The Wax FAQ—Sculpting in Wax
Brown sculpting wax is the basic all-purpose type favored by many sculptors. It is a “microcrystaline” wax, which means it will bend a lot more readily than paraffin, the white wax used for making candles. Unlike paraffin, it also burns out without leaving an ash residue. Called “Victory Brown”, the type we get here is suitable for hand-modeling if you get it slightly warm, or for casting into molds. If you need a more malleable wax, there is also a “Victory Amber” which is similar but softer. If you are working in an unheated studio in the winter, it might be preferable, but complicated pieces can collapse in the summer if it gets too hot. For even greater malleability, you might try the type of soft wax used to coat cheese. There are harder waxes, such as Sierra Red, which are suitable for casting into molds, and will retain their shape better than the softer ones. Another is a pink wax sold in stick form for use as sprues. These can also be alloyed with the softer waxes to produce wax of an intermediate hardness.
There are also waxes formulated for carving rather than casting or modeling with the fingers. These often have a little polyethylene added to make them less sticky; but they won’t bend, and are difficult to weld. “Machineable” waxes are similar, but are more forgiving of welds, and permit remelting.
To use it directly, it’s best to make yourself a slab mold, either with rubber or plaster. This can be a simple one-piece mold of any flat smooth object, such as a plastic cutting board. Soak any plaster molds thoroughly in water before pouring melted wax into them; this will keep the wax from soaking in and sticking. Thinner sheets of wax may be obtained by tilting the mold; thicker ones by filling the mold and letting it set..You can break up the ten-pound block of wax by hitting it sharply with a hammer (if it isn’t too warm out). Make sure you’re doing this in a clean place; you don’t want to get debris in your wax if you can help it.
Melt the wax chunks in an electric frying kettle, making sure you keep the temperature under about 225 degrees Farenheit (it will melt considerably lower). It is best to get a fryer with an infinite range control, instead of low, medium, and high settings; and check it with a candy/frying thermometer to make sure it doesn’t get too hot. The wax can be dipped out of the fryer kettle with smaller pouring containers—I make my own by adding handles to steel cans. Never melt wax directly over an open flame—if that’s all you’ve got, use a double boiler. If it starts smoking this is not only bad for you, but the next thing you know you have a tower of flame where your wax used to be (and even if you don’t burn down your place, the carbon ruins the wax.). This is a messy process, so think twice before doing this in your kitchen. Spilled wax can make a big mess very quickly, and it is very difficult to clean up wax completely when it has spilled. Wear protective gear when pouring the wax, especially some rubber gloves and a face shield—this stuff can give you some nasty burns, just like deep fat frying. I like to put some beeswax into the mix; about 25% by volume. This makes it somewhat more malleable and gives it a nice smell. While sculptors have used beeswax its pure form for millennea, it works better as a component in an alloy.
Once you have cast sheets of wax 1/8-1/4 inch thick, you can use it more or less like clay, warming it in your hands or using a hair-dryer to warm larger pieces. Once it cools, it can be worked with tools, or you can use an electrically heated tool similar to a soldering iron (but not as hot) to weld it to itself. If you don’t have one of these, use an alcohol lamp to heat a steel tool, which will melt a little wax before it cools and must be reheated. Loop tools and steel “ribs” such as are used for sculpting clay may be used, as may all sorts of improvised tools. You can also buy sets of toothed scrapers which are designed for smoothing out the contours of plaster models. These leave a series of fine raised lines on the surface which graphically show any depressions that otherwise might escape the eye. These lines may be removed and the surface further smoothed by rubbing with a Scotchbrite abrasive non-woven pad dampened with some mineral spirits or kerosene. For a finer finish, use a nylon stocking .
If you keep the thickness under 3/8 inch or so and keep it even throughout, your model can be cast in bronze using the lost-wax method. However, it is usually better to make a mold and cast a new wax for lost-wax casting. This will ensure an even thickness in the casting, and is insurance against disaster, as well as affording the possibility of producing an edition rather than just one unique piece. Lost wax casting does require that a wax pattern must be sacrificed for each bronze piece that results; but it can either be your original or a copy that is lost.
If you are using wax to make a model which will be molded, you can use a wire armature, or a substructure made of any firm material, since the wax will stick to almost anything when it’s hot, and will not shrink. Like an oil painting, it is reworkable for an extended period, and may be added to or subtracted from at any time. You can also incorporate parts made of different materials and found objects, or weld together a series of wax castings, using a heated tool. (Much of my own sculpture is mastered this way). Once a wax cast is made from your model, it can still be embellished with combustible materials such as balsa wood, cloth, and styrene plastic; these will usually burn out cleanly and be reproduced faithfully in the bronze.
Thanks to Frank Egan and Dan Spector for their helpful suggestions on this FAQ.