> Last weekend on my new hatch I've coated one side with Gluvit epoxy
> resin/sealer. I ran out of one batch when I did the larger upper board so i
> mixed a new batch for the lower. The upper is pretty hard now, but the
lower
> (from the other batch) is still a bit tacky. Maybe i didn't use enough
> hardener? Will it eventually harden given enough time? Is this normal? I
put
> it under a heat lamp last night. I may have gone with a little thicker coat
> on the bottom piece, so that might be a factor.
>
Hi Eric,
Some possible reasons for this --
1. the ambient temperature was too cold for the hardener you used,
2. you didn't mix the hardener in thoroughly,
3. you didn't use the right amount of hardener,
4. the epoxy was contaminated (wax usually),
5. you tried to put a second coat over a fully-cured first coat without
washing off the "amine blush" residue and sanding first.
If it doesn't harden within a day using the heat lamp, you've got a bad batch
of epoxy or the surface you coated was contaminated. I've never used Gluvit,
but I have used West System extensively. A thicker layer cures faster than a
thin layer because the polymerizing reaction gives off heat (exothermic),
which speeds up the cure time. A thick layer gives off more heat. So your
thick layer should have cured faster, all things being equal (like ambient
temperature)
>From your brief description, I'm not sure what went wrong, but maybe you
didn't use enough hardener or mix it well enough. With epxoy resin, you have
to mix the hardener in very, very thoroughly. It doesn't disperse by itself,
like polyester resin.
I use tongue depressors for mixing sticks. I cut off the rounded edge to a
square edge to get in the corners at the bottom of the container (use an
unwaxed paper cup, polyethelene or tin can, please) and I scrape the sides
very carefully while I'm mixiing. I never use the last drop left in the
mixing pot, because it might contain uncatalyzed resin. I throw the pots away
if there's any hardened epoxy stuck to the sides that might interfere with
mixing thoroughly. (With gelcoat, I pour the mixed polyester gelcoat from
the mixing pot into another pot, just to be sure I leave any unmixed stuff
behind, but I've never had to do that with epoxy)
Also, epoxy requires that you get the proportions of the hardener:resin
exact. Not like polyester.. That's why I switched to West System and I use
their measuring pumps right on the can for small batches (under 8 oz). I
haven't had a bad batch since I switched to West System.
One other possibility is that you put a second coat over a first coat that
had fully cured. You can put a second coat on over a partially cured coat as
long as it's in the gel-stage (you can dent it with your fingernail). If the
first coat has cured, you must wash it with *water* (not acetone) to remove
any amine "blush" and sand it for a mechanical bond. Then I wash it again
with water. If there is a cured first coat with an amine blush on the
surface, the second coat won't cure.
To remove the sticky epoxy- Try acetone first. Try heating to soften it and
scraping with a putty knife. Sand. Wash with soap and water to remove the
amine blush. Then start over with a new batch epoxy.
If you want to extend the "pot life" working time, pour your resin into a
shallow container before you start coating. That way it builds up less heat
from the curing reaction and stays workable longer.
Hope this helps you sort out what went wrong.
Best,
Judy B
Judith Blumhorst, DC
HMS18/P19 Fleet Cap'n, Potters Yachters
1985 WWP19 #266 Redwing
(Rigged so a petite woman can solo)
Sailing on SF Bay, CA
(5-35 knot winds, 2-4' chop, 2-6' swells, and currents up to 6 knots)
Visit <A HREF="http://members.aol.com/jblumhorst/HomePage/index.htm">Judy B's
West Wight Potter Pages
</A>
and <A HREF="http://songbird.com/potter_yachter/">The Official Web Site of
the Potter Yachters
</A>