Page 50 - BSAM 2016 Q4

...another method is necessary if
the base of the stone has a complex shape, for example, indents, crevices or holes.
1^
1%
1% I mentioned at the start of the article that an- other method is necessary if the base of the stone has a complex shape, for example, indents, crevices or holes. With such a base, the plaster would ow into these areas and simply grip the stone in a way that you could not remove it from the mold. In simple cases, you could ll the holes or indents in the bottom of the stone with plasticine so that the plaster will not ow into those parts, but another good way to get your indented impression is to use orist foam.
1^ Press the base of the stone rmly into the foam block down as far as you would like the recess to be and then very carefully remove it to reveal the complex shape. Be careful not to break away the edges of the foam when removing the stone. You want to preserve the sharp edges for your outline.
Using foam is a little more di cult because of the so ness of the material when taking markings and especially when inserting the cotton tip markers into the foam mold, however, it is an accurate way to get your recess if you are careful.
Whichever method you use to create a mold of the stone's bottom, if you have been accurate with your outline and depth markings, you should nish up with a perfect, or near perfect recess for you stone. If you make any small errors with the internal carving you can always use a little wood ller to make corrections.
* Perspex is a trade name for Acrylic or acrylic glass , a transparent thermoplastic that goes by other trade names; Plexiglas, Acrylite, Lucite, and several others.
48 | BCI | October/November/December 2016