HOW TO COLOR PLASTIC RESIN PRODUCTS
"IN THE MOLD"
You can paint plastic in the mold, save time
and materials and get better results than painting
A quick demonstration of in-mold
painting: epoxy resin cast into a plastic
butter-tub lid. The resin picks up the painted
can apply surface color to castings made from any liquid
plastic resin such as Polyester, Epoxy, or Polyurethane
Plastic at the same time you make the casting.
is best to use a rubber mold for this technique.
Polyurethane molds are preferred - they won't be harmed
by spray paint, and the paint can be evenly applied to
the mold. Silicone molds will also work, but since
Silicone repels some types of paints, you may not get an
even coat. Latex rubber molds will work, but the
solvents in some spray paints may damage the mold.
extremely easy - simply spray paint your mold with the
color of your choice before you pour in the liquid
casting resin. You can use acrylic or oil base spray
paints. Do not use a release agent - in most cases the
spray paint will also act as a release agent. (You can
also apply paint with a brush or even a rubber stamp if
the paint dry, and then mix and pour the liquid resin as
usual. As the resin cures, the paint on the surface of
the mold will actually become part of the surface layer
of your plastic casting.
the plastic has cured, remove it from the mold. The
surface layer of the casting will be the color of the
you want to test this technique and see how well it
works before actually using one of your molds, try this:
a plastic lid from a grocery product that has a colorful
design on it. Lids from butter tubs are ideal. (The lid
should NOT be made from styrene if you are using
polyester resin.) Mix and pour the plastic resin of your
choice over the colored design. Let the resin set, and
then peel the cured plastic off the lid. The result will
be a plastic casting with a high quality reversed image
of the design embedded in the surface. Rub over the
design with your fingernail and you will see it is much
more durable than any type of painting would be.
can make designs like this by painting, silk screening,
or rubber stamping images onto the surface of your mold,
before pouring the plastic resin. You can also use
inkjet or laser-printed images - see this
are several advantages to in-mold painting:
The color layer in your casting will be very durable -
it has actually become part of the plastic. It is much
more durable than it would be if you cast the product
and then painted it.
If you had previously been coloring your entire batch of
plastic resin with color pigments, you will save a lot
of money. By spray painting the mold, you only color the
top layer of the casting, not the entire casting.
The finished casting will appear to have a very even
coat of color, even if you didn't paint the mold evenly.
You can also decorate the surface with other materials,
using similar techniques. Try spraying a mold with a
clear acrylic spray and then immediately dusting it with
glitter or fine sand, for instance. The surface of your
finished casting will include the glitter or sand.
You can use spray paints such as "chrome" or "brass"
paints to get the look of metal. Or use the new
"granite" or "marble" spray paints to get those effects.
a PDF source list
Includes 26 suppliers of all mold making and
casting materials mentioned in ALL the demonstrations on
this web site, including silicone rubber, polyurethane
rubber, latex rubber, polyurethane plastic, epoxy resin,
polyester resin, molding clay, foam board, release
agents, pottery plaster, Hydrocal, metal powders, other
plastic resin fillers, and gelatin molding compound.
With company names, addresses, phone numbers, and web
sites. Downloads to your computer as a PDF file.