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Epoxy resin problems

I am working with Devcon 2-ton epoxy resin with a 30min working
time. I have begun to use it in large quantities… mixing about
half the bottle at a time and pouring it from a disposable wax lined
paper coffee cup. Previously I had been using wax paper to mix small
quanitites to fill bezel cups. Today is the first time over the last
6 months or so that I have been working with this stuff that I
encountered the resin heating to extremely hot temps, smoking or
steaming (I am not sure which) and solidifying within about 10
minutes. It had a really nice pouring consistency for the first few
minutes then it started getting so hot I could not hold the cup, I
went back to stir it a little it was allready hardening in the
middle and was as hard as it usually becomes when left over night in
a matter of a few minutes. HELP! am I doing something wrong? Is it
something with the wax cups?

Thanks for any help and or experience you can offer!

Rebekah

Hi Rebekah!

How long have you been working with the large quantities? I would
imagine that the increased catalyst with the epoxy is working
overtime and trying to harden. More is not necessarily better. At
most, I would mix not more than two tablespoons each at a time.

You can actually control the curing times with slightly varying the
quantities of hardner. A little more and you will get a faster cure,
a little less, a little longer. The variations should be in small
increments.

Using the wax paper is a good idea, as you can see through the paper.
Mark circles on the opposite side, by increasing the size. Dispense
your expoxy according to the sizes on the circle. A little more
hardner, a little less harder and document your cure times. This is
a good way to decrease your labor, because you will know exactly how
much epoxy to work with.

Good luck!
-k

Dear Rebekah,

It could be a number of reason for your problem and Im not sure
about the exact brand of resin you are using, but for larger
quantities you must have casting resin. Any other kind will heat up
way too much. It will cause the work to shatter after cooling down
and also can go yellow.

If the resin is ok for casting, than maybe you should try to reduce
the amount of catalyst that you are using.

Years ago I used to cast black opal chips into resin and without any
training, I just learned by my mistakes as I went along. Plenty of
mistakes too.

I hope this helps.
Have fun with resin.

Epoxy resins cure by reaction of the resin with a curing agent. The
mix ratios are rather critical and will depend on the formulas you
have. Too much of either component does not help.

Polyester resins are different in that the component added is a
true catalyst which promotes the reaction but does not take part in
it otherwise. Too little catalyst will still make the reaction go
but it will be slower. Too much and the reaction goes too fast and
heats up damaging the result or even causing a fire. This is the
type resin used in simple fiberglassing ( epoxy some time used there
also). Casting resins are also commonly polyester-- not always.

Heat makes curing go faster with both systems. Polyester resins
will eventually get hard by themselves without any added
catalyst.-- epoxies won’t cure by themselves.

Unless you are a polymer chemist follow the instructions.

jesse

Be careful adjusting the epoxy ratios, you will end up with sticky
surfaces that don’t ever harden.

James McMurray
@James_McMurray

You mentioned that you were using Deco epoxy resin, they have a
website http://www.deco-coat.com/ They have a mixing gun and the resin
comes in tubes and the it has a mixing tube on the front. So there is
no need to mix and measure and… Just push the exact amount of resin
out that you need one piece at a time.

Rebekah, I have an idea you were using cups that were actually
plastic-coated, not wax. I once, long ago, got the same reaction
putting the epoxy on a small scrap of Ultrasuade “fabric.” Smoked
and self-destructed. Nothing in instructions said please do not glue
Ultrasuede. So, stick to genuine waxed paper products if you can
find them.

