Lost wax casting

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Roman statue of Dionysus , made between 117 and 138 AD; exhibited in the Museo Nazionale Romano, Palazzo Massimo Alle Terme. The sculpture was made using the lost wax technique. The head's mouth was made using the copper damascene technique

The lost wax process is a molding process for metal and glass casting . One-piece molds are usually made. The models are mostly made of wax , but for some years now they have also been made of plastics. In the course of the process, both the model and the mold are destroyed. Hence, it is also referred to as the lost model method, sometimes also called the lost form method . However, since there are other, completely different shaping processes with lost shapes, the latter designation should be avoided.

Another name for the process is French cire perdue ("lost wax").

Work steps

  1. A desired object is modeled from wax. This is the model or wax model.
  2. The model is provided with sprue and ventilation channels (in foundries such models are also referred to as "the wax").
  3. The molding material is processed.
  4. The model is coated with molding material / investment material ; the green form is created.
  5. The green form is melted out; the mold cavity is created. In the case of water-containing molding materials, this is dried in the process; in the case of plaster models, vacuum drying is sometimes carried out beforehand.
  6. Depending on the investment, the form may be fired.
  7. Molten metal is poured into the mold.
  8. The metal solidifies in the form.
  9. The mold is smashed to remove the raw casting.

Variants of the lost wax process

There are two types of shapes, which are structured differently:

Block shapes

These include all molding materials whose binding agent is plaster of paris , e.g. B. chamotte or brick chippings . The wax models are provided with a gate and either immersed in the liquid molding material or the molding material is poured over the models. After the plaster of paris has set, the molds have to be fired for a few days in a drying oven at temperatures of up to 800 ° C, depending on their size.

Shapes with a shell-like structure

These forms cover the wax model with a shell made of fire-proof molding material. While the molding material is in liquid form in the above-mentioned forms, in this method the molding material is applied to the wax in one or more operations. The most frequently used molding materials for this are clays and specially prepared loams. For several decades now, quartz sand with water glass as a binder or other refractory materials such as zirconium and olivine sand with synthetic binders. The latter are often used in the jewelry industry, precision casting or investment casting .

Requirements for the materials

The model material must be able to withstand mechanical loads so that it does not break or be deformed when it is molded. It must be possible to completely melt the model material; this is especially true for precision casting. If the model is also to be produced using a mold, it should have little or no shrinkage.

The molding materials are diverse, but all molding materials should have a combination of the following properties:

  • Malleability
  • Fire resistance
  • Gas permeability
  • good disintegration after casting

The following are also required for precision casting:

  • Dimensional behavior
  • chemical stability

Gypsum-bonded investment materials disintegrate easily and release sulfur, which contaminates the cast metal.

It follows from the requirements that a number of materials can be considered, for example:


The principle of this procedure has been known for millennia and has been found at the latest since the 4th millennium BC. Application in the metal trade. From the 5th millennium onwards, important centers of metal processing were Bulgaria with its early copper mines, and Kestrel and Göltepe in Anatolia with one of the earliest tin mines and tin production in the Old World (4th century BC).

The process was also known to the indigenous peoples of Colombia and Central America , e.g. B. the Muisca ( Eldorado ). You used for this z. B. Tumbaga and shaped cult objects .

All important bronze art works of the early Middle Ages were created in this way.

Today, for example, the hood ornament of the Rolls-Royce (see Spirit of Ecstasy ) is made using the lost wax process. This process is also used in contemporary art , as the molding reproduces the fine modeling structures very precisely, as can be seen, for example, in the bronze sculptures by the artist Norbert Marten . The dental technology also uses this method.

Traditionally, in addition to the lost wax process in bell casting - in which characters and ornaments made of wax are applied to the "false bell" before casting - there is another method of labeling and / or decorating bells: the bell scratch drawing .

Work examples

The rich biblical ornamentation of the Bernwardstür , a two-winged bronze door in the west portal of Hildesheim Cathedral, dated around 1015 , the first cycle of German sculpture , part of the Hildesheim World Heritage Site of the cathedral and Michaeliskirche , and at the same time one of the main works of Ottonian art , was made using the lost wax technique manufactured.

Egbert Broerken , Emil Cimiotti, and Bodo Muche are among sculptors who have recently used the process.

See also


Web links

Commons : Lost wax casting  - collection of images, videos and audio files