Part 2

Cennini recommends, alternately, the yolk and the white, depending upon the purpose, mixed with the juice of figs. This, evidently, must refer to the sap of the fig tree; for, it is well known that rubber is obtained from the fig tree. A slight incision in any fig or rubber plant gives a milky excrescence, which has considerable adhesive power, and which contains about half rubber and half water, in the form of an emulsion. The yolk of the egg was, however, mostly used for fresco, panel and metal.

* * * * *

Dry white of egg may be bought as a commercial article, as eggs are gathered for this purpose in large quantities in China. This may be dissolved in a weak alkaline solution, and of course this solution must be made in the cold, the alkali, if it be ammonia, being allowed to evaporate at room temperature, even after the oil is added. Otherwise, as anyone knows, the boiling of any white of egg solution, coagulates it, leaving hard boiled white of egg as the result. The ideal Tempera solution for manufacturers to use would, therefore, be Casein, to which the requisite amount of oil should be added--or, white of egg and a drying oil.

Unless a preservative be added to a Tempera emulsion, it will rot and decompose in a very short time. For this purpose there are many preservatives. Oil of Cloves has been used from the time of the Egyptians. In fact, boiling or mixing with spices has been regarded as the natural disinfectant and preservative. Modern chemistry, however, teaches us that materials like Benzoate of Soda, Salicylic Acid, Boric Acid and Carbolic Acid are the best preservatives, although if insufficient amounts are added, the Tube Colors will decompose in time. If Tempera Colors are used in the place of Water Colors for painting on paper, care must be exercised that the colors are applied very thinly; for, if the slightest attempt at impasto is tried, the colors will crack, and in many instances fall off after they have thoroughly dried out. The binder in Tempera Colors is really so weak that it will not support by gravity a large quantity of pigment. Therefore, thin painting in Tempera, especially on paper, is always essential.

The Permanent Palette for Tempera Colors is the same as that for Oil Colors. If no interaction between Tempera Colors takes place while they are in the process of drying, there can be no reaction that will ever take place after they are once dried, since dry chemicals do not react. Hence, after Tempera Colors are varnished, they may be regarded, if permanent to light, to be permanent forever. There comes, then, the question which has been mooted so often among artistic painters--Why varnish a Tempera painting at all, since the idea is to produce the flat effect?--to which the answer must be made that a painting, no matter of what it is made, unless hermetically sealed, either in a glass covered frame or with varnish, or both, is bound to be acted upon by our modern indoor atmosphere, and varnishes can be made, and are made, which dry with an absolutely Matte finish, so that these may be used with perfect success over a Tempera picture.

There are several types of Tempera Colors on the market. Strictly speaking, a Tempera Color should be a mixture of Albumen, made either of dried or fresh white of eggs, linseed oil and water beaten up into an emulsion. It is not generally known among the laity that all vegetable oils, whether they be drying or non-drying, will make an emulsion with lime water or any other alkali, but lime water is probably the best emulsifying agent to use. This medium, when mixed and ground with dry colors, forms the well-known Tempera, similar in all respects, to that used by the primitive Italians. One has only to see the remarkable permanence of the early Italian Tempera painting to conclude beyond peradventure that this medium must be regarded as one of the most permanent in existence.

There are further types of Tempera Colors on the market which contain little or no albuminous material, but which are simply mixtures of linseed oil and water. I am refraining from discussing scientifically the manufacture of emulsion paints, because that has been described fully and at great length in another publication.[4] So that, for the present, it is only necessary to say that it is a simple matter to combine oil and water for Tempera painting. There are paints on the market sold under the name of Matte Colors and Tempera Colors, which are emulsions of linseed oil and water only. But, these have neither the plasticity nor the smoothness of film, after they are dry, of the Tempera Colors which contain albumen. If the artistic painter will use only those pigments previously described which are permanent, whether they be ground in Linseed Oil or whether they be Tempera Colors, and a medium so prepared that noxious gases cannot penetrate through either side, absolutely permanent results will be obtained.

