Thursday 28 March 2024

automatic translation

Thursday 28 March 2024

automatic translation

    Techniques for decorating glass - Part Two

    We continue our path for the decoration of cold glass by briefly illustrating other techniques: painting on glass, the use of enamels and lustres and screen printing.

    Glass painting
    There are three techniques for painting on glass.
    1 - The traditional stained glass technique that uses colored plates: the contours and shadows are marked with the brush; Grisaille is then used which, when cooked in the oven, is irreversibly fixed to the glass.
    2 - Painting with fusible colored, transparent or opaque enamels, which are fixed by firing in the oven.
    3 - Cold painting with colors that are fixed by drying of the binder and without firing. The latter can be easily removed by abrasion.

    The glazes
    They are easily fusible glasses, therefore containing many low-melting oxides such as those of lead, boron and bismuth.
    They are colored with the same oxides and compounds used for glass, but in much higher concentrations, given the thin thickness with which they are applied. They can be both opaque and transparent.
    The colors for painting are therefore composed of an easily fusible (melting) glass, which serves to anchor the color to the surface of the object and of a coloring preparation. The mixture of the two components in a very fine powder, suspended in an oily organic binder.
    The colors are applied to the glass by brush or spray, left to dry and then heated in a muffle at a relatively low temperature (about 500 ° C) to avoid deformation of the product, until the flux melts.

    The objects decorated with enamel are very delicate. Enamels have the defect of being easily attacked even by acids and of detaching from the support due to the different thermal expansion.

    The lustrums
    Lustres are a particular type of enamel, which allow you to bring very thin films, shiny or burnished, of non-oxidizable metals such as gold, silver and platinum to glass.
    With this technique, blown objects such as the edges of glasses are gilded with yellow gold (pure gold) or white (platinum).

    Screen printing
    With this technique, the decoration is impressed through a cliché placed on the surface of the glass. To do this, a metal frame is used on which a synthetic fabric is stretched (originally it was made of silk, hence the name of the technique).
    The cliché is obtained with a photo-mechanical system that allows the meshes of the fabric to be opened in the parts of the design to be reproduced.
    A low melting glass, pulverized and mixed with a pigment, is placed over the frame and passed through the open meshes of the fabric with a rubber spatula.
    We then move on to drying, the glass is placed in a muffle at the temperature necessary for the melting of the enamel.

    Source: glassway.vda.it

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