On Tuesday, May 17, 2016 at 5:19:44 PM UTC-5, dadiOH wrote:

Got a citation?

Polyester resin doesn't pass water. Talc - the primary other - component is
about the least permeable mineral around; plus, it is encapsulated in the
resin.

If you are asking me, you are asking the wrong guy. I was replying to this:

On Tuesday, May 17, 2016 at 11:47:32 AM UTC-5, wrote:
Since polyester filler is not waterproof the wood can rot under the
filler as well.

It was his information. I have read enough on the subject of polyester resins (not the topic at hand, BTW) to not speak without practical, hands on experience.

Robert