Tumbling consists of three separate and distinct operations, in its simplest form, with variations depending on special conditions. These are roughing, cleaning and finishing.
For the roughing operation, fill the barrel about a third full with the articles to be polished. (The size of these objects, by the way, is limited by the fact that too heavy or too large objects might break or injure themselves when falling on each other over and over in the barrel). On top of the plastics, pour enough FF pumice to bring the level about half-way up in the barrel. In some cases, particularly when polishing carved work, it is advisable to add shoe-pegs to the batch, in the proportions of one part of pegs to ten parts of pumice. This gives added friction and the points of the pegs dig into the carvings. If you cannot secure shoe-pegs, take all the scrap plastics pieces you have on hand and break them up with a hammer into bits 1/4" or so in size. Start your barrel to rolling and continue until the necessary smoothness is acquired, usually from 18 to 24 hours. This is done in the section at the end opposite the end where the felt-lined section is located. Watch carefully to see that too much material is not taken off at the corners, or that sufficient heat is not developed by friction to harm the material.
Then dump this batch into the screen-tray, and you are ready to clean the pieces. If only a few, this can be done on a wheel, but a quantity can be cleaned in the center section, after sifting out the pumice.
To clean them, pour them in the center section and cover about half full with medium-coarse hardwood sawdust, dampened with water or kerosene. When they are perfectly clean, which will only take a short time, they can be dumped and sifted. They must be completely cleaned, with all traces of pumice removed, as this would not only interfere with the polishing operation, but would work into the felt lining and stay there.
The polishing or finishing operation is done in the felt-lined section, after the pumice has been cleaned off the articles. Various types of finishing compounds are used, some dry, some creamy. Following is a popular formula:
1/2 lb. Carnauba Wax
1 1/2 oz. Keiselguhr
1 lb. Yellow Beeswax
1 pt. Turpentine
All of the above material can be purchased in a paint-store. This mixture is creamed and used to coat the pegs. The Carnauba and Beeswax are melted together and the Keiselguhr stirred in until it is dissolved. The mixture is then poured over the pegs in the barrel, and the barrel started before the wax cools. When the pegs are well coated about a half hour, place them with the work in the felt-covered section of the barrel, and run for 24 to 36 hours, until the desired polish is obtained.
Pegs and compounds can be used over and over again, using care to keep the various grades separated in order to keep the pumice from getting into the polishing compartment. A final touch on a clean wheel to remove this wax is frequently given for an extra high polish on special work.