Disegno dal vero – Zeichnen nach Modell – Tiles 2

Sabrina Kleiner
Restaurierung, Kunsttechnologie und Konservierungswissenschaft

“Our pupils shall not simulate lights and shadows, or represent the relief in any way, yet, but only colour the various parts of their interweaving, so that they may become acquainted with the intelligence of standard colour in the various industrial arts.”

*Original Language: „Gli alunni nostri non devono ancora né simulare la luce e l’ombra, né rappresentare in nessuna maniera il rilievo, ma solo tinteggiare le varie parti de‘ loro intrecciamenti per iniziarsi alla intelligenza del colore convenzionale nelle varie arti industriali.“ (Boito 1897)

Camillo Boito (1897) I Principi del Disegno e gli Stili dell’Ornamento. Urlico Hoepli Milano.

“Ceramic tiles are part of a wide variety of clay products which may be used for wall or floor finishes. Ceramic (greek: “Keramos” = clay product) can be divided in either “Feinkeramik” or “Grobkeramik”. This distinction comes into presence with the production process. If the grain size does not exceed 0.2mm, which is the case for these tiles, the product is considered “Feinkeramik”. […] Clay found in nature needs to be modified according to the specific product or recipe. A mixture of different clays, the addition of quartz sand/firebricks and other minerals leads to a primary ceramic mass. Defining and measuring water content of the primary mass is crucial for the next step: molding.
A lower water content from 5-10% leads to dry molding. High pressure is used to fill flat lying molds with a pulver, dry mass.
Masses with higher water content from 10-25% are usually processed with an extrusion press. The machine produces a string where tiles are cut off of (for “Grobkeramik”).
Contents of 25-40%(cap) are typically poured in molds. After molding, the mass starts slowly drying leading to a loss of the initial water content. The higher the loss, the higher the deformation of the tile. To preserve their shape and harden them, the next step is needed: burning.” (Martin)

“Glaze is applied to the face of the cold tile either before the first burn or after, which gives the tile a glass-like coating and makes it more durable. Commonly, the tile is glazed after the first burn and therefore needs to be burned a second and final time. The temperature depends on the burning point of the used glaze. In the case of the exemplary ceramic tile mosaic, the glaze is painted on the tile with a paint brush. The entire tile can also be glazed in one colour.
Glazes are for instance made out of quartz, dolomite, and various metal oxides, whose compounds are used for ceramic colouring. Examples for this are iron (yellow, ocre, red or dark brown) and cobalt (blue, dark blue or purple).
Traditionally, a mosaic is a coherent image or pattern, which is laid with small pieces (10 – 20 mm) of stone, glass or ceramic, it is held in place with mortar, and it is usually integrated in an architectural context. The definition has slightly changed, because nowadays a mosaic is defined as any image or pattern made from multiple pieces.
To lay the colourful ceramic tile mosaic from the example, a small amount of tile glue or mortar is put on the surface or is directly applied on the rough bottom side of the small pieces. Then, the ceramic tile shards are placed on the surface. The differently sized joints are filled with mortar and the access mortar is wiped off.” (Sabrina)