Casting Methods & Materials
No matter what casting material is chosen, the following process applies to all of them:
After the clay model is made, a silicone mold is made from this model which becomes the exact negative. A supported casing also called the outer mold is built around it, which supports the inner silicone. Most molds are at least two pieces with shims and keys that are placed in strategic locations around the trim of the mold so that the mold can be put together accurately. On larger models, multiple mold pieces off the model are often made. Once these steps are taken, the mold is ready to accept the casting material.
Casting materials offered are:
Bronze ~ White Marble ~ Fine Concrete ~ Vinyl Composite ~ Resin ~ Fiberglass
Molten wax is poured into the mold and swished around until an even coating is established. This hollow wax copy of the original model is removed from the mold and using heated metal tools is hand tooled (chased) to rub out marks left from the parting lines where the pieces of the mold came together. This method cleans up any imperfections making the wax copy look like the finished piece. Sprungs are then added to the wax copy, these are paths that will allow air to escape while in the molting casting process. The sprued wax copy is then dipped into a slurry of silica and is left to dry creating a ceramic shell-coated piece. This shell is then placed into a kiln whose heat melts out the wax which runs out. All that remains of the original model (artwork) is the negative space formerly occupied by the wax, inside the hardened ceramic shell. The vent sprungs (now tubes) are also hollow. Metal is then melted in a crucible in a furnace then carefully poured into the shell. The filled shells are now left to cool. After its cooled, the shell is hammered away, releasing the rough casting, the sprungs (tubes) are also recreated in metal but are then cut off. Just as the wax copies were chased so is the metal casting, removing any imperfections and filling in any air pits or bubbles that occur during the casting process. The bronze statue is now polished and the patina is added to give the color tone. The final step before delivery is a wax coating (such as Johnson’s Wax) that is hand-polished all over the statue.
* Maintaining the beauty of a bronze statue:
The best recommendation is to keep the statue clean of debris and to wax the statue at least twice a year to maintain a barrier between the metal sculpture and the elements (weather, water, UV lighting rays to name a few). Keeping the statue waxed is also the best bet to removing graffiti should the unfortunate happen because the graffiti will be on the surface of the wax rather than on the surface of the actual metal. Continuous maintenance may slow down the natural patina aging process (turning green) but unfortunately there is no stopping it especially if the statue is installed in an outdoor location.
A blend of fine grade white marble powder and specialized marble resin are mixed together under proprietary supervision which is then weighed out accordingly for each mold (model). The material, as a liquid state is then catalyzed (hardener) and within minutes is poured into the prepared mold that has been securely set upside down with its pour-hole upward. For most statues or artistic articles a mold is hand-poured full, meaning the statue is solid. It is not poured in a slush motion. Once the material has solidified, the mold is opened revealing the casting. It usually takes one full day for the casting to be considered fully cured before the chasing can begin. Removing casting lines, imperfections and any bubbles that occur during the casting process is at this point all done by hand using both sandpapers and small hand sanding tools for ease. Once perfected, the casting is hand-cleaned to remove dust, lightly polished using soft cloths to bring out the natural sparkle of the marble. That’s it…the casting (statue) is beautiful.
If the casting has been ordered with a patina, the same process above applies except instead of polishing, the patina is hand dry-brushed onto the surface and then very lightly sealed.
White marble castings can be used for both indoor and outdoor placement, however patina covered castings are not meant for outdoor use.
Maintaining the beauty of a white marble statue is very easy. Because of its non-porous any cleaning agent or detergent can be used with water. For a more aggressive cleaning to removing ink or hard to clean spots, acetone can be used with ease. Even a light sanding of the surface where a hard-to-clean spot is can be done; you’d be amazed at how easy yet how durable MARBLECast is.