What is casting plaster and how are plaster casts made?

Casting plaster is used as a building or modelling material similar to mortar or cement, starting as a dry powder and is then mixed with water to form a paste which dries into a hard surface.

The traditional casting process involves plaster being applied to the original to create a mould. This mould is a negative impression of the original which is then removed and fresh plaster is poured into it, creating a copy in plaster of the original. Smaller castings are often poured as a solid by hand in a process known as gravity casting whereas larger sculptures employ the building up of layers to produce a hollow casting.

Mechanical casting can be achieved using centrifugal force, a C300 Centricast machine can be used to produce large numbers of castings with improved results when casting low melt alloys and pewter. Casting materials can also be coloured using pigments or replicate stone and metal finishes when combined with filler powders or when casting a modelling plaster or wax be carved and re-worked to the final form of the sculpture.

Casting Materials

Plaster

There is a whole range of casting plaster and modelling plaster to choose from, all with different setting times and measures of strength. We supply a range of plasters for a variety of uses. Our Prestia Classic Plaster is a very fine and fast setting dental plaster, our Basic Alpha Plaster is both dense and strong which can be used in combination with plaster polymer and the Modell Plaster is our hardest casting plaster which produces castings that are very finely detailed and strong. We also supply a Terracotta and Iron casting powder. This material, made in-house following our own formulation, produces unique casting properties. It resembles fired terracotta and makes cast pieces that if set outside, will eventually oxidise and begin to turn rusty.

Resin

Resin casting is a method of plastic casting where a mould is filled with a liquid resin and can be used for either small-scale, decorative castings or alternatively used in combination with fibreglass to produce large-scale hollow castings. We supply a variety of different polyester resin products, including clear casting resin useful for embedding or encapsulating, gel coat resin and general-purpose resin. We also supply a range of polyurethane resin and epoxy resin, our general purpose clear epoxy resin can be used for casting and embedding but is best suited to cold enamelling and coating and makes for a very good picture varnish. 

Cement

Our Ciment Fondu is an especially fine, high alumina casting cement that is fast setting and provides superb detail. Achieving its full strength in 24 hours, it is an extremely hard product that is ideal for outdoor applications. It can be traditionally cast with a sand aggregate or mixed to a malleable consistency and modelled by hand direct onto an armature. For those looking to create durable plaster like pieces for outdoors you can consider Secar 71 a brilliant white casting ciment used in the same way as our Ciment Fondu.

General fillers

These are finely powdered stone fillers primarily for use with polyester resin. Fillers are used for a variety of reasons such as for their effect, to improve opacity when using pigments or to bulk out the resin for economy and to reduce heat when casting large solid pieces. Other useful properties of fillers include improved hardness, scratch resistance and thixotropic qualities. As well as general fillers, we also supply metal fillers. These are fine metal powders designed for use with resins in the cold cast resin metal process, originally developed here at Alex Tiranti Ltd in the late fifties.

Resin sundries

To ensure that you get the results that you want when working with resin it’s always best to have the right equipment to hand. Laminating brushes, polishing tools and the right plastic moulds could be just the helping hand that you need to achieve the look that you are aiming for when working with resin. We also supply acetone for cleaning your materials after use.

Where can I get casting materials and casting tools I need?

Here at Tiranti, as the leading UK suppliers of sculptors’ tools, materials and studio equipment for carving, modelling, mould making, casting and restoration, we are well equipped for providing our customers with the best quality plaster and casting supplies. All of our casting products can be viewed on our website and if you have any questions or need any advice on modelling castings, then please do not hesitate to get in contact.

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