Is it necessary to use polyvinyl alcohol (PVA) in addition to wax?
The answer to this question depends on a number of factors but the bottom line is this: if you do not want a part to stick to and possibly ruin your mold, then use PVA over a wax mold release. If the mold is new or reconditioned, then you should definitely use a PVA such as Partall® Coverall Film or Partall® Film #10 to prevent styrene migration. If the mold is seasoned, then use of PVA is not absolutely necessary except as additional insurance against sticking as long as wax is applied properly and with sufficient frequency. If the mold is very large or intricate you may have difficulty achieving adequate coverage using wax only. PVA can be sprayed into hard-to-reach crevices and forms a visible barrier you can see on the mold surface. For additional information on the benefits of using PVA (particularly on new molds), please read “Why Molds Stick” by Bob Lacovara (Fabrication News, Feb 1991).
