Full Process Casting

We are a Full-Service
Bronze Foundry

Our Process

Learn about our ten-step process to see how a bronze statue is created.

The lost wax process (also called investment casting) is an ancient method for making metal objects, particularly sculptures and intricate metal parts. This technique has been used for thousands of years and is still widely used today for fine art castings. We continue to master this process to achieve EXCELLENCE IN EVERY CAST.

Explore The Process

3 Lost Wax Process

The Lost Wax Process

  1. Mold. A mold is created.
  2. Wax Pour. Wax is poured inside the mold creating a wax model.
  3. Wax chasing. The wax is removed from the mold, cleaned up, sprues or gates are added along with a pouring cup to the wax model.
  4. Slurry or Investment. The wax model and sprues are dipped into a slurry material to create a ceramic shell.
  5. Flashing or Burnout. The shell is placed in a kiln.  This creates a ceramic shell and melts out the wax, creating a void for the bronze to be added.
  6. Casting. Molten metal is poured into the mold.
  7. Chip-off. The ceramic shell is cooled, then chipped off exposing the metal.
  8. Metal Prep. The piece is sandblasted, and the sprues are cut-off with a plasma cutter.
  9. Metal Chasing. The piece(s) are welded back together, and the final polishing and texturing is completed over the welded seams. Final polishing takes place.
  10. Patina. The desired finish is applied.

Sculpting

A sculptor may create their original artwork out of various materials (clay, wax, wood, plaster, stone, etc.), but the most common medium we see is clay.

Artists will spend considerable time studying, mapping out, drawing, and designing a sculpture long before any sculpting actually begins. Depending on the size and complexity of the piece, sculpting can take anywhere from days to months to finish.

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Mold Making

After an artist's original piece has been sculpted, a silicone rubber mold must be made.

Layers of liquid rubber are applied to the original sculpture to capture the fine detail. After the rubber has set, a thick plaster mixture is applied and given time to harden to create a rigid "mother mold" to help preserve the firm shape.

Depending on the size of the piece, a mold can be made in several pieces to allow for a more excellent wax pour and ease of assembly.

Wax Pour

Now, using the rubber mold made from the original piece, molten sculpting wax is poured into the hollow interior of the mold. The wax is allowed to cool before it is carefully pulled out of the mold. Now we have a highly detailed positive wax copy of the original sculpture!

Wax Chase

Now that we have a detailed wax copy of the original sculpture, our trained wax chasers now clean up the wax.

Using many of the same tools that the artist uses to sculpt the original, our wax chasers clean up air bubbles, seams (from connecting areas of the mold), and any imperfections so as to match the texture and essence of the artist's original sculpture.

Slurry/Shell

The sprued wax copy & cup are then dipped in several layers of a liquid "slurry" mixture and sand to encase the wax, which then dries and hardens. This ensures that the wax pattern & sprues are fortified by an outer ceramic shell that becomes the final mold after the shell is fired and the wax has melted out.

Bronze Casting

After the ceramic shells have been hollowed out, ingots of bronze are placed into a crucible and melted into a liquid state. The red-hot crucible is hooked to a movable crane and hoisted up to pour the molten bronze into the ceramic shells at 2000 degrees.

Metal Prep: Chip, Sandblast, & De-sprue

After the molten bronze has cooled, the ceramic shell is removed through chipping and sandblasting to reveal the detailed, raw bronze copy of the original sculpture.

The sprue gates that were attached in wax (now converted to bronze) are cut off so that the metal chasing can begin!

It is more common that a sculpture is cast in several parts, so our metal chasers will prep and weld the pieces together before beginning the metal chasing.

Metal Chase

Once the metal has been prepped, our metal chasers re-assemble the art piece by welding the cast pieces together. Then, significant time is taken to chase away the weld and replace the texture in the sculpture. Pneumatic tools are used to restore detail, resulting in an exact representation of the artist's original sculpture.

Patina

The final stage is patina, which is the coloration of the bronze brought about by the oxidation of the metal surface. This is achieved by applying various chemicals and finishes to the surface of the bronze to ensure they create the desired color effect that the artist desires.

Caring for your sculpture

Overall Info
Caring For An Indoor Bronze Sculpture
Caring For An Outdoor Bronze Sculpture

Overall Info

Its important to know that bronze is about 95% copper (depending on the alloy). Copper turns green because of an oxidation reaction; that is, it loses electrons when exposed to water and air. The resulting copper oxide is a dull green. You’ve probably seen a copper penny turn green when left in water over time, or a public statue fade with a green tint. One of the most famous examples is the Statue of Liberty. Originally it had a shiny orange-red copper color, but because of the moisture in the air, it quickly oxidized into its famous green color. The important thing to remember is that all bronze darkens as it ages, but by with proper care of the surface of your sculpture, you may be able to slow this oxidation process for a time.

Depending on preference, some people really like the look of an aged bronze, while others prefer a fresh, new patina look. The surface of your bronze can be cared for using the following steps below, but unfortunately over time there is a natural oxidation process that must occur.