Good luck.
Pat

Hi Folks…

I’ve used the Devcon 2 Ton Epoxy for a number of years…for
mounting tools, jewelry, and affixing all sorts of things…

I’ve always used the two barrel syringe (25ml)…it lets you get
your 1 to 1 ratio pretty accurately… You can lay out what you need,
mix (I use wax paper) and cap the syringe for later…

I always make sure I mix it for a full minute…

The mixing nozzles are great for large volume applications, but
since they’re mixing the stuff up inside, when you’re done…I
would think it would set up inside of the nozzle… This would mean
you need a new nozzle the next time you want to use the stuff…

I know the nozzles are big business for 3M and Loctite…maybe
Devcon too……

Gary W. Bourbonais
A.J.P. (GIA)

Hi Rebekah,

I’m surprised that you didn’t call me first before posting this -
you know I’ve worked with resin three dimensionally as well as the
inlay. Anyhow, the gal who mentions here that layering might work
is right on - try it by letting the first layer cure and then
pouring more on top the next day - that should work but you will
have to scribe and rough up the resin between each layer and make
sure your resin/hardener ratios are perfect. If you have begun to
work THIS big, I would recommend contacting someone who carries
casting resin that will work for your larger jobs. Hope you are
well, and I look forward to seeing what you’ve been making.

Lulu Smith

Dear Rebekah and others,

I have experienced the same phenomenon with epoxy.

Anyway, here’s the way I understand it and have solved my problems.

My previous experience was using very small quantities as adhesive.
By “small” I mean generally mixing a tablespoon or less at a time.
Later I had occasion to mix larger quantities - by which I mean a
cup or more at a time. Then I noticed the heat problem. It is easy
to solve. Here’s how it happens and how to solve it.

The chemical reaction by which the epoxy hardens produces heat. In
small applications, say mixing a wee bit on a flat surface or even
in a small container, the surface area of the mixture is relatively
large and so the heat dissipates quickly to the surrounding
environment. When you mix “large” quantities most of the mixture
is not close to the surface where it can dissipate the heat
generated by the chemical reaction. Also, because the stuff is
thick and sticky, it doesn’t circulate within its container by
convection the way water would if heated. So the heat at the
center of the mass stays where it is. Finally, heat accelerates
chemical reactions, therefore the reaction proceeds ever faster as
the temperature rises thus producing more heat faster and thus
reacting faster and thus … well I think you get the idea. Heat
will also accelerate the hardening of the mixture so your working
time is drastically reduced or even eliminated altogether.

The solution is to mix your epoxy so that it has a chance to
dissipate the heat. That might mean that instead of mixing in a deep
container, (tin can or plastic yogourt container), you might use a
pan which is wide and shallow, like a disposable aluminum pie plate
, tray, or cookie sheet or some similar container. The stuff
spreads out into a thinner layer, more surface is exposed to the
air, and heat can escape. Also the material of the container
should be conductive so that heat can easily pass out through the
walls and bottom of the container. So a metal container would be
better than plastic or glass. You can use a wide spatula-like
stirrer instead of a small stick.

One of the other people suggested varying the hardener-resin ratio.
I’m not enough of a chemist to know about that. However, in
researching the topic earlier I have learned that there are many
different kinds of “epoxy” produced for the various intended
purposes. Some of them require quite specific conditions to work as
intended; temperature, humidity, proportions of mixture etc.
Without being quite certain of the properties of the epoxy at hand,
I wouldn’t mess with the proportions. It might work, or not at all.
You can check with the manufacturer for technical info.

But the heat problem can be solved as described above. Keep it cool
and mix in a way that allows heat to escape.

ALSO - Definitely do not mix in waxed cups as the heat will melt
the wax into the epoxy and wax causes no end of trouble in all sorts
of ways.

ALSO - Epoxy frequently produces allergic reactions, sometimes
quite serious and dangerous. I have known people who have become
sensitized to the stuff over time so that years later they could not
walk into a room where it was being used without swelling up as
though snake-bitten. The fumes from your over-heated mixtures sound
really dangerous.

ALSO - The “cautions” printed on the label of the hardeners about
danger to the eyes are generally understated to what I consider a
criminal degree. Someof these hardeners will produce permanent
blindness in mere seconds. Don’t be careless about your eyes. There
is no first aid or second chance with the stuff.

Good Luck,
Marty in Spring-like Victoria

You could be experiencing a surface to volume heat problem. This is
a common problem in scaling up batch processes like this.

Mixing a small amount of epoxy on a piece wax paper has a high
surface to volume ratio, and the contact of the wax paper on the work
surface could conduct the heat away. In the case of mixing in a paper
cup there is a low surface to volume ratio, and there is less
conduction surface to carry away the heat as with the wax paper.

