Moulding & casting

xxxMoulding is usually an intermediate step on the way to casting. The mould of an object, be it from nature, a sculpture, a plastic, a utility object or, for example, the human body, is taken from the original, the master model, with the help of a material that is often initially liquid and then cures to become elastic and dimensionally stable. In order to subsequently be able to cast without the mould changing, it is often necessary to build a supporting mould.

Through moulding and casting, objects can be developed, objects, sculptures, models, body parts or surface structures can be reproduced, moulds can be produced in larger quantities and objects can be translated into another material.

Which moulding compound and casting compound is best suited for which moulding depends entirely on the type of project, but also on the work situation. During casting, a liquid mass is poured into a previously prepared casting mould or casting form, which hardens due to different chemical processes.

The temperatures and humidity in the working area, for example, can strongly influence the setting time and curing behaviour of the individual materials. Silicones and synthetic resins are generally two-component systems that cure through a chemical reaction.

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Which moulding compound for which project?

Which moulding compound is right for you and your project depends on various factors: How many casts do you want to make? How durable does the mould need to be? What do you want to mould? How large should the mould be? What material do you want to cast with? Are the moulding material and casting material compatible? Ask us if you need advice on selecting the right moulding compound!

Mould making with different moulding compounds

In most cases, a solid or flexible casting mould is first produced as a negative mould of the master model, which is later cast. The bronze casting process is more complex, with more intermediate steps of positive and negative moulds. Various materials are suitable for mould making: silicone , often also called silicone rubber, alginate , latex , moulding sand, plaster or clay .

Silicone, alginate and latex for flexible moulds

Flexible and elastic materials are necessary in order to be able to mould undercuts in the initial object (positive). Silicone is usually used for the production of flexible moulds. There are many different silicones for different applications, e.g. heat-resistant when casting with lead or tin, skin-friendly for body impressions, modelling clay for quick impressions of small objects, etc. As a rule, at least two mould parts are used to make an all-round impression of a body. Flexible casting moulds can also be made from alginate , a natural product made from algae, or latex , a natural product made from rubber. These materials are particularly suitable for body moulds or if only a few casts are to be made. With latex, you can often even make do with a one-piece mould for casting small figures, as it can be removed from the positive like a glove.

Plaster & clay for rigid moulds

Of course, moulds can also be made from plaster or clay can be produced. These are then rigid moulds that usually have to be destroyed during demoulding.

Support moulds, substructure & fillings

For example, plaster can be used to produce support moulds for flexible casting moulds. Very stable support moulds, which are much lighter than plaster moulds, especially for large moulds, can be made from epoxy casting resin with added fibre – they can even be screwed together.

Casting compounds: Plastics, wax, plaster, cement, concrete

Plaster, cement, concrete , wax or clay can be used as casting compounds just like synthetic resins, e.g. epoxy casting resin , Polyester casting resin , polyurethane casting resin or acrylic casting resin , but also metals such as lead, tin and bronze.

There is a large selection of casting materials – they not only lead to very different results, but also place very different demands on the working method and working situation. Objects made from cast resins, for example, can be very light, even if they are large. Concrete sculptures always weigh quite a bit. You can cast detailed moulds with wax and plaster, with cement and concrete it depends on the mixture.

Bronze casting, tin casting, lead casting

With tin and lead, you can also cast small figures relatively easily in your workshop or studio at home, as these materials have a comparatively low melting point (tin 231°C, lead 327.4°C). Bronze, on the other hand, is an alloy of various metals with a high copper content (at least 60 %) and therefore has a much higher melting point. Pure copper, for example, only liquefies at 1084°C. The mould must be correspondingly durable and temperature-resistant. Bronze casting requires several intermediate steps of positive and negative moulds.

Bronze casting is very time-consuming, not least because of the high temperatures required to melt the bronze, and is therefore usually carried out in specialised workshops. However, many of the preparatory steps can easily be carried out in your own studio. If you have a suitable space, electric melting furnaces also offer the option of casting small bronze sculptures yourself.

Don't forget the release agent!

Release agents are used during moulding to protect the original object or the base material. They prevent the „model and moulding compound or mould (e.g. silicone mould) and casting compound or different mould parts from sticking together. This means that the casting mould is also protected from damage by the casting material. Depending on the material of the model and the moulding compound as well as the casting mould and the casting compound, use different release agents.

Pigments & practical helpers for moulding and casting

With pigments many casting and moulding materials can be coloured. At bildhau you can of course also buy many other things besides casting and moulding materials, what you need for your work , e.g. measuring jug, scales, vacuum pump, containers for mixing, spatula for stirring etc.

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