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

Jay,
Let me just point out something . . .

Because I want to do something - NOT 'boatbuilding critical' - with a small
MASS of epoxy, I contacted the 'repackager' I use{Larry at RAKA Epoxy}. He
confirmed, & refined, my thinking. Due to the chemistry involved, as little
as 5 PERCENT 'hardener' will cause properly mixed epoxy to cure. That 'cure
time' will simply increase {probably geometrically or exponentially}.
Bearing in mind that the stuff is 'time & temperature dependent' - in this
instance lets agree to an approx 70 degree constant.

The other point is that the 'higher' the ratio { I favor the 5 to 1,
resin-to-hardener, formulation for most of my use}the HARDER {and more
brittle} the cure. Everything being relative, if you are NOT making a
'block' of the stuff, it shouldn't make any difference in 'our' type of
projects. What 'additives' & 'fillers' we use has more of an effect. Talc
vs. 'Agricultural Limestone', for instance.

What Larry and I were discussing was using a 2 to 1 'formula' at 3 to 1. The
idea being to slow down the exothermic reaction. It would do exactly that,
the cure time would lengthen very much, and the finished 'slug' would be
'less brittle, and a bit less hard' - EXACTLY what I wanted !! {In a
'boatbuilding scenarios that would equate to 'more flexible' - again a 'good
thing'.}

Regards & Good Luck,
Ron Magen
Backyard Boatshop

"Jay Chan" wrote in message
ups.com...
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

You are saying that a bit less hardener (3-to-1 instead of 2-to-1) will
result with the cured epoxy to be a bit more flexible, and this may not
be a bad thing depending on the intended use of the final product.
This is interesting and is good to know.

In my case, the ratio was actually 4-to-1 instead of the suggested
2-to-1 ratio because I likely only added half of the recommended
hardener. This was much less hardener than 3-to-1. Moreover, I am
under the impression that the MAS brand of epoxy tends to cure to a bit
more flexible than other brand of epoxies (I seem to come across of
this info somewhere in this newsgroup). This means the final product
is even more flexible than what 4-to-1 ratio would have suggested --
may be like what 5-to-1 ratio would have been (that is just a wild
guess). And then compounded with the possibility that I might not have
spent the recommended two minutes to mix the stuff... This means I
really have two negative factors against me -- not enough hardener, and
not enough mixing. And I should question the quality of the final
product that I had made. In other words, I should undo the "repair"
that I have made.

Jay Chan


Ron Magen wrote:
Jay,
Let me just point out something . . .

Because I want to do something - NOT 'boatbuilding critical' - with a small
MASS of epoxy, I contacted the 'repackager' I use{Larry at RAKA Epoxy}. He
confirmed, & refined, my thinking. Due to the chemistry involved, as little
as 5 PERCENT 'hardener' will cause properly mixed epoxy to cure. That 'cure
time' will simply increase {probably geometrically or exponentially}.
Bearing in mind that the stuff is 'time & temperature dependent' - in this
instance lets agree to an approx 70 degree constant.

The other point is that the 'higher' the ratio { I favor the 5 to 1,
resin-to-hardener, formulation for most of my use}the HARDER {and more
brittle} the cure. Everything being relative, if you are NOT making a
'block' of the stuff, it shouldn't make any difference in 'our' type of
projects. What 'additives' & 'fillers' we use has more of an effect. Talc
vs. 'Agricultural Limestone', for instance.

What Larry and I were discussing was using a 2 to 1 'formula' at 3 to 1. The
idea being to slow down the exothermic reaction. It would do exactly that,
the cure time would lengthen very much, and the finished 'slug' would be
'less brittle, and a bit less hard' - EXACTLY what I wanted !! {In a
'boatbuilding scenarios that would equate to 'more flexible' - again a 'good
thing'.}

Regards & Good Luck,
Ron Magen
Backyard Boatshop

"Jay Chan" wrote in message
ups.com...
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

Jay Chan wrote:

You are saying that a bit less hardener (3-to-1 instead of 2-to-1) will
result with the cured epoxy to be a bit more flexible, and this may not
be a bad thing depending on the intended use of the final product.
This is interesting and is good to know.


Well epoxy works by the two different types of molicules each having two
reactive sites, one on each end. Its a chain polymerisation reaction.
When it gets to run to completion, it form *LONG* chains and sets pretty
hard. If there is an excess of one component, you get un-paired
reactive sites left over. This limits the chances of a long chain
forming and so you get a lot of short chains and a jelly like result.
Its more damaging than just the dilution the same amount of an in-active
resin would cause. I suppose that for a non-critical glueing
application like sticking down non-skid, a certain rubberyness *may* be
desirable, but I've always found that bad mixes are unacceptably weak
*and* I wouldn't want to risk the long term health consequences of being
around inproperly cured epoxy.