You could try mixing the larger quanity on a piece of aluminum foil
against against the bottom of a thick aluminum pot.

Mike McKim

Another thought is to use a slower set, 24 hr.epoxy or more in which
the heat of forming bonds is spread out over a longer period of time
resulting in less heat production per unit time.

Mike McKim

I have always mixed epoxy (and for years used a great deal of the
stuff) on a sheet of aluminum foil, wrapped around and taped to a
flat surface ( in my case, an old cassette box or a cottage cheese
lid) . I used the “high-tech” measuring system mentioned earlier:
squeezing out a circle of resin and hardener of equal sizes. Very
easy to mark circles on aluminum foil. Then since viscosity may
differ in resin and hardener, holding it up to eye level and
compensating by a drop or two when one “circle” was higher than the
other (usually the hardener was thicker and therefore higher: so
adding the “drop” to the resin). I think I started out using
aluminum foil because I could mix the epoxy with a palette knife,
which I still think is the absolute best way, at least for me. Over
the years I have probably used gallons of epoxy, and the only times
it failed to set were when I knew I had been sloppy in my
proportions. A little heat when curing is always good: I use a
swing-arm lamp with a 60 watt bulb, pulled down to about 8 inches
above the pieces setting. (away from flammable papers and objects,
obviously).

I would think the wax could too easily scrape off a wax cup, and
many plastics could potentially be partly soluble in the resin, thus
contaminating it. Though there are plastic cups sold specifically
for mixing epoxy, and epoxy often comes in plastic bottles, I don’t
know what kind of plastic they are made from.

Epoxy 330 and Epoxy 220, made by Hughes, are old reliables, and
designed specifically for jewelry. Why not use them? 330 is the
clearest. 220 is amber colored but is stronger than 330. Both are
much better than the hardware store variety, and are available from
every jewelry supply house. They come in both small tubes for
occasional users and in bottles of various sizes. They also have a
very good shelf life. Rings and Things (mnetioned on Orchid before)
also makes up their own epoxy for bulk users, at lower cost. It is
very strong, is somewhat amber in color, and has a slower set time,
which is very handy if you are setting up lots of pieces. Generally
the slower the set. the stronger the epoxy. It is not as liquid as
the Hughes epoxy, therefore a little harder to measure. Have to
scoop it out (with a palette knife!) onto the aluminum foil, then it
fills the circles as usual. Shorter shelf life, about a year.

I don’t know if other epoxies would behave in the same manner, but
I’ve had good results mixing Rio’s Low-Viscosity Epoxy in little
graduated medicine cups. A dozen of these came with the kit and were,
of course, quickly used up. After a little searching, I located the
cups in good quantities at a nearby Hobby Lobby in the model-making
department. The really nice thing is that, since 1/4 oz. of epoxy
must be mixed at a time (with this kind) and it’s a 2:1 ratio, the
cups are graduated just right to yield consistent results: they
include lines for 5cc and 7.5cc. Furthermore, the plastic has never
interacted with the epoxy.

As for other epoxies, I tend to mix them up on whatever scrap of
cardboard I have handy. It’s not precise and won’t work for large
quantities, but it’s good for the occasional small job.

Cheers,
Jessee Smith
www.silverspotstudio.com
Cincinnati, Ohio

The aforementioned measuring cups for epoxy or anything else, of
specific material that will not stick nor contaminate, can be
ordered from Lee Valley - a most wondrous and satisfactory company
for many things from woodworking to gardening. I am a long time,
very satisfied customer, usual disclaimer.

  Mixing cups.  One ounce (30cc) polypropylene cups (impervious
  to shop solvents, thinners, paints, and epoxies) for accurate
  mixing........ Graduated in both metric and Imperial measure. 
  Pkg. of 100.  Item 56Z82.02 $2.95

Do yourself a favor and request catalogs. They’re marvelous! (But
addictive.) 1-800-871-8158 or www.leevalley.com

Patricia