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 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.
Step 2: Packing the Mold Halves With Aluminum Foil
Since aluminum foil doesn't stretch, it will tear if you force it into the recesses of the mold. Tearing of the skin layer is avoided by first crumpling the aluminum foil to create a quilted pattern of wrinkles. That shrinks the area covered by the foil, but allows the foil to stretch out again without tearing as it is pushed into the mold.
I use a ball on a stick as a tool to help push the foil into the mold. Leave some excess skin hanging over the edge of the mold. It will be folded back over the crumpled foil in the middle to help hold it in place.
I usually fold up a pleated strip of foil and put it through the neck area to give the neck more strength when it is bent later.
Fill the skin with crumpled foil, fold over the skirt around the edge onto it and remove the core half from the mold.
Step 3: Join the Halves
Step 4: Coloring the Grout
Step 5: Mixing the Grout
I usually add the water first and then the dried powder. Stir with an old spoon, or other tool, or by hand, but you have to wear plastic or rubber gloves. I use "disposable" gloves, reusing them until they tear. The thin material almost lets you feel like you are working bare handed.
The grout can be mixed with varying amounts of water to give it thicker or thinner consistency. It all has its uses.
Step 6: The First Layer of Grout
Rub the first layer on with your gloved hand, or mini-trowel, such as a palette knife. It's quick and easy. I do a layer on the bottom of the core first and then set it down on a flat, non-stick plastic sheet to finish coating it. That way the bottom is plastered and out of the way. It has a flat and smooth surface when hard.
The plastic I work on is moisture barrier material used underneath cement slab floors in house construction.
Step 7: Sculpt the Bust
Unlike clay, which can be kept moist and pliable by preventing evaporation, the grout is in a continual process of hardening up once it receives water. It's always easier to add more fresh grout to the bust later than it is to carve away hardened grout, so try not to over-shoot your mark if you can avoid it.
Please excuse the unnatural colors of some of the photos. I don't know what causes my camera to go wacky on the colors at times. It's time for a new camera, I guess.