I’ve received some more questions about Fiberglass Mold Making Gelcoat and how to end up with a high gloss shiny finish.
Sonic 1 High Gloss
When constructing a mold for duplication of parts, there are several considerations that must be addressed. The main reasons for using tooling gelcoat versus finishing gelcoat have to do with the hardness of the finish and the shine of the finish.
The finished surface of your mold should be abrasion resistant. Polyester gelcoat is used for making tooling masters and molds where good gloss retention of the surface is of paramount importance. A high gloss finish of the molds surface allows for easier release of your parts and thus extends the life of the mold.
As a side note, in addition to the use of tooling gelcoat, the mold should be considerably heavier and stronger than the part which it is being used to produce.
High gloss finishes produced by tooling gelcoats are less porous than the finish of typical finishing gelcoat. The porous nature can cause parts to stick inside the mold causing release issues that range from difficult releases to completely stuck parts.
There is nothing worse for a mold builder than to have built up anticipation of the first production parts result in the destruction of their mold.
This is why it is so important to follow the steps carefully and thoroughly when preparing a mold for part production, especially a new mold. This preparation begins with the use of tooling gelcoat on the mold.
I always suggest the application of al least two thick coats of tooling gelcoat with construction of a mold. This philosophy continues with multiple applications of release wax and PVA.
The idea is to make the surface of the mold as slick and shiny as possible. Surfaces that are slick and shiny have fewer peaks and valleys on a microscopic level. Less peaks and valleys on the surface of the mold will equate to a decreasing chance of the resin or finishing gelcoat used in the construction of your part from biting into the surface of the mold and sticking.
Building successful molds with polyester resins requires knowledge of the dynamics of mold sticking prior to construction of the mold.
More on surface finishes when I finish this next helicopter . . .
Till then, you take care,
Steve
