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Casting today

Historical notes

Lost-wax casting with ceramic shells

The system of lost-wax casting with ceramic shells is a further development of the traditional systems of artistic casting.
Founded in the United States in the 1970s for high precision steel casting of components for the aeronautics and space industry, it has been adapted to make artistic pieces.
This allowed the quality of artisan handcrafting skill to be combined with the use of modern materials and technologies.
The transformation of a model into a bronze sculpture takes place through a process made up of several, quite distinct phases.

Original created by the artist Antonio Sgroi
different colours and shades of bronze


The mould made on the original model (which may be of any material, such as clay, plasticine, wood or metal) can make one (or more) wax reproductions.
It consists of a silicone rubber sheet (which is a very elastic, strong material), which perfectly adheres to the model, copying it exactly. The rubber is encased in a plaster sheathe that gives it rigidity and consistency.

Phases of applying clay and plaster casing

The clay is replaced by the silicone mould.


The intermediate wax prototype is made in the mould.
It is made by pouring liquid wax in the mould until it forms an even thickness. When the wax is solidified, it is extracted from the mould. Each single wax piece is meticulously worked by hand to eliminate any imperfections.
After the sculpture is retouched, wax bars are applied that serve as pouring channels and vents. They are assembled in each case depending on the object’s form and particular issues, always in different ways so as to allow the proper flow of the metal and venting of gases during casting.

Pouring of the wax

Opening the mould with the solidified wax

Original and wax copy

Retouching wax models

Application of outlet and supply channels

Ceramic covering

At this point, the wax model is immersed in a liquid mixture of ceramic material to make a shell thick enough to contain the bronze’s pressure.
The forms, made with the ceramic material, are extremely thin and lightweight, with high strength and low deformability. The bronze’s surface, made with a ceramic shell system, is smooth, compact and structurally strong thanks to the form’s very low thicknesses, allowing for a rapid cooling of the metal.
Once the shell is dried, it is put in an autoclave where, through the high pressure application of steam, the wax is extracted from inside (hence, the term “lost-wax”).

ceramic soaking

phases of ceramic application


Empty shells are heated in the kiln. They are extracted still glowing hot and filled with cast metal. Once they are cooled, the ceramic covering is broken into pieces by vibration and shot blasting and the casting channels and vents are cut.

melting pot preparation

earth in which the ceramic models are placed

the bronze is poured into the ceramic models

the ceramic material and bronze cool

Refinishing and patina

Once the piece is cleaned, the marks of casting are removed with files, cutters and burins,
eliminating imperfections and accentuating certain details.
The final operation is applying the patina or colouring the piece. This is done through various oxidization processes with the aid of thermal and chemical treatments that make for different colours and shades of bronze.

the ceramic material is removed from the bronze positive

sanding cleans ceramic residue off of the bronze

immersion in pigmented solutions


blend applied by hand


Pictures taken in Merighi Arte laboratories, published in the "Il grande libro della scultura" [Big book of sculpture]; publisher: Demetra

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