How to Copy a Monumental Sculpture Using 3D Technology- Part 2
FROM THE ARTIST’S STUDIO
Bridgette and her interns paint rubber on the many pieces of the Grambling Tiger. Over all the rubber they create a mother mold. This mother mold is made with fiberglass.
For Bridgette Mongeon, who is working on the sculpture of Booker T. Washington, finding ways to reproduce large and small pieces using digital technology and traditional fine art was the inspiration for her book. The thing about working with technology is that it is always changing. Going to bronze casting from 3D print is trickier than it seems. Bridgette documents her process and, in her book, focuses on recreating the Grambling State University Tiger. To understand how tricky going to 3D printing to bronze casting can be, let’s look at the bronze process. You will see this in more detail later as she works on the sculpture of Booker T Washington. But here is a quick primer.
Inside each of the pieces of mold the foundry will paint or pour wax. When you see a bronze it is only as thick as this wax- usually about 1/8- 1/4″ thick.
Lost Wax Method of Bronze Casting
When a sculpture is completed and approved by the client, it must go through many parts of a process that is called “investment casting” or “lost wax bronze casting.” Bronze casting is an ancient process that has changed little over the years. Here are the steps.
1 Mold
First, she will make a mold. A mold can have many parts. For example, Alice In Wonderland sitting in her chair was approximately 20 mold pieces. When making a mold, the artwork is normally destroyed. Sometimes the artist does the mold other times the foundry does this step. It is often difficult to ship a large clay sculpture to a foundry. In that case, the artist or foundry will create the mold in the artist’s studio, and they ship the mold pieces to the foundry.
The clay of the Grambling tiger head and the wax. The artist removed the fangs to be able to pour make the mold.
2 Wax
The artist sends the mold to a foundry where they will pour or paint a thin layer of wax and gate or sprue up each wax. The gating of the wax helps air and gasses to move out and metal to move into a piece when the pieces get to pouring.
3 Slurry
Then, the wax goes through a slurry where the pieces are dipped in vats covering each piece with a layer of ceramic shell both inside and out.
The foundry creates a pour cup as well as gates or sprues. These will help the gasses escape and allow the metal to pour.
4 Burn out
The shell is then baked and the wax is removed.
5 Pour
The metal is poured into the shell.
6 Chasing or finishing
Once the metal cools, the shell is broken away, and the many pieces are welded together.
7 Patina – This is the coloring of the metal
What is mentioned above is the “traditional process of investment bronze casting.” But what if a sculpture could be 3D printed and go directly to investment casting? That means that step 1 and 2, could be avoided all together. These are costly steps, but at the same time so is 3D printing something at a large scale.
Each of the pieces is dipped to create a ceramic shell both on the inside and outside.
Bridgette has vendors that are like herself. They have risen to the challenge of exploration in the combination of traditional and digital processes. She does have a vendor who can 3D print “Lifting the Veil” in detail with high resolution at the size that Booker T. Washington High School would like, and she also has a vendor who already has been 3D printing FDM. (See description of FDM in post about 3D Printing.) This foundry has been printing 3D pieces and burning them out (step 4.) The vendor she has to 3D print will be doing so using SLS and a high resolution print that is then dipped in wax. (See description of SLS in post about 3D Printing.)
The wax is burned out of the ceramic shell in a very hot oven.
The Booker T. Washington project prompted a wonderful conversation between each vendor and the artist. They had to discuss details like the temperature of the burn out for the 3D print, residue leftover in the investment from the material, safety issues cost, and more. But, now her “go-to foundry” and her vendor for 3D printing are recreating artwork using SLS, all because of the possibilities and challenges that presented itself in the possibilities of recreating the sculpture “Lifting the Veil of Ignorance” using digital technologies.
Note: you can 3D print in many different substances, including glass, paper, and ceramic. You can find many of them on service bureaus like Shapeways or i.materialize. In the past, Bridgette has printed directly to bronze. This means the 3D printer prints in bronze. Printing directly in bronze is very costly and not done on larger pieces.
Pouring bronze in the shell.
Questions
Do you know what metals are in the traditional bronze?
What percentage of each metal is in a bronze?
How old is the lost wax method of bronze casting?
Have you heard of “The Bronze Age”? When was that? Why did they call it that and what does it have to do with bronze?
Author Sculptor Bridgette Mongeon
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