There is always the option to put on a new patina to any bronze sculpture. The surface is “sandblasted” using high- pressured sand and air to remove the patina finish, allowing for a new patina to be applied. If you would like a piece “re-patinaed”, feel free to contact us!

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Caring For An Indoor Bronze Sculpture

Cleaning and waxing an indoor bronze sculpture at least once a year is recommended, possibly twice a year in humid or corrosive environments. Never use spray or liquid furniture polishes to dust or clean a bronze sculpture as many of these products contain oils that can soften initial wax coatings, thus darkening lighter patinas and/or removing the protective finish.

Cleaning your bronze sculpture:

1. Using a soft, clean cotton cloth, gently wipe the surface free of any dust and fingerprints. We recommend cleaning deeper crevices with a 2-inch paint brush (the cheap “chip” brushes work great for this). Wrap the metal ferrules of the brush with some masking tape to avoid scratching the patina while dusting.

2. Using a new 2-inch Chip Brush and a can of Johnson Paste Wax (you can buy this at Home Depot or Lowes), lay the bristles of the brush across the wax surface back and forth in a sweeping motion. One or two strokes should do it, you really don’t want to overload the brush with wax (especially with Johnson Paste Wax), that will result in a longer drying period and possible wax buildup. There is a possibility that too much wax can harm or even destroy a patina. Therefore, carefully put a super-thin coat of wax on the surface of the bronze in a gentle sweeping motion. Gently work the brush down into the crevices as you apply the wax. Over-waxing a bronze patina can shift and remove pigments suspended in waxes originally placed on the surface as part of the patina.

3. You will be able to tell where you have waxed as the surface will be matte and not shiny. Continue waxing until the entire surface has been covered. Wait about 30 mins until the wax has completely dried.

4. Using a clean, dry cotton cloth, begin gently rubbing the surface of the bronze until the desired shine appears. Work the cloth in a circular motion on the large smooth ares of the surface. If you would like to keep the matte look, you can forgo this final buffing step.

The following is a list of commercial household products that should never come in contact with the patinaed bronze surface:

  • Bleaches
  • Oven cleaners
  • Glass and porcelain cleaners
  • Any other strong or weak cleaning solvents
  • Steel wool and scouring pads
  • Vinegars
  • Plant fertilizers
  • Furniture polishes

Other liquids in the form of beverages found in the household which are damaging when they come in contact with patinaed bronze are:

  • Alcoholic beverages
  • Soft drinks
  • Citrus fruit juices

For more information or tips on caring for your bronze sculpture, we recommend the book “The Care of Bronze Sculpture: Recommended Maintenance Programs” by Patrick V. Kipper

Caring For An Outdoor Bronze Sculpture

For any outdoor bronze sculpture, we highly recommend contacting the artist, gallery, or even foundry that cast the piece to determine the best maintenance program for your specific piece. The following are general cleaning instructions and should not be used without further consultation.

The best time to clean and wax bronze sculpture depends on whether it has a light, dark, or multi-colored patina. It is recommended to choose a clear warm day in spring and again in fall. For a dark or light patina, we recommend cleaning in the heat of the day, allowing time for the bronze to dry. Multi-patinas, or those patinaed surfaces that contain more than one patina or color, should always be waxed carefully in the cool of the late afternoon.

Since maintenance programs for outdoor sculpture deal with larger surfaces than those normally associated with indoor care, waxing a cool bronze surface may take more time as it is advisable to apply, let dry, and buff these large surfaces in small sections.

Cleaning your bronze sculpture:

1. Rinse the surface of the bronze sculpture with clean running water. Pay particular attention to places in textured surfaces that collect and hold water.

2. Use a mixture of non-ionic or neutral detergent and water to clean the surface of the bronze. Most janitorial supply stores carry a line of neutral detergents. It is always best to follow directions for recommended concentration mixtures which are usually found on the detergent bottle’s label. It is never recommended to place concentrated detergent directly on the surface of the bronze, but rather, to mix the appropriate amount of detergent and water in a non-metallic bucket first.

Begin washing the surface down using a soft non-metallic scrub brush, gently working in a circular pattern. Rinse the surface of the bronze regularly to ensure that no loosened particles have been washed into lower lying areas of the bronze. Start washing and rinsing the surface from the top or upper-most part of the sculpted surface and work downward.

3. Allow the surface of the bronze sculpture to dry in the sun. Towels may be used to help soak up water remaining in low lying areas of texture. It is most important that the surface of bronze be very dry prior to waxing.

4. The waxing stage is where we highly recommend that you consult with the artist or casting foundry before proceeding. Many outdoor sculptures may require a more specific up-keep program than just waxing. If waxing is recommended in a consultation, as a general rule, you can follow the same waxing instructions listed above for an indoor sculpture.

5. After the wax has dried, use a clean, soft cotton cloth and wipe the surface in a circular pattern to compress and shine the dried wax. Be sure that recessed ares of textured surfaces are waxed and buffed as well.

Again we highly recommend consulting with an artist, gallery, or casting foundry before cleaning an outdoor bronze sculpture. For more information or tips on caring for your bronze sculpture, we recommend the book “The Care of Bronze Sculpture: Recommended Maintenance Programs” by Patrick V. Kipper