For 500 years, art students from Michelangelo (early 15th century) through Sargent (late 19th century) were taught to draw by copying classical sculpture from ancient Greece and Rome. When it was not possible to travel to see these original sculptures, art students copied plaster casts of the sculptures, which is why today we call traditional academic drawing of sculptures "cast drawing".
I teach cast drawing online, and this is the information I give my beginning cast drawing students about casts:
Why Are Casts Expensive? Even though plaster seems like a humble material, casts are valuable because they are rare Casts are made by pouring plaster into molds created from the original sculptures. Molds wear out, they are difficult to acquire, and the process for creating a proper cast requires a high level of skill attained through a lineage of master craftspeople. For this reason we recommend ONLY buying quality casts from these vendors: USA: https://www.capronicollection.com/
I recommend drawing one the “Features of David” casts, if this is your first cast drawing. There are several versions, but I recommend one of these specific features:
I do not recommend alternate versions of the Features. Those are not casts from the original Michelangelo sculpture, they are copies made by a modern sculptor.
Choose Flat White Finish
Flat white is a matte, non-glossy finish. Casts with a glossy finish will be too reflective: You will see shiny specular highlights and too much reflection within the shadows, which leads to perceptual errors when judging values.
Cheap Casts are not a Good Deal
Beware of buying lesser casts for a “deal”. Don’t buy lower-quality versions of the David Features that are casts of copies made by modern sculptors, or low-quality "surmoulage" versions, which means a cast of a cast.
The whole point of drawing a cast is to learn about form from the hand of a master, through an accurate and faithful cast of the original. Most students spend at least 80-200 hours on their first cast drawing. It’s well worth investing ~$65 in the most pivotal exercise of your skill-based art education.
How to Set Up and Light Your Cast
Light your cast with one lamp, and light your easel with bright ambient room light or a second lamp. Make sure the cast lamp is the only light hitting your cast. You may want to construct a 3-sided shadow box by taping together black foam core, to block extra light from hitting your cast.
Control the Lighting The shadows on your cast should be very dark. If you have
more than one light source, or ambient room light hitting your cast, you will not be able to see clear shadow shapes. If you are struggling to block extra light hitting your cast, use “Cinefoil”, which is a matte black tin foil used to control the light on film and photography sets.