Molding Plastic Parts

Make Your Own Molded Plastic Objects
SULPHO-PLASTICS

This plastic is particularly adaptable for making moulds and light castings requiring tensile strength but
very clear outline. It may also be used for making ornaments and novelties. However, as this is
flammable, do not use for ashtrays.

While the name would convey the thought of plastic sulphur, which is an unstable allotropic form of
sulphur, this is not the case, as the sulphur acts as a bond to hold the filler together and forms a stable
material.

Interesting marble effects may be obtained by varying the filler used; and by substituting a small
quantity of chalk to replace some of the graphite, a very pleasing glazed surface marble is formed.
As long as the graphite is retained as a filler, this plastic may be electroplated and forms a very
economical base for such work.

FORMULA: Mix thoroughly and smoothly together 25 parts of GRAPHITE and 75 parts SULPHUR
and place over heat. As soon as the mass has melted and runs like water, remove from the heat. In any
case, a temperature of 235 degrees F. should not be exceeded. If heated about 250 degrees F. the plastic
will form a rubbery mass and will have to be cooled and reheated. In this liquid state the plastic is ready
for casting and may be poured into smooth surfaced moulds.
N.B. to heat this mixture properly, a good even heat is necessary. Should the heating be done by flame,
the container should be placed in a sand bath to insure an even heating surface. The cast-iron top of a
heater or stove is excellent.

EQUIPMENT: The only equipment for the above that is required is space enough to work in, a stove or
heater, a pan to heat the mixture in and a bench or table.

PROCEDURE: Before making any casting you will need a pattern. After choosing a design that fits
your need, your next step is to make the mould. Then you may start into production. If your produrequires any holes, threads or machining, this may be done in the same manner as in working with a
metal casting.

Always think of your castings as metal, for they have metallic properties, i.e., conduct heat, electricity
and can be electroplated. In fact, the most valuable quality of Sulpho-Plastic is the fact that it can be
used as a metal substitute. This permits you to make products that look and are as good and even better,
in some cases, than a true metal. For instance, to make a chrome plated metal lamp base or other metal
casting would require foundry equipment and machine shop work and in all, a process miles out of the
reach of the small manufacturer. However, with our plastic, a lamp base, similar in all respects, may be
made for a fraction of the other cost.

ELECTROPLATING: While this can be done at home with very little equipment, it is advisable to have
it done by a commercial electroplater, who does it very cheaply and much more efficiently.
Electroplating is only used on expensive replicas and is not advisable for a start.

DESIGN: The number and variety of articles that can be manufactured from Sulpho-Plastic is practically
unlimited and to make a complete list would be impossible. However, any article of reasonable size and
simplicity of design may be cast by using an original or purchased article for a
pattern or model – or an original design may be patterned in clay and used to make a mould. It is
advisable for the beginner to choose a simple article for a start, preferably solid.

MOLDS: Moulds may be made of metal or plaster of Paris. Metal moulds, however, require a great deal
of skill and equipment to produce. Therefore for the beginner, it is advisable to use plaster of Paris.
To make plaster of Paris moulds; first obtain a box, wood or cardboard will do; about an inch longer
each way than the article to be cast. Coat the inside of the box and the item to be cast very thoroughly, yet thinly, with a mould release agent, stearine or sweet oil. This acts as a lubricant and the plaster of Paris will
not adhere to either the box or the article, if the oil is evenly distributed.

Next make a thick, creamy mixture of plaster of Paris by sifting the plaster gradually into the
water, stirring constantly to prevent lumping. Let this stand a few minutes to allow the air bubbles to
escape. Pour mixture slowly over pattern in this box to about double the thickness of the pattern.
Allow several hours to dry, then remove. If the stearine or sweet oil was applied properly, this will be
easy. When the mould is thoroughly dry, give it a coat (thin) of shellac and repeat in 12 hours. Mould is
now ready for use.

MOLDING: First and foremost always make sure that you have lubricated your mould with beeswax or
stearine. Place moulds on a reasonably level surface and pour the sulpho-plastic into the mould, quickly
and smoothly. Do not pour from a height, as this will break the lubricant and leaves blemishes on the
casting. Plastic must be poured quickly to prevent cooling in folds and thus making a poor casting. One
of the big assets of sulpho-plastics is the fact that it dries and hardens almost immediately. There is no
long wait for casting to dry.

Share this: