surface prep question

[rpecot]

OK, there's a million threads related to epoxy and I can't seem to find this specific question... I've done the first epoxy coat on my fiberglass cloth. I've got a couple more coats to go to fill the weave (at least, that's what I've read). It will be at least another day before I have time to start on coat #2 (the epoxy has cured). What kind of surface prep can/should I do? I've read that you need to sand between coats, but I've got exposed weave (it's all wetted out, of course):


Some spots are laid on thick so light sanding will be ok, but 95% looks like the picture above. What do I do? :?:

 

[Kayak Jack]

Rule of thumb is if you add epoxy to existing epoxy within 72 hours, just put it on. It will bond chemically, which is best. After 72 hours, lightly sand to get some rough edges (called "tooth" by us perfeshunal boat builder types) for the new stuff to grip to.

 

[Steve]

Don't worry about the exposed web, when you apply hte next coat, you'd never know ya sanded. . .

 

[gbinga]

Go to the West Systems website and search "amine blush".

Under certain conditions, a waxy, water soluble residue can form on the surface of cured epoxy and potentially interfere with bonding of follow up coats.

It doesn't always happen. I haven't had a problem with it. But they say it can happen.

From what I've read, water and a scrub brush, or wet sanding, either one will remove the residue if there is any. I usually take the boat outside and work it over with brush and hose if it goes past 24 hours, just to be safe.

George

 

[Jimmy W]

There is some pretty good info from CLC here: http://www.clcboats.com/shoptips/epoxy_and_fiberglass/fiberglass_weave_epoxy.html

 

[TeddyMadison]

I ran a scraper over mine after the wet out coat and then did scraper and sanding after that. When I started I was applying with a knife (putty style) so if I didnt scrape and sand, any little bumps got really big really fast on subsequent coats.

Now I am rolling on and smoothing with a chip brush so I can just get by with a light sand after each coat.

Oh BTW, I had to put on 5 coats before the weave went away so don't get discouraged if you see weave after the prescribed 3-4.

Teddy

 

[JEM]

I typically try to do a light sanding, then another coat, light sanding, then another coat, etc, etc.

After 3-4 rounds, the surface looks pretty good. Sometimes an additional 2-3 THIN coats is needed for a mirror finish.

 

[oldsparkey]

If it has been less then 72 hours then I just add another coat to the glass. Over 72 hours then it is a light sanding and more epoxy. Remember I use the epoxy from Raka so if you are using someone elses epoxy things could be different.

Chuck.

 

[rpecot]

So I'm thinking I'll do a light-wet-sanding with those foam sanding blocks they sell at Home Depot. Picked up a 220 grit the other day. I'll swing by and get one or two more this afternoon, in addition the usual odds and ends.

Next question... it's supposed to be raining all weekend here. Everything I read about environmental conditions only refers to ambient temperature affecting cure time. What about humidity? The humidity has actually been unseasonably low for this area recently, but that's all over now. Aside from fumes, etc., should I be concerned about applying epoxy in my closed garage?

 

[Steve]

No expert here, but I think I'd wait for the rain to stop at least. . . seems to me ( and I could be wrong) that the humidity factor would be a contributing factor to that amine blush they were talkin about. . . of course, there's more experienced fellas with the epoxy on here than me. . . . .

 

[JEM]

Humidity can mess with you sometimes. Try to pick the "driest" part of the day to apply and let cure.