What is called encaustic painting has also wax as a foundation, but is quite a different process to “peinture à la cire.” “Encaustic” implies burning, and in this method of painting the colors are laid on rather thick, and when the work or any portion of it has to be finished, a hot iron is applied to melt the wax and allow the brush to do its softening and finishing work.
The Pompeii paintings are mostly done in this way, but it is very unfitted for large figure-painting.
Distemper has many excellent qualities, but its want of durability will always prevent its being used for costly and important work.
It might, however, be made much more durable than it generally is, by a careful selection of materials.
Distemper is generally associated with scene-painting or some temporary work, for which any rubbish can be used; but if care were taken about the size and the colors, and above all if some coating of silica were floated over the finished painting to protect it from damp and atmospheric changes, I see no reason why this very pleasant method should not be generally used.
The so-called silica method has been much used in Germany under the name of Wasserglas. I have no experience in this method, and therefore cannot enter into detail. Speaking generally, the process consists in painting on a dry surface with colors simply ground in water, and fixing the colors afterward by the spray of silicated water. I believe that after this silication the work can be retouched and even repainted; subject, however, to another fixing by silication.
We now come to the best and grandest style of decorative work; namely, legitimate fresco. People who don’t know much about painting are very apt to call any picture on a wall a fresco, but I suppose I need hardly tell you that oil-or wax-paintings on walls are no more frescoes than is an oil sketch on paper a water-color.
In all the methods of painting I have mentioned, some medium is used to fix the color. It is either oil, copal, wax, size, or silica, but in fresco no vehicle of any kind except water is used. How then is the color fixed? How have Michael Angelo’s and even Giotto’s frescoes lasted to the present day? We all know that if some powdered color is mixed with water and applied by a brush to a wall, it will stick as long as it is wet, but as soon as the water evaporates, the color returns to the powder it was before, and falls off, or brushes off with the slightest friction. The reason that frescoes can be dusted and washed without effacing the color, is that they were originally painted on wet mortar, and the lime of which the mortar is composed has the property of retaining and fixing the color.
I will now describe the whole process of fresco-painting.
The first care ought to be the wall. A brick wall is the best, but stone will do very well, provided every precaution has been taken against damp. On this wall there ought to be a coating of strong rough mortar about half an inch thick. The surface ought not to be smoothed with the trowel, but left rather uneven. As soon as this mortar is thoroughly dry, the fresco may be begun. I have already told you that all real fresco is painted on wet mortar, but the mortar, or intonaco, as the Italians call it, is not the rough stuff which has already been used for coating the wall. The composition of this intonaco is all-important, and I am perfectly convinced that the rapid decay of our modern frescoes is due entirely to the bad quality of the intonaco.