Get out your scraper and a hot air gun and get it all cleaned off. If
its as badly off ratio and as poorly mixed as you say, 99% of it will
come off pretty easily. You wont be happy unless you've got rid of it
and fixed it right.

N.B. treat the stuff you scrape off as toxic and wear gloves &
appropriate protective clothing. You'll be much happier *without* an
epoxy allergy for the rest of your life (and you'll save a lot of money
as *IF* you get an epoxy allergy, you wont be able to work with the
stuff again so will be paying a yard through the nose to do repair work)


--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & 32K emails -- NUL:
'Stingo' Albacore #1554 - 15' Early 60's, Uffa Fox designed,
All varnished hot moulded wooden racing dinghy.

Ian Malcolm wrote:
Jay Chan wrote:

You are saying that a bit less hardener (3-to-1 instead of 2-to-1) will
result with the cured epoxy to be a bit more flexible, and this may not
be a bad thing depending on the intended use of the final product.
This is interesting and is good to know.


Well epoxy works by the two different types of molicules each having two
reactive sites, one on each end. Its a chain polymerisation reaction.
When it gets to run to completion, it form *LONG* chains and sets pretty
hard. If there is an excess of one component, you get un-paired
reactive sites left over. This limits the chances of a long chain
forming and so you get a lot of short chains and a jelly like result.
Its more damaging than just the dilution the same amount of an in-active
resin would cause. I suppose that for a non-critical glueing
application like sticking down non-skid, a certain rubberyness *may* be
desirable, but I've always found that bad mixes are unacceptably weak
*and* I wouldn't want to risk the long term health consequences of being
around inproperly cured epoxy.

Thanks for the explanation why improperly cured epoxy is not good. I
will make sure I add the proper amount of hardener and spend enough
time to mix it.

Get out your scraper and a hot air gun and get it all cleaned off. If
its as badly off ratio and as poorly mixed as you say, 99% of it will
come off pretty easily. You wont be happy unless you've got rid of it
and fixed it right.

I am thinking of getting out a circular saw and cut the whole deck out
(as mentioned in another of my post).

N.B. treat the stuff you scrape off as toxic and wear gloves &
appropriate protective clothing. You'll be much happier *without* an
epoxy allergy for the rest of your life (and you'll save a lot of money
as *IF* you get an epoxy allergy, you wont be able to work with the
stuff again so will be paying a yard through the nose to do repair work)

I believe you are referring to uncured epoxy as being toxic like. I
will make sure I have proper protection when I start working on the
boat in the coming spring.

Thanks for the info.

Jay Chan

Jay,
Ian said, '. . . treat the un-cured epoxy {that you are scraping} AS toxic .
.. .' - NOT that it IS 'toxic'. It is simply not the nicest stuff in the
world, and I think he means you should protect your eyes, skin, & lungs. The
same 'coverage' you would use when installing / removing fiberglass
insulation. Disposal is the same - DON'T just throw it in the can, carefully
bag it, first. The bit about rubber gloves & skin is directly related to
ALLERGIC reactions. Some people get an instant 'reaction' to things {like
'Poison Ivy'}, some never do, and others develop it at a later time in life.
With epoxy, once it does appear - it supposedly never leaves.

With the 'ratios' you got it reversed - the 'higher' ratios {like my 5-to-1}
tend toward the 'harder & brittle'. the 'lower' ratios tend toward the 'less
hard & more flexible'. ALSO NOTE - I said 'everything is relative' and my
particular project was NOT 'boatbuilding critical'. It has NOTHING to do
with boatbuilding. I consider ALL boatbuilding uses to BE 'CRITICAL'.

ALWAYS - Practice, Test, & Take & Keep Notes.

Regards & Good Luck,
Ron Magen
Backyard Boatshop

"Jay Chan" wrote in message
ups.com...
Ian Malcolm wrote:
Jay Chan wrote:

You are saying that a bit less hardener (3-to-1 instead of 2-to-1)
will
result with the cured epoxy to be a bit more flexible, . . .
SNIP
N.B. treat the stuff you scrape off as toxic and wear gloves &
appropriate protective clothing. You'll be much happier *without* an
epoxy allergy for the rest of your life . . .

Ron Magen wrote:

Jay,
Let me just point out something . . .

