Solving bodycasting problems: air bubbles, fingertips and distortion

Bodycasting isn't technically difficult, but the mistakes you can make are always the same ones. Missing fingertips, pimples in the plaster, a distorted thumb: nearly all of it comes down to trapped air or too thin a layer of alginate.

Bodycasting with acrylic resin instead of plaster

The difference between working with plaster and with A1 Acrylic Resin is smaller than people think. There are two real differences:

1. Mixing. Plaster stirs to a smooth paste fairly quickly. Acrylic resin has to be mixed more intensively before it is smooth.
2. Moisture absorption. Acrylic resin absorbs moisture less readily. So mix the alginate mould with 3 parts water instead of 4. At 4 parts, water droplets escape from the alginate more easily, and you'll see them in the acrylic.

Once mixed, there is no difference between casting with plaster and casting with acrylic.

Small air bubbles, especially in the hands

These come from the resin itself, not from the mould. They are in it while you pour and rise once the resin is in the mould. Some reach the pouring opening and burst; the rest stay trapped against the inside of the mould and cure there.

The solution:

1. Mix the acrylic resin at the highest speed with a drill mixer or blender, until there are no lumps and the mass is homogeneous.
2. Take the mixing tub in both hands and turn it left and right alternately with a jolting motion. Keep repeating. That movement releases air bubbles from the wall.
3. Then tap the base of the tub firmly on the table. For at least a minute.
4. Set the tub down and repeat the left-right turning for another minute.

Let the resin flow gently into the mould when pouring. Hold the mould at a slight angle and let the resin run in along the wall. Once the mould is full, repeat the mixing steps with the cup: turn, tap, turn.

Missing fingertips

With acrylic resin this too is caused by air trapped during filling — not by using acrylic resin instead of plaster. The solution is the same as with plaster: tilt the mould while filling.

The full explanation, including the correct hand position to prevent trapped air, is in missing fingertips in bodycasting and the right hand position.

A distorted thumb

This comes from alginate that sat too thinly on the thumb. It collapsed, tore, or sprang back into the wrong place during filling.

If you take a container that is just too small, your thumb sits almost against the rim. A thin film of alginate forms in between. When you pull your hand out, you tear that film loose or rip it. During pouring the alginate springs back reasonably well, but not quite correctly.

The fix is simple: apply the alginate thicker, at least 7 mm. That gives the mould more body. Also helpful: press cotton wool into the still-liquid alginate before applying the plaster bandage. That creates a bond between alginate and support shell, keeping the thin alginate in place.

When to thicken?

Thickening the resin is only necessary if you are laminating or spreading it. For pouring it is unwise: the resin becomes less fluid and picks up less detail.

Pimples and bumps on the plaster cast

Pimples on the plaster mean there were air bubbles in the alginate. A few are normal and not a problem.

To prevent them: tap the bucket of liquid alginate firmly before the hands go in. That forces the bubbles upwards. Then put the hands in and rub the skin well so any bubbles release from the hand. Then hold the hand still until the gel has set.

Remove the pimples while the plaster hasn't fully hardened yet. It comes away easily then, with no need for sanding or hard polishing.

Making a cast of the chest or torso

Option 1 — the complete kit. The basis is the Pregnant Belly Bodycasting Kit. Do this with one or two other people; it needs brisk work. The included manual should be enough.

Option 2 — simple and inexpensive. Work with plaster bandage. Treat the cured plaster afterwards with a sealer; it seals the plaster and forms a film layer. Apply petroleum jelly to the skin beforehand, especially over chest hair — smooth it down against the skin with the jelly.

Casting a face with alginate

Always do this with two people. One lies down, the other mixes and pours.

1. Take a box roughly the size of the face, for example a shoebox.
2. Cut a hole in it slightly larger than the face.
3. Tape along the edges so the tape overhangs by about 1 cm. With the face in the hole, that tape seals the gaps.
4. Put balls of toilet paper in the nostrils so no material runs into the nose.
5. Take a tube to breathe through. Practise this beforehand. A drinking straw is far too thin; a yellow PVC pipe is usually ample.
6. Lie down and press the box firmly onto the face so everything seals all round.
7. Mix the correct quantity of alginate 3D-Gel with lukewarm water, using a blender.
8. Fill the box to the height you want.
9. Wait 5 minutes until the gel is firm.
10. Carefully lift the box, tube and all, off the face.
11. Pour the product you want into the mould within 4 to 5 hours.

Mix enough alginate in one go. If it turns out to be too little and the nose still protrudes, you cannot mix a fresh batch and pour it on top: it won't bond.

Little can be said in advance about the quantity needed; it depends on the box. Usually count on 2 packs of 500 grams, good for 3 to 4 litres of finished product. Always calculate beforehand.

Hanging a hand wreath

Drill a small hole very carefully and fit a screw. Start with a very thin drill bit and work up. You can secure the screw further with mounting adhesive or strong glue.

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Quantities per hand size are in plaster cast guidelines. All the materials are in our Bodycasting Kits. A question about your project? Get in touch.