There are other pigments that might be used, but are really not necessary, and some of them are doubtful as to their permanence. One colour, not in our list, is the genuine ultramarine, a splendid blue, and thoroughly permanent in buon-fresco, but its great price prohibits its use, except in very small quantities, or on small portions of the work. French, or factitious, ultramarine is also very permanent, and withstands the action of the lime, but at the same time it is a most harsh and disagreeable colour when used in lime or in any other kind of fresco; when used alone it destroys by its intensity of hue the proper values of other colours in the scheme; on the other hand, if any attempt is made to tone it down by mixing it with another pigment, or by glazing another colour over it, the result is cold and muddy in the extreme, so it is best left out of the list, as it is almost unmanageable in fresco. Vermilion is rendered durable in fresco by pouring lime-water over the powdered colour, and then draining this water off, without disturbing the colour. This washing is repeated four or five times, before the vermilion is ready for use. Permanent white, which is a barium sulphate, and tin white, or tin binoxide, may both be used in lime frescoes, but they are unnecessary, and not so good for the purpose as lime white. Lemon yellow, Naples yellow, aureolin, Venetian red, and terre-verte may be used with lime, but it all depends on the manufacture of these colours as to whether or not they may be used with safety. For example, the Naples yellow, Venetian red, and terre-verte pigments of to-day are quite different in their chemical constituents to the same named colours of the fourteenth and fifteenth centuries. Yellow ochre, though it has been used very much by the old Italian frescanti, is not to be depended upon when used in lime fresco in this country, as it consists of a mixture or combination of hydrate of iron and clay; it therefore attracts the damp that is nearly always present in our atmosphere. Of course, it can be safely used in very dry climates, but it may be mentioned that it has been one of the pigments which has largely perished in some of the frescos of the Houses of Parliament. Another objection to its use in fresco is, that the caustic nature of the lime is apt to change yellow ochre to a light red, an after effect which may not be altogether desirable. Raw sienna, however, more than takes the place of yellow ochre, and is one of the most useful colours in fresco painting. We should say that the three most permanent and beautiful colours for use on the lime plaster are raw sienna, burnt umber, and Indian red, and whether used in transparent washes or in solid tints, as when mixed with lime-white, or in the full strength of their hues, they always dry out luminous and brilliant. All the colours should be ground very finely in water, and kept in covered jars or wide-mouthed glass bottles. The lime-white should be strained through muslin and kept covered. A bone or ivory palette knife must be used, and the palette should be made of tinned metal, having a series of small circular wells to hold the various colours. Brushes are of the ordinary kind, hog-hair, and a few long sable riggers. Hog-hair brushes are best for use when they are of a flat shape, but of a roundish finish at the end, like an old or half-worn brush, so that when in use they will not disturb the surface of the wet plaster, which a new or square-ended brush is apt to do.
When everything is in readiness to commence work, a portion of the rough wall surface should be thoroughly saturated with water, and the plaster ground, or intonaco, should be laid on with a wooden trowel, beginning at the top and at an angle of the wall, and large enough in area to constitute a day’s work, or, rather, as much as can be done in about five hours; for after that time it is not safe to work on the new plaster, as it then becomes too dry: if allowed to get in this condition the colours will not properly incorporate with the body of the plaster, for if any painting is done when the plaster is in a half-dry state the colours will not adhere permanently to the wall, but will scale off the surface, or may be brushed off loosely when dry. When any portion of the plaster ground becomes too dry to work upon.
it must be cut right away and a new coating of plaster applied; it is of no avail to syringe it with water in order to keep it damp for painting on, as the water only weakens the nature of the lime in the plaster. The chemical action between the atmosphere and the lime, necessary for the firm locking up of the colours, will have taken place after four or five hours’ time, according to condition of the atmosphere; and this action will not repeat itself or be brought about by any application of water after the period named.
When the day’s work is finished, any part of the surface not painted on must be cut away, and the plaster all around the edge must be under-cut, the cut sloping well inwards, so as to form a key for the new piece of plaster for the next day’s work. This coating of plaster should be rather more than half-an-inch in thickness, and should be finished to a level, but not too smooth, a surface, with the wooden trowel, or “float.” An iron trowel must not be used. After the plaster is laid on it should remain about ten minutes or so before painting, so as to allow it to set. It should then be coated with a tint, that would be a deep vellum colour when dry, made of a mixture of lime-white and a little raw sienna, about the thickness of cream; this will give a slightly smoother surface to the plaster and will act as a luminous ground for the subsequent colouring, besides acting a very important part as an under-coating on which the superimposed colours will “bear out” more effectively. The water used should be distilled or boiled, or rain water collected in clean vessels, as hard water generally contains a quantity of chalk, and for this reason it is not so powerful a solvent of the lime as soft or distilled water.
The portion of the design selected for the day’s painting is traced from the cartoon, and is transferred to the soft plaster through the holes, which are pricked through the tracing paper, by means of pouncing with powdered charcoal contained in a muslin bag, or it may have the outline traced through with a sharp-pointed wooden stile; this will leave a slightly depressed line on the soft plaster, and is a cleaner method than the charcoal pounce, and on the whole the more preferable one.
We have now arrived at the stage of the work when the painting may be proceeded with. It may be here mentioned that, in order to try the hues of the colours and various tints, an ordinary brick having a thick coating of plaster of Paris, that has been allowed to become thoroughly dry, should be at hand. If a touch from the brush, dipped in any tint, be put on this plastered brick it will dry immediately, and show at once the actual shade of colour that such a tint will be when, after some days, it has dried out on the plaster surface. It generally takes three or four days, according to the season of the year, or heat of the room, before the wall surface and the applied colours finally dry out, and all