This is an original technique I use for making portrait busts out of grout. Grout is like cement, except it is stickier and doesn't shrink. When cement dries it shrinks and tends to crack, which the grout does not do.
To make the finished bust lighter I use a mold to make crumpled aluminum foil cores. The cores can be bent some to give position variations.
The grout I use, "Keraset", comes in a light gray color. The grout can be given a variety of colors, depending on the addition of powdered pigments. The pigments are available in hardware stores for coloring cement. Right now, I am mostly making clay-colored grout using a combination of red and yellow pigments.
Step 1: The Mold
The 2-piece mold was made out of cement many years ago, and I don't have photos of its construction.
The core shape was originally sculpted in clay. Using mold-making techniques, I made a 2-piece mold of the shape.
The left and right halves of the core are molded out of crumpled aluminum foil. The halves are then taped together. The neck can be bent to provide position variations.