Moulding & Casting

Which impression material for which project?

Which impression material is right for you and your project depends on several factors: How many casts do you want to make? How durable does the mould need to be? What do you want to mould? How big do you want the mould to be? What material do you want to cast with? Do the impression material and the casting material match? Ask us if you need advice on choosing the right moulding material!

Mould making with different impression materials

Most of the time, a fixed or flexible mould is first made as a negative mould of the master model, which is later poured out. In bronze casting, the process is more elaborate, there are more intermediate steps of positive and negative moulds. Different materials are suitable for mould making: Silicone, often also called silicone rubber, Alginate, latex, moulding sand, gypsum or clay.

Silicone, alginate and latex for flexible moulds

Flexible and elastic materials are necessary to be able to mould undercuts in the initial object (positive). Silicone is most commonly used to make 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, plasticine 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 be made not only of impression silicone but also, for example, of alginate, a natural product made from algae, or latex, a natural product made from rubber. These materials are particularly suitable for body impressions or when only a few casts are to be made. With latex, it is often even possible to get by with a one-piece casting mould for moulding small figures, as this can be pulled off the positive like a glove.

Plaster & Clay for Rigid Moulds

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

Support moulds, substructure & fillings

To make support moulds for flexible casting moulds, for example, Gips can be used. Very stable support moulds, but much lighter than plaster moulds, especially for large moulds, can be built from epoxy-casting-resin with fibre added – they can even be screwed.

Casting resins: Plastics, wax, gypsum, cement, concrete

Gypsum, cement, concrete, Wax or Clay can be used as casting compounds, as can 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.

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

Bronze casting, tin casting, lead casting

With pewter and lead you can cast small figures relatively easily, even in your workshop or studio at home, as these materials have a comparatively low melting point (pewter 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 thus has a much higher melting point. Pure copper, for example, only liquefies at 1084°C. The casting 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 specialist workshops. However, many of the preparatory steps can be done well in your own studio. If you have a suitable room, electric melting furnaces also offer the possibility of casting small bronze sculptures yourself.

Don't forget release agent!

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

Pigments & practical helpers for moulding and casting

With pigments many casting and impression materials can be coloured. At bildhau you can of course buy many things besides casting and impression materials, what you need for your work, e.g. measuring cups, scales, vacuum pump, vessels for mixing, spatulas for stirring etc.