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.