WATER COLORS

Water Colors are either put up in little cakes, in pans or in tubes. In every instance, they are ground very finely in a watery Medium to which some glutinant material has been added, such as Gum Arabic; and, in the case of tube colors and pan colors, Glycerine, sugar or Glucose, to prevent them from hardening or drying out entirely. Water Colors, excepting those of the Tempera type, which contain oil, cannot be varnished, but they are “fixed” with a solution of gum or Casein, so that they do not rub off or drop off of their own weight. There are entirely too many unstable Water Colors made. Some manufacturers carry as many as one hundred and forty different pigments in cakes, pans and tubes.

A generation ago some artists fixed their water colors by means of Gum Arabic. In some cases the gum shriveled up and became opaque. Water colors should, of course, never be varnished, but may be fixed, if necessary with a very weak casein solution.

The perfect and simple palette of Water Colors is practically the same as that of Oil Colors, with a few additions, as follows:

Zinc White. Constant White.[5] Lamp Black. Yellow Ochre. Raw Sienna. Raw Umber. Burnt Sienna. Cadmium. Burnt Umber. Indian Red. Venetian Red. Ultramarine Blue. Cobalt Blue. Chrome Green, Opaque. Chrome Green, Transparent (Emerald Oxide of Chromium). Vermilion. Madder Lake.

A Water Color painting must be hermetically sealed in the frame and it must not be backed up with a thin Veneer of wood, for time and again these wood veneers contain knots which are very resinous, and these resins, in a warm room, will evaporate, strike through and form a yellow spot or ring on the painting itself. The best way to frame or hermetically seal a water Color, in order to make it permanent, is to have a glass front and the glass should be fastened around the inner edge of the frame by means of a strip of adhesive paper to exclude air and moisture. The Water Color is then inserted and backed up with a piece of cardboard, academy-board or thin metal, such as Zinc, Aluminum, or even Sheet Iron. When this has been thoroughly fastened by means of brads or nails, the entire back of the picture is then sealed with heavy paper which has been thoroughly soaked on both sides with a good glue or starch size. In this manner a Water Color will remain permanent. A strip of wood, a quarter of an inch thick, should be inserted between glass and drawing, so as to prevent the paper from resting against the glass. Water Color pigments may be mixed with each other without danger of reaction, because, once they are dry, no further reaction will take place, as dry colors do not interact. An exception, of course, must be made in the case of Flake White and Ultramarine Blue, although Flake White as a Water Color is totally unnecessary. The question of the hiding power of Flake White as compared with other colors, will be mentioned later. But, a good coating of fixative, whether it be composed of a glue size or a Casein size, or even an alcohol varnish, is essential in the protection of Water Colors from atmospheric effects.

_Colors Which Are Absolutely Permanent Which Are Not Generally Used And Which May Be Mixed With Any Other Color Without Decomposition--Not Mentioned in the Simple Palette._

Black Lead. Graphite. Alumina. Blanc Fixe.[6] Charcoal Black. Charcoal Gray. Mineral Gray.[7] Ultramarine Ash.[8] Ultramarine Green. Ultramarine Violet. Ultramarine Red.

_Colors Which May Be Used Alone And Which Are Perfectly Permanent After They Are Varnished._

Flake White. Chrome Green--Light, Medium and Dark.[9] Chrome Yellow--Light, Medium and Orange. Prussian Blue. Emerald Green.[10] Antwerp Blue. Naples Yellow. Orpiment. Chrome Red. Indian Lake. Genuine Alizarin Lakes of all shades. Burnt Umber. Madder Lakes of all shades. Chromate of Barium.[11] Chromate of Zinc.[12] Chromate of Strontium,[13] (sometimes called ultramarine yellow).

