There's two different problems that might be present, pin holes vs.
cratering.

Pin holes in an epoxy coating are caused by air bubbling out of the wood.
As the epoxy cures, it gets warm, the air expands, and out it comes. The
trick is to prewarm the surface, either with the hot sun or with a hot air
gun. (I use a Black and Decker paint stripper type.) That way the surface
is cooling and the epoxy is drawn into the hole.

Cratering is tougher. It's a failure to bond. Surface tension pulls the
epoxy back away from the spot. I've seen suggestions that one should scrub
the epoxy into the surface with the heel of the roller or maybe "wet sand"
the liquid epoxy into the surface. (Messy!)

Roger

http://home.earthlink.net/~derbyrm

"1088" wrote in message
...
Still fixing my fixer-upper. I chiseled and sanded the crazing in the
gelcoat, then filled with several different things and the cracks are
covered ok but the tiny, tiny pin-holes will not fill. Many of these
looked like tiny black spots at first. Any attempt to fill them
results in some kind of gassing and the filler just ozzes back out
after a while.

On Wed, 15 Jun 2005 06:51:14 +0000, 1088 wrote:

Still fixing my fixer-upper. I chiseled and sanded the crazing in the
gelcoat, then filled with several different things and the cracks are
covered ok but the tiny, tiny pin-holes will not fill. Many of these
looked like tiny black spots at first. Any attempt to fill them
results in some kind of gassing and the filler just ozzes back out
after a while.
Things I've tried:
marine tex
west system epoxy and 407/404/talc
automotive bondo ($13 per gallon)
white yuppie-yacht bondo
system3 epoxy and 404
real smelly blue spot putty from the auto store
I was reasonably pleased until I sanded the second coat of primer
(parker 1040) vacuumed and washed and, and, and there they are again-
sons of bitches!
I'm definately open to suggestion at this point. Thanks for your time
as always.

You put bondo on a boat? I've heard that it has gypsum or something in it
and is a disaster on boats. I don't have any firsthand experience.
Hopefully it is not true and someone can confirm.

Roughly how many spots are there? And how wide are they?

What I'm getting at is would it be feasibly to treat them individually
with some kind of rotary tool?

--Mac

On Wed, 15 Jun 2005 06:51:14 GMT, 1088 wrote:

Still fixing my fixer-upper. I chiseled and sanded the crazing in the
gelcoat, then filled with several different things and the cracks are
covered ok but the tiny, tiny pin-holes will not fill. Many of these
looked like tiny black spots at first. Any attempt to fill them
results in some kind of gassing and the filler just ozzes back out
after a while.
Things I've tried:
marine tex
west system epoxy and 407/404/talc
automotive bondo ($13 per gallon)
white yuppie-yacht bondo
system3 epoxy and 404
real smelly blue spot putty from the auto store
I was reasonably pleased until I sanded the second coat of primer
(parker 1040) vacuumed and washed and, and, and there they are again-
sons of bitches!
I'm definately open to suggestion at this point. Thanks for your time
as always.

Maybe what you call "white yuppie-yacht bondo" should have been used
throughout. Automotive bondo _will_ absorb moisture. It may be
released when overcoated. Pinholes are the result.

I have no idea if this is what happened, but it certainly is likely.

Your "white yuppie-yacht bondo" costs about 8-9 bucks a quart. The
auto bondo cost maybe 5-6 a quart. Was it worth it to save three
dollars a quart? Didn't think so.

The most expensive ingridient in boatbuilding is labor. It's folly to
skimp on materials.

You need to use 3m spot puddy. It will fill the pinhole and be dry in 20
min. Then sand with 220 and paint.
http://products3.3m.com/catalog/us/e...er/output_html
--
Shield Finishes and Nauticoat Marine Finish Systems
www.shieldfinishes.com
"P.C. Ford" wrote in message
...
On Wed, 15 Jun 2005 06:51:14 GMT, 1088 wrote:

Still fixing my fixer-upper. I chiseled and sanded the crazing in the
gelcoat, then filled with several different things and the cracks are
covered ok but the tiny, tiny pin-holes will not fill. Many of these
looked like tiny black spots at first. Any attempt to fill them
results in some kind of gassing and the filler just ozzes back out
after a while.
Things I've tried:
marine tex
west system epoxy and 407/404/talc
automotive bondo ($13 per gallon)
white yuppie-yacht bondo
system3 epoxy and 404
real smelly blue spot putty from the auto store
I was reasonably pleased until I sanded the second coat of primer
(parker 1040) vacuumed and washed and, and, and there they are again-
sons of bitches!
I'm definately open to suggestion at this point. Thanks for your time
as always.

Maybe what you call "white yuppie-yacht bondo" should have been used
throughout. Automotive bondo _will_ absorb moisture. It may be
released when overcoated. Pinholes are the result.

I have no idea if this is what happened, but it certainly is likely.

Your "white yuppie-yacht bondo" costs about 8-9 bucks a quart. The
auto bondo cost maybe 5-6 a quart. Was it worth it to save three
dollars a quart? Didn't think so.

The most expensive ingridient in boatbuilding is labor. It's folly to
skimp on materials.

On Sat, 18 Jun 2005 06:27:50 -0400, "Bruce on horizon"
wrote:

You need to use 3m spot puddy. It will fill the pinhole and be dry in 20
min. Then sand with 220 and paint.
http://products3.3m.com/catalog/us/e...er/output_html

If the pinholes are due to moisture entrapment as a result of using
cheapy materials, the pinholes will keep coming until all moisture has
been liberated.