RESIN, CATALYST, COLOR
These three materials form the basis for all clear resin projects. The resin itself, EP4101, is a clear liquid
syrup with a sweet smell. The catalyst,
EP4920, looks like water and is the active ingredient which converts the liquid
resin into a hard, clear plastic.
Colors are available in transparent, EP7701, and opaque, EP7702, and
even a Glow-in-the-Dark. Decorations
can include materials such as glitter, metal powders, sea shells, baby teeth,
coins, fishing flies, etc.
MIXING
Mixing is generally done in paper cups with wooden sticks. For small projects, visual measurement using
graduated paper cups is generally close enough; catalyst is proportioned at a
starting rate of 10 drops per ounce of resin.
Mixing must be thorough. Mix
until all streaks are gone...and then some.
As an example, for a 11/2 ounce batch, fill a 3 ounce cup half full and
then add 15 drops of catalyst, mix thoroughly and pour. The rule of thumb, of 10 drops of catalyst
per ounce of resin, should be taken as the starting point when at 72 degrees
F. Sometimes conditions require
different proportions. As the projects
get bigger and thicker, less catalyst is used.
Also when ambient temperatures get higher, less catalyst is used.
MOLD
Many non-porous containers can be used as molds for the curing
resin. Examples include glass,
aluminum, polyethylene, wax, rubber etc.
Depending on the material, some molds can be used as is, whereas others
require release agents. For the
beginner, polyethylene molds (sometimes called Tupperware molds) are the best
choice because release agents are not required. With rigid molds, mold release wax is a good choice because wax can be polished to a high
sheen. Mold surface is an important
consideration. Factors such as
smoothness, shine, texture, hardness etc. affect the surface of the resin
casting. The resin conforms to the
surface of the mold and copies it. If
you want a shiny casting, you need a shiny
mold.
STEPS TO PERFECT CASTINGS.
First, analyze the mold and estimate how much EP4101 resin is
needed. For example, fill the mold to
the required level with sand or salt, and then pour it into a mixing cup. If the sand half fills an 8 ounce cup, you
need 4 ounce of resin.
Second, if your project is thin (1/4” thick or less), measure out
4 ounces of resin; add to that the color you desire; then add 40 drops of
catalyst. Mix thoroughly. While mixing, repeatedly scrape down the
walls of the mixing cup and the sides of the mixing stick to eliminate any
unmixed residues.
Third, pour the mix into the mold and allow it to cure
overnight. The curing resin is
sensitive to its environment.
Temperature and humidity will affect the cure. For best results, cure the resin at a steady room temperature of
72 degrees F and low humidity.
Fourth, remove the cured
resin from the the mold. Oftentimes,
the casting will fall out of the mold by simply tapping or bouncing the mold
against a table top. If the casting is
stubborn, place it in a refrigerator for a few hours; then pour warm water over
the mold (not the casting). In this way
you can expand the mold, which allows more room for the casting to fall out.
SURPRISES
This resin shrinks during cure.
The bigger the casting, the more noticeable it becomes. Shrinkage occurs during the “jello”
stage. If the casting pulls away from
the mold during this stage, the mold is no longer able to control the surface
and the surface of the casting becomes wrinkled and inferior. Click here to read about polishing these wrinkles away.
EP4101 is an air-inhibited resin which means that it does not want
to fully cure when in contact with air, or more specifically oxygen. The cure is inhibited by air. If a test tube were filled with catalyzed
resin, the resin in contact with the glass would cure rock hard, but the resin
on top which was open the air would appear soft. Eventually this dries out by itself.
EP4101 exotherms during cure.
This means that heat is liberated and the resin gets hot during
cure. If overheating occurs, the resin
can scorch which results in an undesirable amber color. Using too much catalyst accelerates the cure
which in turn speeds the temperature rise.
Overheating is undesirable.
Control it by: not overcatalyzing, keep ambient temperatures at 72
degrees F, keep layers thin, etc.
SAFETY
Chemical should be handled with
respect. Exercise common sense hygiene
and ventilation.
CONCLUSIONS
These general instructions are sufficient to get you started on your
first projects. If further information
is required, Eager Plastics has a wide selection of books and reprints dealing
with this subject or call for advice
