The answer is simple, COST
A Cold cast bronze or brass sculpture would be a fraction of the cost of a bronze. There are several factors influencing cost, but as in most production processes it comes down to the basics, materials and labour.
The term ‘production’ might bother some, but it is the reality. Few sculptors have neither the facilities to make the often complicated molds required nor the facilities to melt bronze to 1700°F. Most often this is done in a foundry and beyond creating the original piece (not intending to diminish this talent) the artists contribution to the actual cast piece is negligible.
It should also be remembered few ‘bronzes’ are actually solid, they would be too heavy and very very expensive. Usually a bronze figurine with arms and legs will be produced in a number of pieces and then welded together.
If a bronze and a cold cast bronze of the same piece were placed side by side, it would be impossible to tell the difference, until you picked them up and then, perhaps the weight would be different, the cold feel of the metal would be indistinguishable.
Original clay sculpture, 2nd stage, by Michelle Caithness
Starting with the original sculpture a mold is made using silicone rubber. The number of pieces in a mold will be determined by the complexity of the art work, its shape and size. The design of any mold is critical to the success of the final casting. A mold for cold casting bronze needs to be as open as possible, when it’s separated into individual pieces.
While this mold may be complicated it will not be as complicated as its counterpart for a bronze, another fact effecting cost.
Cold Casting can be carried out in any studio, with basic equipment and skills, so the artist can have 100% input in the finished piece from inception to completion.
Epoxy resins are most suitable for cold casting, the outer metal skin is usually created with a ‘brushing gelcoat’
The metal powder is mixed into the gelcoat and then brushed onto the surfaces of the mold. Brushing gel coat will hold to the vertical surfaces of a mold, so an even coating of metal is achieved. Brushing in or painting any other metal filled resin will result in the metal powder pooling in the lowest parts of the mold and leaving the vertical surfaces bereft of metal.
Once all the surfaces have been coated, the mold is assembled and strapped together. Casting epoxy resin is then poured into the void until the mold is full and left to set. Demolding times will vary according to three criteria, room temperature, the amount of catalyst used and the bulk of the the piece. A small amount (1%) of shrinkage can be expected using this material.
In this process the piece will come out of the mold complete, arms and legs attached. The fins or join lines now need to be cleaned so as to blend into the surface. This can be done with traditional metal files and wet & dry papers.
At this point the only thing left to do is sit back and admire the finished item.
There are other finishes that can be used to enhance the piece, but they are all options. Coloured Wax or Patinas can be applied which will highlight detail, contours, texture and colours. High gloss or matt sealants can be applied as a final protective coating. No matter what finishes have been applied the best method for cleaning, should it be necessary is warm soapy water and a soft cloth, do not use detergents.
Finished Cold Cast Bronze with green waxing by Paradoxx