Writings

October 25, 2004
THE LOST WAX PROCESS


The Lost Wax Process is an intricate process that involves many steps. It takes the clay and transforms it into a finished bronze. It almost seems like a miracle when I am working on the clay to imagine that one day it could become bronze. Bronze is very exciting for me and the feel of the bronze always gives me a thrill when I reflect on all that went into creating it.

I have broken the process into 17 steps, each different and each necessary.
1. the inspiration.
2. making the armature.
3. creating the clay sculpture.
4. making the rubber mold.
5. making the wax replica of the sculpture.
6. fixing up and cleaning the wax. (this process is called chasing)
7. applying the sprue system.
8. investing the wax.
9. burning the wax out of the investment.
10. pouring the metal into the mold.
11. breaking off the investment.
12.cleaning up the casting, and sand blasting it clean.
13. welding, chasing and finishing the bronze.
14. preparing the sculpture and the base for mounting.
15. applying the patina.
16. mounting the base.
17. exhibiting the sculpture.

Before we quickly go through these steps to see what is involved in each of the sculptures you see around you, I would like to guide you through a brief history of bronze casting.

BRIEF HISTORY

Bronze casting came into being when an astounding event happened. Somehow, some tin got mixed with molten copper, and when it hardened the mixture was harder than either tin or copper alone. The Bronze Age began with this discovery, somewhere between 3 to 4,000 BC.

About 7,000 years ago, however, evidence indicates that the lost wax process of casting metal was used in Egypt, prior to the discovery of bronze. Clay was layered over a wax sculpture and hardened by firing. Metal was then melted and poured into the cavity where the wax was. About 2,500 years ago, a major breakthrough occurred in Greece, when hollow casting was invented. This process enabled sculptors to make large figures because only a thin layer of bronze was needed for the casting.

Up until the Industrial Revolution, each bronze casting was a one of a kind sculpture. It was impossible to make multiple copies from the mold because the mold was broken when the sculpture was removed. With new technology, mold making was gradually improved so that a number of sculptures could be made from one original.

THE INSPIRATION

Perhaps the hardest part of the whole process is coming up with an inspiration of something to create, something that is worth spending my precious time on. On the one hand this can be simple if I choose to create anything that quickly comes to mind. On the other hand, to create a work that says what I really want to say is another matter. I can go for a long time without an "inspiration," when the muse may be hovering nearby or far off, but certainly is not lighting on my head. I often search for an idea in vain as nothing comes to me that excites me enough for which to build an armature, the first tangible step in the process.

The Idea is such an important part because it will express something real about the artist. "How does that symbolize your existence?" a teacher would ask me, reaching deeper than a discussion about line, form, mass, etc. In each piece I create, I can answer that question, difficult as it always is. It may take months of working and many attempts and failures as I realize that what I am working on is not really expressing who I am or what I want to say. When I work, I work towards finding a shape, a line or form that "symbolizes my existence" in some way and a sculpture is finished when I finally can say, "yes," this in part is who I am.

THE ARMATURE

Creating the armature is like creating the backbone of the sculpture. Too many of my sculptures have failed because well along in the modeling the clay got too heavy, for example, and the figure began to bend and sag in inconvenient places and in uncontrollable ways. Always learning the hard way, I learned that the key is to build a strong armature, one fully adequate for the job. On this strong foundation what I create will stand.

MODELING

I use plasticene because it works well, giving me the texture and detail I want and it doesn’t harden. Plasticene is clay in which the water has been replaced by oil. Therefore it can’t be fired. I love the feel of plasticene and its fragrance, and working it in my hands is exciting. I can’t really answer the question, why clay and not paint or yarn or food? Everyone is drawn to some way or ways of expressing creativity. As a boy in the Clay Pond, I found that I loved to work in clay and that love has only increased over time.

THE MOLD

There are many kinds of molds. The one I use most often is the rubber mold.
In itself, making a rubber mold is a complicated process, but well worth it because it enables me to make additional copies from a single sculpture. I apply a liquid rubber mixture over the platicene sculpture and wait for the rubber to harden. I apply plaster over the rubber in order to enable the rubber to hold its shape. Simple molds are made of two halves put together. The one on display used three pieces because the figure of the child needed its own system.
When a sculpture is more complex, the number of parts would increase and the separate wax pieces would later be put together.

CREATING A WAX CASTING

I split open the mold into two halves and remove the clay by carefully digging it out. I then put the mold back together, binding it so the seams are tight and able to receive the molten wax. Then I pour the wax into the mold, hoping that it won’t leak out and run all over the place.