Because I want to do something - NOT 'boatbuilding critical' - with a small
MASS of epoxy, I contacted the 'repackager' I use{Larry at RAKA Epoxy}. He
confirmed, & refined, my thinking. Due to the chemistry involved, as little
as 5 PERCENT 'hardener' will cause properly mixed epoxy to cure. That 'cure
time' will simply increase {probably geometrically or exponentially}.
Bearing in mind that the stuff is 'time & temperature dependent' - in this
instance lets agree to an approx 70 degree constant.

The other point is that the 'higher' the ratio { I favor the 5 to 1,
resin-to-hardener, formulation for most of my use}the HARDER {and more
brittle} the cure. Everything being relative, if you are NOT making a
'block' of the stuff, it shouldn't make any difference in 'our' type of
projects. What 'additives' & 'fillers' we use has more of an effect. Talc
vs. 'Agricultural Limestone', for instance.

What Larry and I were discussing was using a 2 to 1 'formula' at 3 to 1. The
idea being to slow down the exothermic reaction. It would do exactly that,
the cure time would lengthen very much, and the finished 'slug' would be
'less brittle, and a bit less hard' - EXACTLY what I wanted !! {In a
'boatbuilding scenarios that would equate to 'more flexible' - again a 'good
thing'.}

Regards & Good Luck,
Ron Magen
Backyard Boatshop



------------------------------------------

NO NO NO! ALL WRONG!

With epoxy resins the mix ratio is exactly the amount of part a needed
to react with part b. Shift that ratio and you have excess part a or
part b remaining. Note that one can usually be off about 15-20% and
things will still cure up OK. With polyester resins the part b is a
catalyst not a reactant so you can adjust the part b to control the
reaction. Some epoxies blush more than others, that should a real
concern to everyone - especially if they use excess part B.

The mix ratio tells you nothing about the properties of the epoxy - it
just is the way the chemistry worked out between the resin and the
curing agent(s) used.

Some epoxies are more brittle than others. Flexing agents can be added,
also.

Unless the vendor is a simple repackager - the vendor/formulator can
'create' the epoxy properties they want (hardness, brittleness, potlife
etc. - I'm currently working on a very thin epoxy with long potlife for
vacuum bagging). The 'creation' process also affects epoxy paints more
than the 'marine resins' which are typically just less complex recipes.

Some epoxies also offer slow (warm weather) curing agents but you can
control pot life and cure by temperature and mass. The chemical
reaction, like all chemical reactions, doubles or halves with every 18
degree F change in temp. The amount of product mixed and the shape of
the container also control the 'heat' and potlife (like critical mass in
a nuclear reaction).


I find it interesting that none of the other epoxy vendors/formulators
bother to monitor/lurk/respond to any of the boating newsgroups.


paul oman
progressive epoxy polymers, inc.
www.epoxyproducts.com/marine.html

"Jay Chan" wrote in message
oups.com...


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

Ron Magen wrote:
Jay,
Ian said, '. . . treat the un-cured epoxy {that you are scraping} AS toxic .
. .' - NOT that it IS 'toxic'. It is simply not the nicest stuff in the
world, and I think he means you should protect your eyes, skin, & lungs. The
same 'coverage' you would use when installing / removing fiberglass
insulation. Disposal is the same - DON'T just throw it in the can, carefully
bag it, first. The bit about rubber gloves & skin is directly related to
ALLERGIC reactions. Some people get an instant 'reaction' to things {like
'Poison Ivy'}, some never do, and others develop it at a later time in life.
With epoxy, once it does appear - it supposedly never leaves.

Yes, I understand that it is not truely toxic. That's why I said it is
"toxic like". And I pretty much follow what you have suggested to
protect myself. This is good to be reminded for such an important
thing.

With the 'ratios' you got it reversed - the 'higher' ratios {like my 5-to-1}
tend toward the 'harder & brittle'. the 'lower' ratios tend toward the 'less
hard & more flexible'. ALSO NOTE - I said 'everything is relative' and my
particular project was NOT 'boatbuilding critical'. It has NOTHING to do
with boatbuilding. I consider ALL boatbuilding uses to BE 'CRITICAL'.

I don't quite understand. If you put less hardener into the mix, I
would assume that the final result will be less hardened and more
flexible, right? Do you mean to say that the mixture that has less
hardener than it should will not be properly cured and will not provide
the proper suggest?

This is probably not an issue because I will not play around with
varying hardener ratio anyway. I need to strictly follow the
manufacturer's recommendation of the hardener ratio.

Jay Chan