Written by Daniel Mariotti
Photographs by Daniel Mariotti
Wax is usually the 2nd major step in the casting process. From rolling, dressing, and gating; in this blog, we will briefly go over what these steps are in the Wax Department.
Wax is the process where we create a positive from the mold made off of the original.
Before starting any project, we document it to easily reference the projects we have in queue and what stage of the wax process each project is in.
When we receive a mold, we verify that all the molds for the sculpture are accounted for. Many sculptures have multiple molds that will eventually be combined to create the final product. We make sure the molds are labeled, cleaned, and sprayed with a release agent so the wax will release from the rubber molds with ease. We then assess if there are any areas of high texture that may need to be painted in before the mold is closed up for rolling. “Painting in” ensures that hard-to-reach, high or deep textures get thoroughly coated with wax.
As we close up the mold we make sure all keys are seated correctly in the mother mold to prevent the form from slumping and dimpling and that the seams come together perfectly, minimizing the dress time.
Next, we prepare the mold for rolling by assessing if it needs a cap. When a mold has openings on either side, one side needs capping to keep the wax inside the mold so we can “roll” it around, building up the needed layers. The cap is a piece of thin cardboard cut in a shape slightly larger than the opening. We dip it in wax, release it and staple it to the rubber of the chosen opening, sealing it with wax to prevent any leaking. At this point, the artisan will “pull” the waxes out of the heating pots by pouring wax into buckets to cool to the correct temp for rolling.
While the waxes are cooling an artisan will heat up the rubber inside the mold. Warm rubber ensures less bubbling will occur in the print coat, leading to a better surface on the wax sculpture and less possibility of delamination between layers of wax. Further prep for “rolling” involves spreading a thin layer of water on the floor to help with clean up. The rolling team will stretch and put on back braces to prevent injury. When needed, the team will use one or two of our hoists to help mitigate the weight of the mold.
When rolling it is always important to visualize the cavity, taking note of any “knife edges” where the wax may run off leaving a thin spot or any hidden cavities where wax may get stuck creating thick or solid spots.
A successful wax is made up of 3 to 4 layers of different temperature wax. The first layer is the hottest and is made using our red print coat wax. The wax should be flamed over with a torch prior to pouring to burn off any bubbles and should be poured slowly and gently to ensure the least amount of turbulence. The second coat is made with the same red wax and acts as a backup print coat, ensuring an even and thorough surface. This second layer should be poured a little cooler and can be rolled more vigorously. The 3rd and if needed 4th coats are made with our “green” reclaimed wax and are poured cooler and thicker still. Their main goal is to achieve our desired thickness of ¼ in. After these coats are rolled we use a tool to measure the thickness on every side to ensure quality and desired thickness. The mold is then set aside to cool. If needed, we will add wax or wooden dowel braces inside the waxes while they are still inside the mold to keep waxes from warping as they shrink while cooling.
Once the waxes have cooled to room temp we remove them from the mold and take a close look at the surface and overall thickness. If the wax is not close to perfect we re-roll it to cut down on dress time. In the event that a “good” wax has an uneven thickness in areas, we can thicken or thin out the problem areas. For areas that are too thin, we add extra wax, heating the existing cool wax with a torch before we apply hot wax. If an area is too thick we scrape away the excess wax leaving the desired ¼ in thickness. Once even thickness is ensured we begin to dress the wax.
Dressing the wax involves removing any visible seams left behind by the mold. Filling or removing any surface imperfections like positives or negative bubbles. We fix any distortions in surface texture and form that may have been caused by the molding or de-molding process. We use a variety of tools, heat, tricks, and techniques to mimic the existing textures. Once complete, all imperfections removed and form restored, we finish the surface with a buffing agent to remove tool marks and restore the surface to look as though nothing has been done. A well-dressed wax should show no sign of ever being touched by mold or artisan.
At this point, if the piece is part of a group, we fit each wax in the group together to make sure they all fit seamlessly. Once this has been established, the wax is put into an etching solution to remove any buffing agent or oils still present on the wax surface.
When the wax is as close to looking like the artist’s original as possible, photographs are taken for the artist’s approval. The artist will give any corrections and once these are applied to the wax, we finish dressing by applying “disclosing wax” which fills any tiny pinhole bubbles remaining on the surface. Now the wax sculpture is ready for the next step, gating.
Preparations for gating are many and vital to the steps that come after. Our gating systems are designed to ensure the best possible metal circulation for pouring. We cut patches out of our waxes so that the ceramic shell can dry thoroughly between coats, limiting the amount of work for the metal chasers. We must also make sure our patches are as hidden as possible and our gates are in areas that will not create casting flaws. Everything we do in the gating process can and will affect the subsequent steps.
Gating is the wax circulatory system we add to our sculpture to allow the metal to flow into our casting and the air and gasses to flow out. There are two main types of gating systems, direct and in-direct. Here at Bollinger Atelier we mostly utilize the in-direct system, but every piece is assessed and an individual gating system is designed for each. All gating designs consist of a “cup”, “down sprue”, “gates” and “vents” all built around the wax sculpture. Each system is suspended from a metal hook or bar depending on the size and weight of the wax.
Once a gating system is complete we weigh it to establish the entire wax weight. This number is written on the wax cup along with the type of metal and the temperature at which the metal is to be poured. The wax weight is needed to calculate the exact amount of metal to be melted to fill the casting.
The wax process is now finished and the gated wax sculpture is passed onto the next step in the process. Ceramic Shell.