Monday, December 24, 2012
08 Joint Design Nº 47
Wax and water do not mix. This is the basic principle behind casting molten carving wax into plaster molds. The plaster mold must be saturated in water before pouring the molten carving wax into the mold. In this photo I have completely submerged the plaster mold in a pail of warm water. Bubbles of air will start to rise from the plaster mold. How do I know when the plaster mold is completely saturated with water? Air bubbles stop rising from the plaster mold. I usually turn the mold several times while it is soaking to make sure that air has not been trapped in the mold when I submerged it. Click on any image to enlarge it.
While the plaster mold is soaking in warm water, I put my wax pot on the hot plate and turn it on. I have a mark on the rotary dial where the carving wax will just melt, without getting too hot and smoking. If the carving wax (or any wax being melted) smokes, it is way too hot. I always have to add more wax than I will need for the actual carving wax ball because I must fill up the mold to the top of the spare when I pour it. The carving wax will thicken up along the walls of the mold, and twhen it gets thick enough, I will empty the excess wax back into the wax pot, leaving a hollow carving wax casting.
Somewhere in the garden, I lost my black masonry tub that I usually use to soak molds in. So I put the plaster bat that I use to pour carving wax into when I am done casting, into the shower stall and filled it with water to soak.
Here are the water saturated mold halves, removed from the pail of water. When the mold is saturated, water will no longer be absorbed by the plaster. The standing water in the mold must be removed before pouring molten wax into the mold.
I use toilet tissue paper to dab out the standing water that is in the mold.
I band the mold together with rubber bands to ready the mold for pouring.
I always stir the carving wax in the wax pot before I pour it into a ladle. This stirring mixes up the talc that is on the bottom of the wax pot. Pouring from a ladle allows me to have more control over the pour.
I do not have any pictures of actually pouring the mold because I am too busy to take photos. This photo shows the mold after it was poured with carving wax, topped off with carving wax, then the excess carving wax poured back into the wax pot. To make sure I could pour the excess carving wax back into the wax pot, I stuck a stick into the spare opening and made sure the hole was large enough. Then I picked up the plaster mold and took it over to the wax pot, and carefully tilted the mold until the carving wax poured back into the pot in an even stream, without any gulps for air. It takes practice. Casting carving wax is good practice for casting slip later on.
I put the casting back in the pail of water so it could fill with water and cool off a little faster.
I like to take off the rubber bands while the mold is in the water. Then I open the mold carefully while it is in the water. Here is my first 76mm carving wax casting, half embedded in the opened plaster mold.
The 76mm carving wax ball is shown with the plaster mold which has been removed from the pail of water.
I dab out the excess water from the mold, in order to get it ready for the next carving wax pour.
The mold is baned together with rubber bands.
I add more carving wax to the wax pot so I will have enough wax to fill the mold.
I use a pair of heavy leather gloves to handle my wax pot. The wax pot I am using does not have any handles, and it is very hot.
Once again I pour the molten carving wax into the ladle, then pour the mold with the ladle. Once the carving wax has been poured into the water saturated plaster mold, topped off, then the excess poured back into the wax pot, I empty the wax pot into the water saturated plaster bat. When the carving wax solidifies, but is still soft, I use the paring knife to score it so it will be easier to break up for use later on.
I make sure that the wax pot is turned off and unplugged.
The carving wax casting has been cooling off in water in the pail.
Here is the second 76mm carving wax casting, along with the water saturated plaster mold it was pulled from.
There is now a 40mm mold, a 66mm mold, and a 76mm mold in my ball mold library.
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