Fresco painting

Fresco is that type of wall painting done with mixed colour pigments or diluted with water, lain out on fresh plaster, using lime as the white colour. The fresco technique is based on the property of lime that united to river sand forms, drying, a plaster with a golden and crystalline surface in which the colour will remain completely incorporated and completely and indelibly fixed. Such plaster is made up of two layers: L’Arricciato and L’intonachino. The first is applied directly to the base wall, and it is made up of one part of lime, two parts sand and if necessary water. Once l’arriccio is dry the preliminary design, the sinopia, is traced on it.

On this base a layer of plaster is lain, intonachino, a mixture of fine sand, lime, marble dust and water, on which the colours are lain. The colour is rigorously lain on the wet plaster, from which the name "fresco" comes and must belong to the category of oxides, so as it does not interact with the reaction of the carbonization of the lime. The colours diluted in water must be a precise consistency, if they are too diluted they lack in power, if they are too dense they do not penetrate well.

The final touch is made with tempera paint and it is carried out dry, a secco, for this reason the retouching, with time, disappears, while the colour given a fresco, thanks to the chemical process of carbonization for which the lime incorporates it, ensures that the work remains more or less unaltered over time.

In the pictorial phase the difficulty consists in understanding which the effective tone of the colour will be, it is necessary to consider that when the colours dry they lighten, also the bottom of the lime which is light grey when it is wet, becomes white when it dries causing an alteration in the tonality of the colours.

It is necessary to start the work from the top to be able to catch eventual dribbles and avoid that the finished parts are dirtied.

Mosaics

In the mosaic technique the painting is realised bringing together many fragments, tesserae, which can be of various materials, stone, marble, ceramics, or vitreous paste.

The most common work procedure consists in covering the surface with a first layer of arriccio plaster often made up of lime, sand and water, which is used to even up the wall, then with a more external layer, made up of marble dust, slaked lime and pozzolana cement, in various layers, on the last of which, you can apply the tiles manually.

Generally, they are set out first in two or three lines following the outline of the forms drawn, subsequently the inside is covered marking the style of the representations. The tiles are prevalently square in shape, based on the picture to be painted, they can be triangular or oblong.

There are two methods for the application of the mosaic, a direct method in which a charcoal drawing is carried out on the work surface, to which a layer of binding material is subsequently added to the work zone the tesserae are lain out starting from the biggest, and then the smaller ones are applied, working from the outside toward the inside, at the end you apply a layer of cement for the connection of the tesserae which is removed after drying. In the indirect method the materials are attached the wrong way around on a temporary base surface, so the whole support is attached definitively, and you remove the temporary base.

The picture can also be executed directly on the binding material. A preparatory drawing is executed on cardboard, on which the principle lines are sketched on a sheet of flimsy paper, so obtaining the positive cast. Overlaying another piece of tissue paper on the positive cast turned the other way around it is retraced tracing the lines with printer’s ink, to the zone obtaining the cast in negative. This is lain over the excavation, making it stick to the binding product with light pressure of the fingers so as to leave it printed, once the paper is removed, the part of the picture corresponding to that zone.

In the case of a realisation on an already refined wall, a scraping of the wall corresponding to the size of the mosaic to be realised is carried out to a depth of about two centimetres. The surface obtained must be irregular enough to allow the binding materials to take hold perfectly. Having dampened the surface in question, the binding solution made of cement, slake lime and water is distributed in a first zone of the scraping, the size of which varies in function of the setting time of the binding solution, the difficulty of the piece to be realized and the speed of the work of the mosaicist.

In the west, the maximum expression of the technique of the mosaic was reached in Roman times with the use of tesserae in vitreous paste. With Christianity, the mosaic substituted painting of walls in the churches, in particular in Ravenna and in Venice, Byzantine art produced magnificent mosaics in which the inclination of the tesserae is methodically used in relationship to the origin of the light to highlight colours at their maximum.

Cercamic murals

Ceramic tiles are sheets in various formats and of different sizes, obtained from clay pastes, sand, other natural substances, water and baked at a high temperature. Most Italian tiles are made by pressing, the phase in which the paste, in the form of a semi-dry powder, is compressed between two surfaces. This operation gives the desired form the correct consistency and resistance to the product. The paste of the primary materials is shaped in the form of a continuous tape which is subsequently cut. After, using the rapid drier with hot air, the paste liquid of the product is eliminated.

The process of decorating ceramic tiles, comes after the first glazing of the rough product. The first operation is the enamelling, which is carried out by immersing the tiles in a liquid solution of enamel, or using an airbrush. The enamel used is made of glass, matting and melting and is used to prepare the tile to accept the decoration that will be placed on its surface.

The decoration of the ceramic tiles is carried out using specific colours, obtained by mixing mineral or metallic oxides, together with the melted materials, which are used proportionally based on the temperature of the second glazing.

White tiles are usually used in a single glaze. To execute a precise decoration you must effect the drawing in the guidelines with a pencil on the tile, so as not to allow smudging and errors. The colours can be overlaying, semi-overlaying, but also raised, and they are applied directly to the tile. The decoration techniques adopted can be different, from hand applied decorations, like those realized with a stencil or with a sponge. In the first case, you will have to trace the drawing previously made with a pencil decorating it with brushes of different sizes, in other cases, on the contrary, you proceed respecting the predefined lines inside the print.

In case of error, it is possible to remove the colour using cotton wool, soaked in hot water. Once the decoration is complete, the tiles are inserted inside the specific ovens, able to maintain a constant temperature of 920/950° C, for about 8/10 hours, with a further cooling period of 18/24 ore.

Generally, in the case of the mural, the artist creates some drafts of the whole piece in advance at a reduced scale and other sketches, indispensible when the work is to be presented to a buyer, for the details in a natural scale. A spolvero pad, riddled with holes along the edges of the final draft, allows you to transfer the drawing to the ceramic surface using a tissue swab filled with graphite or charcoal powder without losing the proportions.

With the drafts, the artist defines the composition and prepares the next pictorial development at the same time.

On the pencil drawing lines, the artist works with ceramic paints that will be definitively glaze fixed in the oven.

Finally, the tiles will be assembled one by one, and placed on the walls with different procedures, with cement glue or on special metallic structures in aluminium.


Torna su

Joomla! Debug Console

Session

Profile Information

Memory Usage

Database Queries