Making A Brush-On Polysulfide Rubber Mold Of A Masterpiece
This is a continuation of a photo sequence that chronicles the mold making process for casting a da Vinci horse design that was never realized while the great master was still alive. To read the full story, see "Finishing da Vinci's Unfinished Masterpiece" listed under the 'Sculpture" gallery on this website (look for the gold horse in the caption).
FMC® Polysulfide rubber was used to make the mold of this model because the original model was sculpted in Roma Plastalina, a sulfur bearing modelling clay. FMC® Polysulfide rubber is not inhibited by sulfur which is present in modeling clays preferred by sculptors. No sealing agent or release agent was necessary prior to applying rubber to this model. Cured rubber is soft, stretchy and perfect for casting wax as part of the lost wax process that will ultimately result in the piece being rendered in bronze.
FMC® Polysulfide rubbers are also archival, meaning that the molds will last many years in a mold library.
1 - This da Vinci horse maquette was sculpted in Roma Plastilina
2 - 100 parts of Part A of the polysulfide compound is weighed out.
3 - 12 parts of Part B is weighed out.
4 - The FMC®-200 is carefully mixed 100A:12B.
5 - The initial layer is the ''print coat'' or detail coat and is applied thinly. The rubber is easy to apply and goes on smoothly.
6 - Special attention is paid to the deep detail of the horse's mane with care being taken to work the rubber into the detail.
7 - The FMC® rubber is applied to all surface area. The rubber is easy to apply and goes on smoothly.
8 - The initial layer is allowed to become tacky before subsequent layers are applied.
9 - 3 heavier layers are applied with time allowed in between each layer to allow the rubber to become tacky. Parting shims are incorporated in between layers 3 and 4.
10 - Plaster support shells are carefully applied.
11 - Care is taken to avoid mechanical lock between shell segments.
12 - After all shell segments have been applied to the body, the final segment is applied to the horse's face.
13 - With the support shell finished, the next step is to let all materials cure prior to demold.