Mixing Epoxy Resin and a short
explanation to pot-life
On this page I don't want to
bother you with more chicken soup - but we stay in the kitchen and grab
two glasses of honey! Mixing Epoxy is far away from mixing paint, oil,
or any other fluid what we are used to mix ... Martini, Tequila ....
30% of all Epoxy screw ups are in measuring and mixing.
Since you found already your
perfect epoxy from the perfect supplier you have it in front of you
read the technical data sheet - there you find the mixing ratio - be
careful in the difference between "mix by volume" or "mix by
weight".
Get your plunger , measuring cup
and your wife's kitchen scale ! Big and heavy container are mostly a
nightmare if you just need to mix 4 or 6 oz - try to refill in more
handy container - 1 gal size is a lot easier to handle and you waste
less.
If possible use graduated cups ( not
the ones with a wax liner as the wax will be scraped off during mixing
the resin ) My idea is to fill first the Resin and after that the
Hardener - if you got too much - you can fill to the next mark to get
an equal mix - and it is better to have a bit ( don't get me wrong on
the bit - I mean max. 5% with bit ) more hardener than resin. Double
check on the scale if the relation fits - after that, pour the whole
stuff in a handy mixing pot - something which lays good in your hand
and has no corners on the floor. Mix it well through! Rule of thumb
would be 1 minute for each 2 oz (50 ccm in metric).
Why so long ....?
Get your two glasses of different
honey ( to make this example easier , get a light and a very dark one)-
take a fresh mixing pot and try to measure correct - you will see it is
not as easy to get to the mark as you thought - now if you have the
honey mix, pour it in a glass where you can look through
Write down the time. Get the mixing
stick and start mixing the honey. Mix till you see no more lines in the
honey from one or the other kind. Don't forget the edges at the bottom
of the glass and you will see how long it will take till you get
all
mixed well. If you are done, take one more look at your watch. It will
take even longer to mix your resin.
My Resin is too
hard to pour!
As
lower the temperature as harder/chewier
your resin gets. Especially on 100% solids Resins. Look if the
temperature in your workshop where your workpiece is , is still
okay to apply your
resin. If you just stored the resin on a too cold place - like concrete
floor - you can set your container in warm water ( 100 F / 35 C). Don't
take too hot water since it will speed up your Epoxies reaction and
shorten pot live. It will take quite a while to get more fluid. Here
your resin reacts as honey - as warmer it is, as more fluid it will
get. If you keep this in mind ... you should have no problems.
Pot live !
In your technical data sheet you
will find the pot live of your resin - 'Pot live' is the open time (
workable time ) of
the resin - how long you can play around before it starts to set - just
this is a very relative time. You must read on in your data sheet for
which amount this pot live is. As bigger your mix is as shorter gets
your pot live and as warmer your workshop is as shorter is your pot
live - somehow our supplier's don't write this together on the same
line. And it might make you wonder, if you have a resin with 30 minuets
pot live and mix 24 oz ( 700 ccm) and after 15 minuets you can boil
eggs on your resin. Try to make small batches, not more than 12 oz (
350 ccm ) to have enough time to mix it well and apply it without a
rush. If you tell me now you have to laminate a 64' boat hull and it
might take you a century with 12 oz cups - you are right - on big
surfaces, you need one person just to mix and a second person to apply.
If you have big batches, you can spread your resin right away after it
was well mixed over the glass. The bigger the surface is not allowing
the resin to boil up and gives you more time to apply/ work it.
It is a good idea to start on the
tricky parts with the fresh mix - hold your mixing pot in the hand and
let it not stay in the sun - if you feel it starts to get warmer, just
spread the remaining batch over a big surface. So you can make the most
out of the batch and the time. With time, you will get a good feeling
for your resin! So please don't mix your 1 Gal. resin at once and
wonder if after 10 minuets you reached the potlive of your mixing pot -
which is smoking on the floor.
Premix - or preactivate or
hotbatch ...refers
to a patch of resin which you mixed for a extended time till it starts
to react in your mixing pot - you will feel that its temperature will
rise.
This is not recommended if you are new with mixing epoxy and helps only
if you have a extreme time restrained job where your finished laminate
needs to be cured way before the normal 72 hour time window.
It requires a good feeling in your hand (temperature change of your
resin ) - and you mix the resin till it starts to cure in your mixing
pot - than you apply the resin as quick as possible (as long as it is
still fluid and just before it starts to gel) on your work piece and
spread it out swift and evenly - not recommended for beginner and has a
high rate of failure .
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