Getting to the bottom of it... (Ablative question)
 

On 24 Aug 2006 21:24:02 -0500, Dave wrote:

Epoxies must be sealed off
from air exposure in order to cure.

That is not true, you are thinking of polyester resin, not epoxy.

They are not the same.

Getting to the bottom of it... (Ablative question)
 

Exactly right Wayne!

Some Polyester and Gelcoat sold for car and boat repairs in hardware stores
contains wax, but commercial gelcoat used in moulds and polyester resin used
for laminating does not. For a proper cure, polyester must be shielded from
the air and the wax floats to the surface and inhibits reactions with the
air. Applying wax paper or plastic film over small repairs allows wax free
gelcoat/resin to cure hard.

Epoxy resins do NOT contain wax and do not need it! But, poor quality
epoxies do "blush" - this is a wax-like material that forms on the surface -
It is not wax, but is formed by a reaction between amines in the hardener
and water and carbon dioxide in the air to form an amine carbonate. This is
not a problem when laminating, but if the epoxy is allowed to fully cure,
this product must be scrubbed or sanded off before applying more epoxy or
paint.


"Wayne.B" wrote in message
...
On 24 Aug 2006 21:24:02 -0500, Dave wrote:

Epoxies must be sealed off
from air exposure in order to cure.

That is not true, you are thinking of polyester resin, not epoxy.

They are not the same.

Getting to the bottom of it... (Ablative question)
 

Which of the two types is West 105?

Can one just varnish over a non-waxed
epoxy to allow it to cure?

Thanks,

Chris

Dave wrote:
On Thu, 24 Aug 2006 22:04:54 -0400, DSK said:

I wonder if the problem was amine blush. This is a waxy film
that develops across the surface of most epoxies as they cure.

Actually, it isn't something that just happens. Epoxies must be sealed off
from air exposure in order to cure. That's what the wax does. You can also
buy epoxies that don't have the wax, and don't have it specifically so that
additional layers can be added before the final cure. To cure these you have
to either spray with wax coat, or cover the surface of the epoxy with an
airtight wrap.

Getting to the bottom of it... (Ablative question)
 

On 24 Aug 2006 22:14:11 -0700, wrote:

Which of the two types is West 105?

All of the West System resins are epoxy and will cure with or without
air.


Can one just varnish over a non-waxed
epoxy to allow it to cure?

See above. There is no such thing as non-waxed epoxy, that is
polyester resin, different animal. Before you varnish or paint epoxy
it should be totally cured, cleaned, and lightly sanded.