Filling of a historical mould © Staatliche Museen zu Berlin, Gipsformerei / Jürgen Hohmuth, Zeitort
Before a finished cast can be made available for sale, it has gone through an elaborate, highly skilled process which, depending on the size and complexity of the project, can take months of work. The path from the original to the replica consists of three main stages: the manufacture of the mould, the casting, and the final application of paint.
The first step is the creation of a ‘model’ that is archived as a true copy of the original and serves as the base for all further casts.
The plaster piece-mould is the technique that was traditionally used in the 19th century. A cast is taken from the archived mould in several steps. After the ‘negative’ has been filled and allowed to harden, the cast is finely sanded and given the finishing touches. The main advantage of this method is the durability of the end product, but it is extremely labour-intensive.
Today, moulds of original works are often made with silicone. This method is particularly suitable for very popular pieces. As a casting material, silicone is just as precise as the plaster piece-moulds but, unlike plaster, it is also elastic. One disadvantage is that the moulds have to be replaced after about ten years of use.
The latest technology used in replicating artworks is the 3D scan. A non-contact scanning device is used to capture a three-dimensional impression of the artwork which is then transformed into a virtual model made up of thousands of separate points. A 3D printer is then used to reconstruct the model, layer by layer. The 3D procedure is still very expensive, however, and unlike the traditional methods, the model requires some work afterwards. Its major advantage is that it makes it possible to create moulds of especially fragile works.
Following an in-depth analysis of the original work, the replica workshop always tries to find the most suitable technique for each cast. Sometimes the best solution is a combination of methods. To this end, the Gipsformerei and the Technische Universität Berlin have developed a hybrid casting method that unites analogue and non-contact technologies.