What Is Lox Wax Method?
The lost wax method is a method of casting, which is generally used for casting products whose three-dimensional structure is quite complex and that common molds (mold combination method) are not capable of. This method has been used to cast bronzes in ancient times, and it is called investment casting in modern precision casting. The beauty of the lost wax method is that it could make extremely complex and delicate metal products. Let us introduce some specific steps about this casting method.
Step 1: Mold Making
From the initial clay sculpture model, it is extremely critical. First, the main shape of the pattern is made of clay, including its curvature, the size of the flared mouth, the width and the thickness, which must be grasped by the hands and experience of the masters. This step is the most important step in the lost wax method, laying down the details of the follow-up.
Step 2: Flip the Mold
The original mold made of the clay model is coated with a layer of silicone, because silicone is soft, and gauze is attached to the outside, and finally fixed with plaster. The silicone is peeled off from the original mold, and the formed cavity is filled with melted paraffin, so that an identical wax mold could be obtained.
Step 3: Trim
The paraffin model taken from the silicone model, the imperfections need to be finely trimmed. Since the process of turning the mold must be upside down on the platform, several paraffin models are required for the shapes with lids and ears, and they must be carefully glued and polished by hand during the modification. Fine finishing work sometimes takes the masters a day.
Step 4: Carving
The finished paraffin model could be used for carving after a few days. Compared with gypsum, beeswax has good plasticity and is easy to process. The wax model could be carved more finely. The hair of lions and animals could be combed and trimmed slowly with a carving knife. This step fixes some of the details that were lost during the overmolding process, making the details of the sculpture you expect more vivid and refined.
Step 5: Hanging Sand
The ancient process was to finely coat the outside of the wax mold with moist clay and then apply thick layers of clay in preparation for the next step to form the cavity for pouring the bronze melt. The modern method is to first soak the wax mold in water glass solution. Water glass is also called Paohua alkali, and its chemical name is sodium metasilicate. Hang 5-6 layers of refractory materials on the outside, and even larger objects need to hang as many as 8-9 layers. After taking out, sprinkle quartz sand, put it in ammonium chloride solution to harden, and repeat the operation until a shell with sufficient strength of 5-10 mm is formed.
Step 6: Melt the Wax and Cast Copper Water
The mold shell is immersed in 80-95 degree water to remove the wax film, and then calcined to remove the residual wax to obtain a cavity mold shell. After the beeswax melts into a liquid when heated, it flows out of the pre-reserved small hole, and what remains is a hardened clay shell. At this time, the mold has changed from a solid mold to a hollow mold, and then the copper water could be poured.
Fill the outer shell with sand to increase strength and stability, and start casting. A hot bronze solution is poured into this clay shell, filling the space formerly occupied by beeswax. In the past, Xuande furnaces were mostly made of brass and precious metals such as gold and silver. Today’s copper smelting and purification technology is much more advanced than in ancient times. To avoid pores and trachoma, the ratio of copper and other metals is extremely important.
Step 7: Cool
Leave the cast copper furnace together with the refractory for a while.
Step 8: Shelling and Welding
After the red copper solidifies and cools, smash the clay or the heavy refractory shell, and you could take out the exquisite copper casting that is exactly the same as the earliest beeswax model.
The copper sheets after shelling are welded together according to the design to form the desired bronze sculpture.
Step 9: Sand and Polish
After repeated grinding and polishing, the copper furnace would emit a soft and bright luster from the inside out. Fine polishing is accompanied by the sound of sandpaper. Experienced masters need to be careful and grasp the strength. If you are not careful, the fine carvings obtained after dozens of processes may be turned into copper powder.
In fact, there are more than 30 crafts of the lost wax method, each of which is extremely fine and complex. It is precisely because of this that many bronze sculptures with wonderful details appear in front of people.