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The Lost Wax Costing Method Process

The first step in creating a bronze sculpture using the lost wax casting method is to sculpt the original piece from which the mold will be made. All the detail is captured in this stage, which is the basis for the rest of the process.

The next step of casting is to pour molten wax into the mold, using layers of wax to form an exact duplicate of the original casting.

The wax is pulled from the mold and detailed, or chased, welded and polished by individual artisans. Each piece may contain some small variation from the original, but the reproductions remain true to the original sculpture.

Wax rods and pouring cups are attached to the wax casting to assure a full pour. Using a temperature controlled climate, the wax casting is dipped into investment liquid (liquid clay, essentially). After the first dip, a powder is applied to the clay, and on subsequent dips a layer of ceramic sand is applied, creating a ceramic mold that must be allowed to dry between layers.

The ceramic shell is then placed into a kiln and fired, the shell is baked and the wax is melted (lost) from the shell, creating a hollow ceramic shell mold and the phrase 'lost wax casting.' The mold is removed from the kiln, and molten bronze is poured into the shell at about 2100 degrees Fahrenheit.

After several hours of cooling, the unfinished bronze is carefully stripped of the ceramic shell. The ceramic shell fragments are carefully removed from the bronze, which is carefully inspected at this stage.

If required, this is the time when a master craftsman would weld larger sections together, and chase or re-detail the weld marks. Afterward, the craftsman uses a process called 'glass beading' in which the bronze is sprayed with powdered glass under extremely high pressures to ensure an even bronze finish.

The bronze is now hand polished and heated to await the patina application. The patina is hand applied by the artisan, and a layer of wax is hand applied with heat to ensure a lustrous patina finish. After a final inspection, the bronze sculpture is now ready for delivery and display.

The Lost Wax Casting Method History

The history of bronze sculpture dates back several thousand years, and was predominately used in Greece, Egypt, Rome and the Near Eastern civilizations. Many of the same techniques used thousands of years ago are still in use today, in fact.

Bronze is an alloy made by melting copper and tin in varying proportions, but the resulting metal is easily worked and melted, does not rust and has a smooth finish. The ability to be colored artistically using chemical treatment combined with the ease of use makes bronze an ideal medium for many artisans.

The earliest method of making bronze sculpture was to use solid masses of bronze, but later artisans developed the lost wax casting method, which enabled the artists of the time to develop larger works of art, and produce the bronze sculptures faster.

About a thousand years ago, artists began using the lost wax casting method to create their masterpieces, and has been used by such renowned artists as Donatello, Rodin, Remington, and Russel, to name a few. The process of lost wax casting allows artists to produce as many works of their art as they feel fit, and while no two pieces of bronze sculpture are the same, all bronze made from the same mold is still original artwork.

Many famous sculptures belong in the public domain, and can be recreated in bronze using the lost wax casting method process to put a piece of history in your home or landscape project, at an affordable cost.

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When two people are at one in their inmost hearts, they shatter even the strength of iron or bronze; and when two people understand each other in their inmost hearts; their words are sweet and strong like the fragrance of orchids."

- I Ching

How to care for bronze if the Statue of Liberty is bronze, why is it green?

Bronze alloys contain copper. When bronze oxidizes (comes in contact with water and oxygen) or rusts, the process causes the bronze to turn a green color. The Statue of Liberty is green - due to oxidation.

Once oxidized, this verdigris crystalline layer (called a “passivation layer”) actually protects, and seals the metal from additional corrosion. Hence, the Statue of Liberty stays green.

Go to historical parks such as Monument Avenue, in Richmond VA, Washington DC, Gettysburg PA, or NYC's avenues of art, you'll see that the bronze sculptures, of famous American soldiers, mascots, and even some fountains, are green. Other monuments are rich brownish bronze. The difference between the two finishes is whether the park has decided to preserve the bronze with wax, or let it go natural (‘verdigris”).

What is patina?

Today's bronze art objects come from the foundry with a chemical patina (green film). This protective layer changes the outside metal structure to prevent corrosion. Foundries may also add wax, lacquer, or urethane coatings to protect the valued warm bronze color.

How long does it take for bronze to get verd?

In direct sun, un-maintained and exposed to the weather, more than of 5-10 years (slightly shorter on the beach with salt water spray).

How can I let my bronze naturally turn verdigris?

Placing your mascot or statue outdoors will naturally cause it to turn green, verd or verdigris (green patina). Many people find this antique patina of green desirable, and may want to quickly customize their bronze using a tinted finish. Today, many foundries actually acid-etch the metal, to give the effect of antique verdigris.

How can I keep my bronze the same original color?

Simply paste wax your monument every year or coat with clear Permalac ?, urethane, or lacquer spray. What about white spots? When you first get your bronze, borax powder - used in casting - can look like crystals. The borax may be still in the metal, but not visible until it gets wet. If you see these crystals, simply wash them off, or clean with paste wax.

You may also see some white spots due to residual ceramic material from casting. Again, simply clean it up with paste wax, and touch up the color with Kiwi wax.

After bringing your bronze home, high calcium levels in the water often cause white spots, especially in fountains. This happens often in locations with heavy mineral content. Remove the spots using a good paste wax, and use de-mineralizing chemicals to treat the water. (Note: De-mineralizing agents can be found in most pool supply stores.)

What kind of paste wax is recommended for bronze?

Do not use automobile paste-waxes, as these will permanently damage bronze. Johnson's, Boston, or any non-abrasive, natural paste waxes are recommended.

For quick and shiny cleanups, use a spray-after-wash auto detailer that contains only wax.

Can I use tinted paste wax?

Some foundries use Kiwi shoe paste, which comes in brown, black, cordovan, and oxblood, to create a reddish-brown tint and add depth. This can be done at home. However, it's not advisable to use it where a heavy coat of wax has already been applied by the foundry.

How long does bronze last?

Almost forever! Archeologists are still discovering Greek and Roman bronze from the Mediterranean Sea, dating thousands of years ago. Interestingly, the very word verdigris comes from the word “verd” (Old French: green) and “di gris” (Latin: of Greece). These artifacts are still in good and identifiable condition.

How can I repair damage or scratches to my bronze?

For minor touch ups to your bronze art, refinishing kits, metal chemical patinas, and color-solvent dyes are available on the Internet (search under “bronze refinishing kits”).

Bronze is the mirror of the form; wine, of the heart"

- Aeschylus


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