Roma Plastilina is an oil-based modelling clay, similar to Plasticine, manufactured by the Spainsdh company, JOVI. Because it is easy to work oil-based clays into fine details, it is commonly used to help create moulds. However, most people would know oil-based clays because of their use in stop-animation -- also known as "claymation" -- films and advertisements. This is because the oil content allows the clay to remain permanently malleable. While the quality of shop-bought oil-based clays is reliable, they are sometimes cost-prohibitive. If you are up for experimentation, you can use a simple recipe to create your very own version of the fine Roma Plastilina clay found in art supply shops.
Put the wax in a deep pot and heat until the temperature on the thermometer reaches 121 degrees C (250 degrees F).
Add the petroleum jelly and baby oil.
Add the powdered clay slowly and reduce the temperature until the thermometer reads 82.2 degrees C (180 degrees F).
Turn heat to low and stir every couple of hours for 6 or more hours.
Remove clay from the heat at 32.2 degrees C (90 degrees F).
Knead clay until smooth and store in an airtight container.
This recipe will yield a batch of clay about the size of a golf ball; simply double the recipe to increase the yield.
Do not try to make this clay in a crock pot.