Gelcoat question(s)

[KJM]

I was talking to my fiberglass suppler today about gelcoat and mentioned getting unwaxed gelcoat because i'll probably need a second coat. He said if you apply the second coat within 48 hours of the first coat it doesn't matter about the wax because it won't have come to the surface yet and will just carry on to new top surface. He said unless its real hot out or under heat lamps it will be fine. He also suggested that even after 48 hrs, the surface wax would likely still migrate thru the new coat. Anyone ever hear of that before? On a side note, how does the wax "know" which way to go to get to the surface? On the bottom of the boat it has to go down, on the top it has to go up and on the sides it needs to go left or right!

 

[Meames1]

I can't help you with the subsequent coats question, although I too would like to know. I got unwaxed and did several coats and added wax in the top coat only as I was worried about adhesion to the earlier coats.
As far as you second question, the wax goes to the surface as it doesn't "mix" chemically. Think Like oil coming to the surface of water, the gelcoat is heavier therefore the wax will always go to the top or outside on vertical etc.

 

[Scott Danforth]

you may want a second opinion on that.
also, depending on how you are applying gel, you may not want wax.

 

[Emerger]

I was talking to my fiberglass suppler today about gelcoat and mentioned getting unwaxed gelcoat because i'll probably need a second coat. He said if you apply the second coat within 48 hours of the first coat it doesn't matter about the wax because it won't have come to the surface yet and will just carry on to new top surface. He said unless its real hot out or under heat lamps it will be fine. He also suggested that even after 48 hrs, the surface wax would likely still migrate thru the new coat. Anyone ever hear of that before? On a side note, how does the wax "know" which way to go to get to the surface? On the bottom of the boat it has to go down, on the top it has to go up and on the sides it needs to go left or right!

Your supplier is right but I wouldn't follow his advice. That makes sense, right?

Wax does take some amount of time to form on the surface of the gelcoat but it's too difficult to guess at precisely how long it takes and far too easy to simply mix wax surfacing agent into the final coat without having to worry about it. You can experiment with some if you'd like and see for yourself how long it takes. It's easier to see the finished wax on the surface using plain polyester resin instead of gelcoat. Drop a thick puddle of waxed resin on something and see how long it takes to form a whitish haze on top. The wax doesn't actually float up but is excreted during the polymerization process. It is dissolved in liquid resin but does not become part of the cured product.

 

[KJM]

Your supplier is right but I wouldn't follow his advice. That makes sense, right?

Wax does take some amount of time to form on the surface of the gelcoat but it's too difficult to guess at precisely how long it takes and far too easy to simply mix wax surfacing agent into the final coat without having to worry about it. You can experiment with some if you'd like and see for yourself how long it takes. It's easier to see the finished wax on the surface using plain polyester resin instead of gelcoat. Drop a thick puddle of waxed resin on something and see how long it takes to form a whitish haze on top. The wax doesn't actually float up but is excreted during the polymerization process. It is dissolved in liquid resin but does not become part of the cured product.

Thanks, that actually makes sense! I guess as the deeper resin cures it pushes the wax towards less cured resin which will be the surface, whatever the direction it is, because of contact with oxygen?

 

[Scott Danforth]

depending on your temp and your mix, your talking it could be fully cured in a few hours

again, how are you applying the gel. duratech 904 additive is great for spraying and rolling and you dont need wax

The only time I use wax is rolling interior cabin bins and floor prior to finishing with EVA foam or other

 

[KJM]

depending on your temp and your mix, your talking it could be fully cured in a few hours

again, how are you applying the gel. duratech 904 additive is great for spraying and rolling and you dont need wax

The only time I use wax is rolling interior cabin bins and floor prior to finishing with EVA foam or other

Yeah, I was planning on rolling it on and figured I would need 2 coats as I'm changing the color and will need to sand out the orange peel effect. I'm also still considering using paint, but gelcoat seems more durable.