texture of the surface, giving an aging effect usually green (Mills, 165).

Bronze

Bronze is the most widely used metal in sculpturing, and it is also the most expensive and heaviest material Yanira uses. It has a high structural strength, great physical permanence and resistance to atmospheric corrosion. Bronze also provides a fine, compact surface that allows for excellent finishing and patina (Rich, 135).

Yanira's bronze sculptures are cast in wax molds where the fused bronze is poured. Wax is fragile and easily removable once the metal has cooled. It has the adequate porosity for the heat to escape, and its fine texture allows registering delicate details and modeling. Wax molds yield a single bronze casting because they are destroyed in the process (Rich, 146). Bronze casts are done in ovens placed below the earth's surface or in especial fusing locations due to the extreme temperatures and especial techniques required to polish the surface.

Bronze is basically an alloy of copper and tin, yet other metals are occasionally added for color proposes. Its can range from pure silvery to a golden-yellow color (Rich 135). Yanira's bronze sculptures also undergo a patination process in which the surface is treated with acids and heat. Such acids provide cleaning agents to etch the surface or change the color (Mills, 8). Bronze patination must be done with much care due to the dangerous chemicals used.

Bibliography

Mills, John. Encyclopedia for Sculpture Techniques First edition. 1990

Rich, Jack. The Material and Methods of Sculpture. New York. Dover Publications, Inc. 1998

Interviews with Yanira Rodríguez Sosa. November 2005