Creating a Bronze

Creating the Pattern

I. The first step in creating a bronze sculpture is to form a pattern for the the bronze to eventually be shaped into. Coming up with the inspiration for a design can come from many sources. A) With the images below Gibby worked with a customer to develop a design that would evoke the feeling and symbolism that they felt needed to be depicted for a veterans memorial. So Gibby visualizes in his mind the concept and begins sketching ideas. Usually 3 to 5 ideas are presented to the customer to choose from. B) After a concept is agreed upon, the research begins. Gibby is an artist that, with artistic flare, likes to be true to the details of the subject matter, and so he begins a quest for information and detailed reference material. In these photos Gibby relied on the expertise of his friend Steven Rubisch,  Marine Iraq war vet. He leads Gibby to accurate information, tells stories of his experience in Iraq and even poses in his uniform for an accurate depiction of US Marine paying respects to a fallen comrade. C) Gibby then begins to sculpt a miniature version, known as a maquette, of the sculpture to work out the design details to save time on the life-size version. D) After receiving critical tips from his expert friend, Gibby makes minor changes to the maquette and then begins to create the pattern for the Life-size version. E) Near the end of sculpting, Gibby has his expert friend come and evaluate the work, offer pointers and of course get his picture taken with the piece.  Final approval for the design comes from the customer is acquired, and it’s time to move on to creating the master molds.

The Master Mold

II. A) After the clay is finished it must be prepared for creating the master molds. This involves partitioning the clay sculpture into pieces so that the rubber can eventually easily be removed and offer the best wax castings in the next stage of the foundry process.  B) The master mold covers over the sculpted pattern to make the design that each piece in a limited edition bronze follows. Silicone rubber is used to create the master molds of a piece. The rubber comes in liquid form, but a catalyst agent is added to the rubber to get it to solidify. Before the rubber is solid the mold maker brushes a layer onto the clay sculpture. Then the rubber is allowed to set up.  C) This is done at least 4 to 5 times and often there is a layer of mesh incased over the surface of the mold into the third coat of rubber to extend life of the mold and give it strength. D) Rubber registrations seams are strategically added after the second coat of rubber so that the mold may later be removed from the original sculpture and then fit back together exactly the same as if the clay was still inside. E) Before removing the rubber from the clay, a ridged mold (either plaster, cement, fiberglass etc. mixed with some kind of fiber), covers over the rubber mold to help maintain the proper shape. Very often the ridged molds have tabs created right into the edges to later accommodate molds, that hold the pieces of the mold together.  F) After the ridged mold has fully hardened, holes are drilled into it’s tabs to create a space for registration bolts. G) The ridged mold and the rubber mold are then be removed from the clay. H) The rubber and ridged parts of the mold are reassembled together and bolts are added to hold the molds together. The rubber and ridged molds at that point become the master mold for creating all of the bronzes within an edition. Gibby never redoes his molds to extend the life of his editions, making them very exclusive.

The Wax

III. A) Using the newly created master mold, an expert wax pourer prepares the rubber to create the wax pattern. The rubber mold is removed from the ridged mold and heated up to help to improve the flow of the melted wax as it is being pour. B) The molds are then reassembled while the rubber is still hot. C) An expert wax pourer pours the wax into the mold at an gradual declined angle to avoid splashing. D) The mold is the rotated around and gradually tilted forward to slowly empty the wax out of the mold. This technique offers optimal coverage of the wax to the interior of the mold. E) The wax is then allowed to cool down. F) Without heating the rubber again, this technique of covering the interior of the mold is repeated 2 to3 more times to create a approximate 3/16 thickness to the walls of the wax. G) After the final coat of wax thoroughly cools down the molds are disassembled again to remove the, now cooled, wax pattern. H) Any bubbles or seams that developed in the wax pouring are then fixed so that wax pattern reflects the original sculpture. I) Wax patterns often are cut to open up air ventilation into the piece for the ceramic making process. H)To create a gating system in which the bronze will eventually be able to flow fill the mold, wax bars, called sprews are strategically attached at various places within and sometimes out side of the wax pattern. All of the sprews come to one point where a flat surface is created by melting on a hotplate. The flat surface is to accommodate the attachment of a wax cup,

