The process used in polishing and finishing cast resins varies with the type of job, the quantity, and the materials and equipment on hand. This varies from hand-finishing on the one extreme to the tumbling-barrel on the other.

Tool-Marks

As in polishing and finishing any other material, the entire process consists of a series of steps, each of which removes the coarser marks left by the previous operation, and an ounce of proper care in any one step will save a pound of elbow-grease in the next step.

Beginning at the beginning, then, the first step in finishing may be considered the final cutting and shaping operation and the removal of rough tool-marks. After giving due consideration to speed, the best tool to use is the one that leaves the finest or least tool-marks. This applies to circular - , band - and jig-saw blades, grinding-wheels, lathe-tools, etc. The less coarse your tool-marks, the less work you will have to do in removing them. Every last one must be removed completely, because the brilliant finish possible on plastics shows up the tool-marks like a wave in an old-fashioned mirror, catching and scattering the light. The final cut in a lathe should be made with a tool or chisel having a slightly rounded face presented to the work, and if there has been any "burning", which reduces the surface to a sort of granular, rough texture, this should be removed with the tool, rather than leaving it to sandpaper away, which will take several times as long.

Marks left by a carving tool, likewise, can be smoothed out with the same tool or one with a more rounded contour, in a fraction of the time it would require to remove these humps and scratches with sandpaper. Too much emphasis cannot be placed on doing each portion of the finishing job well as you go along, as you will quickly learn after your first two or three jobs.

A file is often useful for the final touches before taking up the sandpaper.

Bringing out the beautiful and brilliant finish of cast resins is an extremely simple job and I might add a thrilling experience, if it is done right, but it can be tedious drudgery if the earlier steps are slighted or the wrong equipment used.