There are many kinds of wax and I buy a wax that is used by sculptors. After the wax hardens, I carefully remove the wax by dividing the mold made of rubber and plaster, and gently removing the wax figure from the rubber. If the wax breaks, which it often does, it is not too difficult to heat up the broken edges and fasten them back together again.

I come to the next phase, which is called chasing. By chasing the wax I mean that I am cleaning, carving, removing, adding, and doing whatever needs to be done to the wax to make it conform as perfectly as I can to my idea of the finished sculpture.

CREATING A SPRUE SYSTEM

Because molten bronze will be poured into the investment—the hollow shell that surrounds the wax--- (I will get to this shortly) I have to prepare for hot gasses to bubble up and escape so that no bubbles and unwanted holes will exist in the final bronze. Each sculpture requires a unique sprue system made for itself. Sprues are make of wax and are melted away when the wax is "lost,"
forming hollow passage ways through which the bronze can pour in and the gas can escape out. In the example here, you can see the bronze sprues around the area of the child’s arms.

INVESTING THE WAX

I next invest the wax. I use the ceramic shell process. I dip the sprued up wax into a liquid ceramic mixture a number of times letting it dry after each dipping, until it builds up a thickness of about 1/4 of an inch. This is called the investment.

BURNING OUT THE WAX

I next burn the wax out of the investment. The investment containing the wax is placed in a kiln and the heat burns out all of the wax over a number of hours. This is the moment in the lost wax process in which the wax is lost. At the end of the burning, I have an investment that is hollow and ready for the bronze.

POURING THE METAL

To melt the bronze, I go to a foundry. There, I place the empty investment in a small sand support, and after dressing up appropriately, I, with a helper, remove the molten bronze in its crucible from the furnace. We bring the crucible to the investment and carefully pour in the metal. Then I let it cool.

DEVESTING

This process starts with hammering off the ceramic shell. Hammering will remove most of the shell. The rest comes off with a chisel. What doesn’t come off with a chisel comes off when I subject the sculpture to a sand blaster. The sand hitting the bronze under pressure gets into the nooks and crannies and removes all the remaining shell (hopefully). I need to remove all the shell because the shell won’t take a patina and will remain white on the bronze surface.

CHASING AND FINISHING THE BRONZE

The bronze comes out of the investment with bronze rods from the sprue system attached and seams and many other major and minor unwanted blemishes. Now I take a cold chisel or a grinder or a cutter of some kind and cut off some metal. This is a painstaking part of the process because bronze simply doesn’t work as easily as plasticene.

MOUNTING THE BASE

With the bronze sculpture the way I want it, I must drill holes in the base for a bolt used to secure the sculpture onto the base. I drill a hole in the bronze and use a tap wrench to make the threads for the bolt. Finding the base I want is in itself a hard job, involving the right kind of wood, or other substance, with the right shape and finish. The base becomes part of the entire sculpture, just as a frame is to a painting or photograph.

APPLYING THE PATINA

This is a complicated process about which many books have been written. Some time ago I took a 4 day course on the application of patinas and at the end of the 4 days our instructor said he had been working steadily on patinas for 6 years and was just getting the hang of it. To make this long and fascinating story short, on most of my recent sculptures I used as a base a chemical called liver of sulfur (sulfurated potash). I applied that to the cold bronze. If too concentrated a mixture is used, the bronze becomes very dark or even black.
For the next layer, I used ferric nitrate. Using a torch, I heat up the bronze so that when the ferric, dissolved in water, is applied, the solution sizzles on the surface. The ferric adds a reddish hue to the bronze, giving it a warmer feeling. This ferric over liver is a very common patina formula. Of course lots of other chemicals and formulas can be used to create colors, ranging from blues, greens to black and white After applying the patina, I put on a coat of wax to protect the patina and to make it sparkle.

EXHIBITING THE BRONZE AND IDLE CONVERSATION

Now the base is put on and the piece is ready to be shown to friends. It is finished. I stand back and look at it and feel a touch of excitement.

About this time a friend will come up to me and ask, thinking that I am something of a wizard, "How did you do that?" "Oh" I say, "Oh my, very difficult. It takes years to learn. All those steps. Maybe after 6-8 years you might just get the hang of applying the patina. Yes, very difficult." I look thoughtful, and nod my head. But after reading this, you know that it is not that difficult. No wizardry at all. Just inspiration. Just a visit from the muse. Just time and dedication. And the time flies by because it is such fun.