Various different techniques are utilised in the creation of our articles, and since certain terms may be less familiar we have decided to provide a brief explanation of some of them.
Oil gilding (Doratura a Missione):
In oil gilding a special size or glue known as missione is used to apply the gilding to small areas; this technique was used predominantly in the eighteenth century to embellish small parts of paintings.
First the ground of the panel has to be isolated with a few layers of acrylic colour, which is then sanded when the application is complete. The size made of linseed oil, resin and pigments must then be applied carefully in two or three coats, using a small soft brush. Nowadays there are also vinyl sizes which are quicker to apply since no pre-drying is required, but the final effect is less luminous. Once applied the article is left to dry partially (up to 12 or 24 hours) after which the gold leaf is applied. This is then pressed down using cotton wool so that it adheres perfectly to the surface, after which it is brushed with another small brush to remove any impurities.
As an application technique it is simpler, but is not suitable for large areas. Another drawback is the impossibility of burnishing. This technique is also known as doratura a mordente, or mordant gilding.
Water gilding (Doratura a guazzo)
This is the traditional and more difficult technique, which has been used since the thirteenth century by the great Italian and European artists. Gold decoration embellished the painting both physically and artistically, giving luminosity to the work and enhancing the colours of the painted part. In water gilding the gold is spread on the panel first, before passing to the actual painting. The panel is prepared by carving out the border of the area to be gilded, after which a gluey paste is applied and finally the gold leaf. The substrate used in the past was made of water, stiffly-beaten egg white and bole, a paste of very fine clay; today the composition has changed and normally two layers are applied. First a primer layer (called ammanitura or imprimitura) of hydrated calcium sulphate, also known as Bologna gypsum, Meudon white or Spanish white, heated in a bain-marie is applied. Usually 2-5 coats of this gesso are required, and it has to be sanded very carefully to leave the panel perfectly smooth. The next step is the clay bole, which is mixed with water and glue. The bole affects the final colour of the gilding, so that depending on the specific requirement it may be yellow (for bright gold), red (for dark gold), or black (for antique gold). Only when the panel is perfectly smooth can we proceed to the actual gilding, that is the application of superfine sheets of gold leaf, transferred with the greatest care from the paper base to the dampened panel using a fine knife (gilder’s knife) or a soft brush. Before this operation it is essential to spread a very fine layer of guazzo, or gilder’s liquor, a mixture of alcohol, water and glue. The guazzo is spread immediately before the application of the gold leaf. The sheets of foil are overlapped by a couple of millimetres, to avoid imperfections and gaps. The metal foil used can be of different kinds, from gold to bronze.
Purpurin: a very fine powder is sprinkled over the surface to colour and fill the cracks in the material. Depending on the colour (gold, silver or bronze) it can be used to enhance the craquelé effect or to even out the surface colour. It requires a substrate of size or missione.
Burnishing: this is performed once the glue has dried, and consists of rubbing the foil with a tool known as a burnisher (made of a wooden handle and a head in shaped agate). The rubbing serves to smooth the gold foil and make it shiny. Burnishing is omitted when special “antiqued” effects are called for. It should be performed in different directions, so as not to leave traces or streaks.
Overglaze: the overglaze serves to protect the gilding from ageing and to reduce the shine of burnished gold. It can be performed by applying a fine layer of wax, shellac, mecca varnish or other substances. It is not strictly necessary, but improves the maintenance of sheen over time.
Ageing: during restoration it is necessary to render the new leaf homogeneous with what remains of the original. To do this, it is brushed with a solution made of bitumen diluted in turpentine, or with a special varnish of the correct colour, taking care not to leave streaks. Once the first coat has been brushed on, the application is then rendered uniform using cotton wool.
Decoration: punches and seals can be applied to the gold leaf to decorate the articles produced.
Ammannitura or Imprimitura (priming): in modern and specialist literature this indicates the upper and finish layer of a ground preparation, characterised by a fine depth and a smooth and uniform surface, a base designed to facilitate the application of the brushwork. Depending on its characteristics, it gives the pictorial layers a transparent or matt base colouring. Traditionally the term was used in a more generic sense to signify the preparation of the painting ground using glue and gesso, and was in any case distinguished from the mestica which was characterised by the presence of oily substances.
Sponging: This ground is applied when it is desired to obtain a “soft”, delicate effect, possibly on a pastel base. It is a technique that is frequently used in combination with others.