I have decided to totally remove the epoxy that had taken many weeks to
cure.

I thought the reason why the epoxy took so long to cure had to do not
spending enough time to mix it with hardener. Then I caught myself
adding only half of the required hardener into the mixture when I was
working on a different area of the deck. The manufacturer's 2-to-1
ratio is only applicable if I measure the ingredients by volume. When
I am using the pump, I should stick to the "one-pump-each" ratio. I
might have pumped two times for the resin, and pumped one time for the
hardener; and this resulted with very slow curing.

I have done some limited tests on various hardeners and various way of
mixing them. And I come to this conclusion regarding the use of MAS
brand of epoxy and hardener:

1. Spent half of the required mixing time will result with slightly
slower
curing time than normal if I use _slow_ hardener. But the
difference
is small.

2. Spent half of the required mixing time will not increase the curing
time if I use _medium_ hardener.

3. Added half of the required hardener will result with very long
curing
time if I use _slow_ hardener. And the "cured" epoxy is not
strong.

4. Added half of the required hardener will result with long curing
time
if I use _medium_ hardener. And the "cured" epoxy doesn't
seem to be strong (not sure).

My observations from the test result a

o Because I used slow hardener when I was preparing the area of the
deck that cured very slowly, I am sure that I must have added too
little hardener (that matches the test case # 3 above). This
means
all the works that I have done on the deck so far is questionable.
I should remove them and start over.

o Manufacturer's suggested mixing time must have added enough
margin of error in case people doesn't spend enough time mixing.
That doesn't mean I should cut back on mixing time though.

o MAS brand of slow hardener seems to be less forgiving than
their medium hardener. I think I should stick to medium
hardener from now on as much as possible.

Jim Conlin said:
Unless you have done some tensile tests on your epoxy, and
have found that its strength equals the manufacturer's published
figures, your statement that it has cured "completely" is
unfounded. Further, it is the height of irresponsibility to suggest
that others listening here might rely on the approach you've taken.
In my view, you've rolled the dice and whether your boat holds
together remains to be seen. Please don't suggest that others
take the same risk. Lives could be at stake.

Thanks for pointing this out. That got me thinking along that
direction, and found out what went wrong.

Jay Chan