The Lost Wax Process Bronze objects have been created for over 6000 years. Craftsmen used it because it melted easily and hardened to a durable finish. Around 4000 years ago, artists in Mesopotamia began using the “lost wax” process to create larger, hollow castings. The “lost wax” process is still in use today. Creating a bronze sculpture requires many steps. The artist of today first creates a model, typically in oil base clay. Rubber is applied to the surface of the model and a plaster “mother mold” is added to the rubber. The mold is made in multiple pieces and is then removed from the original model. The rubber and plaster mold is reassembled and filled with molten wax. The still liquid wax is poured out of the mold, leaving a thin wax shell. The rubber and plaster mold is disassembled and the wax pattern is removed. The surface of the wax is a copy of the original model, but will have some defects that must be touched up. A “sprue” system is added to the wax pattern. This creates a path for the metal to flow through. From here, the wax pattern is dipped into liquid ceramic slurry and then coated in sand. This step is repeated 5 times to create ceramic shell around and inside of the wax. The wax/shell is put into a kiln, heated to 1750° until all the wax has been melted out and the ceramic shell is fired to a hard surface. While the ceramic mold is still hot, silicon bronze that has been heated to 2100° is poured into the hollow space. After the mold has cooled, the ceramic material is removed, the bronze sprues are cut off and the piece is ready for finishing. It is important to note that in the US, most foundries use Silicon bronze. Silicon bronze is composed of 95.8% copper, 3.3% silicon, and 0.9% manganese. Silicon bronze is known for its easy pouring ability, lack of surface defects and superior corrosion resistant properties, even when submerged in liquids and chemicals. Foundries in China and other Eastern countries use a much lower quality bronze consisting of between 60-70% copper, often from recycled radiators and pipes. For quality castings, silicon bronze is by far the best choice. Now the piece is ready for finishing. Multiple castings are usually needed to create one sculpture. These different sections of the original piece need to be welded together. The seams must be ground down and chased to recreate the original texture. Any pits or other defects in the surface must also be repaired and made to match the original surface. Finally, the bronze sculpture is heated and chemicals are sprayed on the surface to create the “patina”, a colored finish. Several layers of wax are applied while the sculpture is warm to create a sheen on the surface and provide protection from the elements. Here are two examples of finished bronze sculptures. Care of Your Bronze Sculpture Once our customers have purchased a bronze sculpture, many have questions about how to care for it. Although a well-crafted bronze sculpture is very durable, it still requires some simple maintenance. Indoor sculpture should be dusted once a month. If it has gotten very dirty, mix a small amount of Ivory dish soap with water and using a soft rag, cotton pads and/or cotton swabs to wipe the surface of the bronze very carefully. A soft toothbrush can be used in tight places. Rinse thoroughly with distilled bottled water to avoid water spots. Once the piece is completely dry (a hair dryer on low will speed up the process), you can apply a thin coat of wax with a soft cloth and then buff the wax to a sheen. This is usually all you need to do to maintain your sculpture. If you are not able to clean the surface with Ivory soap, then use Dawn dish soap. However, because Dawn is a degreaser, it can remove the original wax on the surface. When the piece is clean and dry you will need to add 3-4 coats of wax, buffing in between each coat. Warming the surface with a hair dryer on low will help the wax penetrate the surface. Wax acts as a barrier to air and humidity, protecting your original patina. Johnson’s Clear Paste Wax is the best choice for darker patinas. Trewax Clear Paste Wax is better for lighter patinas. Johnson’s will slightly darken the surface color. Do not use automotive waxes. Always test a small area to make sure you are not removing the original patina before starting the cleaning process. Clean outdoor sculpture with the same techniques. You can use a gentle spray from a hose to rinse carefully. Try to wax outdoor sculptures during the heat of the day and again use 3-4 thin coats of wax. This wax coating should last about 3 months. If you see that water is not beading up in the surface, it is time to clean and wax again. When a sculpture has not been maintained, you may see the bronze oxidizing and turning green. Some people like this aged look on their bronze, though if left untreated, it can eventually damage the sculpture. If you prefer the original look, be sure to keep up with your maintenance schedule. If your sculpture has developed pitting, stains and black streaks, you may need to have a professional clean and possibly repair your sculpture. Contact Carolina Bronze Sculpture for cleaning, repatination, and repair on sculptures from small to large. The work can be done in our shop or on site. If required, a regular maintenance schedule can be set up. Copyright 2015, Carolina Bronze Sculpture, Inc 6108 Maple Springs Road Seagrove, NC 27341 (336) 873-8291 www.carolinabronze.com .