Plaster cast sculptures are among the easiest to make. A semi-pliable mould of an object is created from a medium like clay or alginate. When the object is removed, an impression is left behind. This is then filled with liquid plaster, which is allowed to harden before being removed. The results are startling in their lifelike appearance. Many people new to this type of art start by creating a mould of one of their hands using plaster. Even beginners can make professional-looking sculptures this way. The plaster captures every fine nuance of the hand, including fingernails or jewellery with remarkable detail.
Pour 2 cups of dental alginate powder into a bowl. Mix with an equal amount of water and stir well. Add additional water, a little at a time, until the consistency is very smooth.
Pour a small amount of alginate into the cup to a depth of 1 and 1/2 inches. The hand being cast should be inserted into the cup, well centred, so that neither the bottom nor the sides of the cup are being touched. Pour the prepared alginate mixture into the cup around the hand, stopping one inch below the top of the cup.
Begin preparing the plaster of Paris mixture according to the directions on the label. Wait 12 to 15 minutes for the alginate in the cup to set. Gently remove the hand from the cup, revealing the depression left behind. Quickly pour in the plaster mixture, filling the depression completely and the cup to the rim.
Let the cup remain undisturbed for 12 to 18 hours. Invert the cup, cut or tear it open at one side, and peel off the alginate and the rest of the cup in fragments. The plaster cast sculpture of the hand will emerge.
Spray the sculpture with clear acrylic or paint it. If you choose to paint it, flesh tones are especially striking as they cause the plaster hand to look even more realistic.
Many people prefer to remove jewellery such as rings before inserting their hand into the cup of alginate. If you would like to leave them on in order to have an impression of your jewellery preserved in the finished plaster cast, apply a thin, protective layer of petroleum jelly to your ring before inserting your hand. This helps prevent small amounts of alginate from being stuck in the ring setting. Cleaning your rings after the project will then be easier. After the alginate is poured around the hand, the person whose hand is being cast may sit comfortably as long as the position of their hand in the cup doesn't change.
While the alginate is setting around your hand, try to keep it as still as possible. Any movement of your hand at this point will prevent the alginate from moulding closely and will distort the shape of your hand in the finished casting. For the most lifelike results, try to relax as much as possible in order to avoid moving the hand being cast.