does gel coat need to breathe

[scottc]

I have been coating houseboats with a product from optimum. I had a potential client that was informed that coating the gelcoat would make it crack because it needed to breathe. is there any truth to this?

[Mike Phillips]

I have been coating houseboats with a product from optimum. I had a potential client that was informed that coating the gelcoat would make it crack because it needed to breathe. is there any truth to this?




I've never heard this as it relates to gel-coats that are full cured and dried. When gel-coat is brand new there's probably a recommended waiting time for any outgassing to occur in the same way that there's not a single automotive paint manufacturer that recommends sealing new paint until at least 30 days have passed to let any solvents and other chemicals used in the paint to outgas.

The two boats I've owned were very old, one was from 1967 and the other from 1970, but the time I bought them I'm confident that any outgassing that was going to occur had already occurred.


What makes gel-coat crack can be caused from too thick of gel-coat over a fiberglas overlay. It's the glass woven material that gives the polyester resin strength. If a pigmented layer of polyester resin is applied to thick over the part with the glass weave material it can crack because it doesn't have the glass fibers inside of it to give it strength.

Time and neglect plus exposure to harsh marine environments will also cause gel-coat to crack as it will dry out and oxidize.


I'd say your potential client is confusing what he's heard about car paints with gel-coats but the customer is always right so maybe stick with a wax or sealant for his projects.


:)