The Ceramic Shell

IV. A) With the wax pattern and the sprew system completed, the wax form moves on to have a ceramic shell created around it. This is done first by dipping the form into a mild acid bath that both cleans and etches the surface of the wax. This process helps to reduce bubbles from forming into the mold. The molds are rinsed again with clean water to remove the acid wash. B) The wax form is then dipped into a ceramic slurry and then allow to drain excess ceramic material back into the tank. C) A coat of very fine sand called Zircon is used to cover the interior and exterior surface of the wax form before the ceramic slurry dries. The form is then placed on a rack to stay until the entire surface is thoroughly dried. This process of dipping into the ceramic slurry and then covering with sand is repeated at least six more times while increasing the coarseness of the sand for the second and third dips. A final dip is done into the slurry that doesn’t involve coating with sand afterward. This is the called the clear coat. In all, a piece will receive a minimum of eight dips of ceramic. This process takes day to a week depending on the amount of airflow applied during the drying process. D) The final portion of the ceramic mold preparation involves cutting a large hole into the bottom of the now ceramic cup that was formed over the wax cup. E) Using a small torch the wax in the cup is melted out.

The Wax Melt-out

V. A) To create the vacancy needed to accommodate the bronze into the ceramic molds, the wax that created the ceramic pattern must be removed. This is accomplished by melting the wax out at high temperatures. A burn-out oven is heated up to 1500 degrees F in preparation to insert the ceramic molds. B) When the oven is up to temperature a foundry worker, wearing protective clothing, inserts the ceramic molds into the oven with the open cup facing down over drainage holes in the bottom of the furnace. The wax is melted out quickly at high temperatures to prevent cracking in the ceramic due to a slow expansion of the wax. C) After all of the wax has drained from the ceramic molds a foundry worker retrieves the melted wax and measures it to determine the amount of bronze needed to fill the castings. D) An assessment is made about the integrity and strength of the shells based on the effectiveness of the wax-melt prior to casting the Bronze.

The Bronze Casting

VI. A) While the ceramic shells are melting out the wax, bronze is being melted down in a blast furnace and crucible. When the crucible has been filled to the proper lever foundry workers use large tongs to remove the crucible from the furnace, and the set it into a casting cradle and lock it into place with a spring-loaded lever. B) One of the foundry workers uses a pyrometer (Hi-temp thermometer) to measure the bronze for ideal casting temperature. C) When the optimal temperature has been reached, one worker removes the ceramic shell from the melt-out furnace and set them into place to receive the bronze an two workers lift the casting cradle and pour the melted bronze into the empty shells. D) The bronze casting cools for about a half hour before removing it from the rack. E) After the bronzes have thoroughly cooled, using percussion tools the ceramic shells are broken away from the new bronze castings. F) Using grinders or a plasma cutter the bronze sprews are removed from the bronze castings and can be recycled for the next set of castings. G) Each of the castings is then fully chipped out and sandblasted to prepare for assembly.

Assembling the Bronze

VII. A) Usually bronzes cast into more than one piece that need to be assembled together after casting. Each of the pieces get fitted and welded back together. This may involve simply reattaching a part or it may involve heavy bodywork using sledge hammers, chains, cargo binders and hydraulics. B) Each of the welds are then ground down using angle grinders and nematic die grinders. C) Also using more grinders and sanders, the sculpture’s original texture patterns are replicated back into the welds. D) The piece is sandblasted to reveal  any flaws in the surface of the bronze. E) The piece is check over for flaws and any flaws are fixed.

The Patina

VIII. A) Patination of a sculpture is basically the process of adding color to your sculpture. This is usually achieved through the use of chemicals and pigments abruptly being evaporated onto the surface of the bronze. Some patinas simply have a chemical reaction upon application. Also various abrasive are used to achieve different effects. There are innumerable ways to create patinas and many variations on those patinas. No two are exactly the same. Most often patinas involve using large torches to heat the patinas in order to properly except patinas to the surface of the bronze. B) Sealing a patina is critical to lock the colors into place and to protect the patina from wear and from the elements. Most often the bronze needs to cool down prior to the applying the sealant, but some require the bronze to be hot. Most sealants are various types of lacquer and or wax. C. If a wax is applied, the bronze can be buffed to the desired sheen.

Basing, Felt, or Installation

IX. A) The final touch on a bronze involves what goes underneath the bronze. If the bronze will be shown indoors, they can be mounted to a wood or stone base with felt glued to the bottom to protect furniture, or just have felt with no base. With a stone or wood base, a turntable may be attached to help the sculpture to easily rotate. If it is an exterior piece, it may also be mounted outside using anchor bolts, and epoxy or cement.