Moulding treasure trove
Centuries-old insects
and leaves have come down to us in a perfect state of preservation, sealed in
the resin of certain pine trees. We can imitate nature and capture the fleeting
beauty of a flower, a leaf, an insect or a starfish in clear plastic resin, a
remarkable product that is a man-made version of nature's fossil resin.
Seen on its own polyester resin seems nothing special — a
colorless jelly-like substance, which only acquires its solid state with the
addition of a special hardener. But even once it has hardened to glassy transparency;
it needs the beauty of an object sealed within it to bring it to colorful life.
Practically anything can be enclosed in this resin.
Photographs, stamps, coins, dried flowers, beautifully colored autumn leaves...
in this way holiday souvenirs, mementoes of a happy time can be preserved. They
can be turned into decorative pendants, paper-weights, doorknobs, a buckle for
a belt, cuff-links or ear-rings. When the light falls on them, they shine with
a rare luster.
Working with
polyester resin Before you begin to use this material learn all you can
about its properties and how to use it. Polyester resin, the hardener used with
it, and the special mould cleaner is all harmful to the eyes, skin and clothing;
so is the dust which is released when you rub down the finished object.
Precautions are necessary, especially if you are working with children near
you.
Should the polyester resin come into contact with the skin,
wash the affected parts thoroughly with soap and water. If you get any of it in
your eyes, mouth or nose, wash thoroughly with plenty of cold water and if
necessary go and see the doctor. Always work in old clothes and shoes in case
you splash yourself. During the hardening process, air the room well,
preferably keeping the windows wide open.
The materials The polyester resin, hardener, the mould cleaner, resin
solvent and moulds of various materials can be bought from most good
do-it-yourself or handicraft shops, or even from some large department stores.
If you don't want to buy a mould you can improvise by using
household utensils like egg cups, foil trays, ash-trays or dishes. Containers
made of glass, metal, Pyrex, are all suitable. As the mould must withstand a
certain amount of heat during the setting or "curing" stage
polystyrene containers are not suitable as they may dissolve. Choose a shape
with no awkward curves so that the casting will come out easily.
You will need waterproof sandpaper in various grades for
rubbing down, and metal polish for polishing the finished product.
If you are going to preserve fresh flowers then you must use
a hygroscopic separation agent — sensitive to moisture.
Like all handicrafts you will learn and get better as you go
along, so it's better to start with something simple and to buy materials in
small quantities. You will find full instructions on how to use the various
materials on the packaging, but here to help you is some general information
about the whole process. Casting an object in polyester resin is done in two
phases. You start by pouring a layer of resin into the required mould; this
will form the base for the object you are preserving, and is followed by a
second layer. For thin flat objects like a photograph, or a dried and pressed plant
or flower, the two layers together should not exceed 1cm (about ½in) and
ideally it should be a little less.
Make sure the mould is completely level, so the object to be
sealed in can be put precisely in position where you want it and will not move
about during the setting stage.
If you are working with flowers, leaves, insects, or
anything else which must be dried before being preserved, then you will need to
place them in a tightly sealed container with a drying agent (also bought in
handicraft or do-it-yourself shops). The drying process will take about a week.
At the end of that time, shake off the drying agent and any dust and your
object is ready to be cast.
You can now follow the entire casting process in pictures.
We used a pressed poppy cast in resin to make an attractive buckle. The top
picture shows the materials and tools you will need. The dried and pressed
poppy, all ready to use, moulds, a plastic beaker for mixing the resin and the
hardener, special mould cleaner or silicone wax, small brush, tweezers, and the
resin solvent for cleaning up. The second picture shows the poppy placed on the
mould with a pair of tweezers. The mould has been treated with the cleaning
agent, the polyester resin and the hardener have been mixed in the measuring
cup (quantities are given with the manufacturer's instructions). They have to
be mixed thoroughly but not stirred too vigorously or you get air bubbles which
will have to be dispersed. As you stir, the moulding resin turns pale green,
but this green tinge will disappear later during the hardening process. Leave
the mixture to rest for a while so that even the smallest air bubble has time
to escape.
Then pour the first or base layer into the mould. The
hardening process depends on the size of the mould and the temperature of the
room, but at a temperature of 20°C (68°F) the moulding resin should start to
harden after 20-30 minutes.
As soon as the layer has hardened and will not move when
tipped, place the object gently on its surface, keeping it in position with the
tweezers and a toothpick until it starts to stick. The third picture shows the
poppy being gently stroked with a finger to remove any air bubbles which may
have formed underneath it. The fourth picture demonstrates how the final layer
of resin is poured on top of the foundation layer. This is about 45 minutes
after the poppy was put in position. As you pour, new air bubbles may be formed
which you can remove with the toothpick — you'll see them rise to the surface
and vanish. Leave the casting in the mould until the next day and with resin
solvent carefully clean at once all the tools you no longer need.
To remove the casting from the mould, completely immerse the
mould in boiling water for ten minutes then immerse it upside down in very cold
water for ten minutes. Repeat these processes until the casting drops out of
the mould. Never chip away at the casting in the mould, trying to get it out.
(Resin hardens best when it is not in contact with the air, so cover the
casting with a sheet of waxed glass or a piece of cellophane while it's
setting.)
Once you've removed the casting from the mould, leave it to
set or "cure" for as long as possible at room temperature.
The fifth picture demonstrates the rubbing down process used
to get a smooth surface. This is done with moistened waterproof sandpaper. Dry
rubbing is dangerous as it releases a fine dust which could get into your eyes.
Rubbing down is done in four or five stages. You start with coarse waterproof
sandpaper until the surface of the casting is fairly smooth. You continue with
progressively finer sandpaper, until the lines made by the coarser sandpaper
are rubbed away. The best way to rub down is in two directions, vertically and
horizontally. During the rubbing process the casting becomes milky white and
quite opaque. When it is perfectly smooth it is polished with metal polish —
nickel chrome cleaner is ideal — until it is quite clear and transparent. You
then polish it with a soft cloth.
This polishing is repeated after about two hours when the
pressure on the polishing cloth should be steadily increased; the friction
produces heat which in turn provides the casting with its final luster.
The last picture shows the finished article—the unusual
buckle in position on a favorite belt.
General points If you are going to cast something thicker than 2cm (about ¾in)
then the time gap between the casting of the first and second layer must be
increased. For a thickness of 2cm (about ¾ in) allow 2-3 hours between casting
the first and the second layers.
You must wait until the first layer no longer releases any
reaction heat. The larger the quantity of plastic resin used, the more reaction
heat there will be to dissipate. If too much moulding resin is cast in one
operation, instead of in several layers, then the moulding will overheat and
will either crack, owing to the stress, or discolor.
If you are making pendants or mobiles, you will need to
drill a hole in the finished object. You can use a hand drill, but do not exert
too much pressure; just let the drill cut its way through.
Working with plastic resin is an exciting hobby which can
turn everyday things into something personal and precious. |