This is a problem most of use
come up against at least once.
However it is
unlikely to happen a second time.
Richard wrote to
me asking why his epoxy was still soft 3 days later. He
suggested it might be because of one of:
The
immediate guess is that it's been too cold and wet and the poxy just
needed more time to set. Possible, though with two days under its belt,
I'm wary - guess I'll know by sunday.
I
did have to do a second mix so perhaps I cocked up the mixture - I
weigh my poxy rather than use the pumps so the mix is usually accurate
... unless I mess up the maths.
The
third possibility is this one - the mast and spars were made out of
oregon. These were shaped and sanded late last year, and left to sit
until now. Resin had exuded from the timber over that time - the timber
was covered in little balls. It sanded off nicely, but would this have
affected the poxy?
I'm betting number two ... and
guess I'll know by sunday. Anyone else like to make a guess? Especially
about the resin theory.
Richard
Hi
Richard,
It is down to number 2.
For it to cure on some parts but not others ALMOST
certainly indicates either that the poxy either 1/ wasn't
measured properly 2/ wasn't mixed properly.
As far as a problem of manufacture - I have never seen epoxy
not cure
for this reason. People generally swear on a stack of bibles that they
did everything perfectly (me too!!) but when they mix up another
quantity carefully from the same containers the see that it goes off
fine (me too!!!)
And it went off OK on the other bits.
_______________________ The
effects of surface contamination - won't stop epoxy from curing.
The surface that you put it on can effect the surface FINISH
hugely - if there is contamination you can end up with greater or
smaller amounts of fish-eying - where the poxy refuses to wet the
surface evenly so pulls back from some areas and piles up in others -
but it always goes off.
There is a small chance that something else could have
happened but in
thousands of batches used and tens of thousands of batches sold almost
every problem has come from not mixing or measuring carefully - and the
same materials work fine the next time round when more care is used.
___________________________ Too much hardener or too much
resin
The general rule of thumb is if you are down on hardener it is likely
to cure EVENTUALLY - maybe a week, maybe a month maybe in 10 years.
So it is a matter of how long you are prepared to wait before
deciding to strip it all off
If there is too much hardener it is unlikely to ever cure.
There is a few percentage margin in getting the quantities
right but we
always tell people you have to be PRECISE - that way there will not be
problems.
___________________________ Removing
part cured Epoxy
Sharpen up a cabinet scraper old bean and get the sludgy stuff off -
maybe wait till Sunday just to get an idea of what is happening.
Probably worth scrubbing the surface with a brush and acetone, letting
it dry for a bit and poxying again.
___________________________
Number
of coats
BTW I am very unlikely to agree that one coat only is ever warranted.
It is so easy just to put the proper 2 or three on at the same time.
One coat doesn't give you any of the advantages of using
epoxy - it
will be a bit dry in some areas and you will sand through in quite a
few places with the end result that you haven't protected the timber at
all.
You really need the two (or better three) coats to seal the
surface and allow enough meat for sanding.
It is easy anyhow to apply in one process with no extra
sanding
Wait for the first coat to go a reasonably tacky
then roll on the second coat. And so too for the third.
As you complete each coat hold the roller so it cant rotate
and slide
it slowly and gently along the surface to slick it off - popping all
the bubbles and getting rid of the texture left by rolling.
This might all sound rather cold and clinical, but I do feel
for you -
I have been there a few times. And it doesn't feel better that it was
my fault each time!!!