PERMANENT FOUNDATIONS FOR PAINTING

Many a painting decomposes, cracks, chips and otherwise fails, because the foundation upon which it is painted is unstable. There is an enduring feature connected with oil paintings which has been described elsewhere[14] and it is not necessary to go into this subject in this volume; but, suffice it to say, that canvas is the least permanent of all foundations, and there is hardly any one of the paintings by the Old Masters, or even any of the paintings in existence by the Modern Masters of one hundred years ago, that has not been relined; that is to say, the canvas has been mounted on other canvas in order to give it stability and permanence. The principal foundations that have been used have been wood of various types, and metal. Wood really is as permanent as anything in existence, excepting that eventually it becomes either rotted, through excessive moisture, or a certain worm invades it and bores irregular holes through it. The most permanent of all foundations is metal. The Dutch have painted on copper, and where the copper has been rather smooth the paint has eventually curled or peeled. Sheets of Zinc or sheets of Aluminum are regarded to-day as the most permanent foundations for all paintings up to a certain size, but beyond a certain size canvas must necessarily be used. I have always advocated the painting of canvas on the reverse side, to prevent noxious gases from working their way through to the under side of the painting, and the painting of the reverse side of canvas is not as simple as it may seem. In the first place, if a painting is to be protected by painting the reverse side of the canvas, after the painting has been completed, unequal tension takes place and the painting buckles, so it is necessary under all circumstances to remove the canvas from the stretcher and re-stretch it. Then again, Linseed Oil paint must not be used either on cotton or linen direct. Linseed Oil is acid, and eventually rots or decomposes all vegetable fibre. It is for that reason that canvas is always first prepared with a glue solution, which is neutral and prevents the soaking in of the oil paint, so that if the reverse side of the canvas is to be painted, it must be either coated with a glue solution, or, what is equally good, it must receive a thin coating of Shellac Varnish. Glue solutions are made by using a double boiler, such as carpenters use, or such as housewives use for boiling rice or other cereals. A pound of glue or gelatine is soaked overnight in a quart of cold water. This swells the glue and makes it ready for boiling. Then it is placed over the fire in a double boiler and more water added, until it has the consistency of very thin cream. After it has been allowed to cool, it is applied to the canvas. Then, after that, any good mixed oil paint may be applied. I have, however, always recommended a mixture of such pigments which shall neither dry too hard nor too soft and will not eventually become too brittle. For this purpose, the following pigments may be mixed and may be obtained from any reputable dealer in house paints:

One pound of Red Lead in Oil. One pound of Zinc White in Oil. One pound of Pure White Lead in Oil.

mixed with one-half pint of Turpentine, to which one-half pint of raw Linseed Oil is added. This makes a salmon-colored ready mixed paint which dries slowly, evenly and is very impervious, and if the color is at all objectionable and too light, Lamp Black may be added to produce a Chocolate Brown. The Lamp Black should be added in oil without the addition of any further varnish or drier. But this must, of course, be applied over the glue size heretofore mentioned, and at the end of a week the painting can be restretched and will show no corrugations or buckling.

In spite of wood being a more durable painting material than canvas, artists prefer canvas, simply on account of the difference in surface; for, the twill of the canvas gives the pigment an unevenness which causes it to reflect and refract light, much to the advantage of the painting.

Gilbert Stuart, in later life, painted many portraits on panels that were grooved to give the impression of canvas, and he had the surface for many of his panels prepared in such a way as to imitate the weave to which he was most accustomed.

PREPARATION OF WOOD AS A FOUNDATION FOR PAINTINGS

Mahogany wood, since the Twelfth Century, has been a great favorite with painters, but an Oak panel is just as good. It is absolutely necessary, however, to reinforce the reverse side of a wood panel, either by means of a cradle or by means of cleats.

Cleats are very dangerous. Pictures split and buckle alongside of cleats, and when such buckling takes place, the picture ought to be taken off and cradled.

If the wood panel is sufficiently heavy, these cleats may be screwed on, but at all events they should be glued on with a proper glue, such as can be purchased in the United States under the name of LePage’s Glue, or Russia Cement; but, in any event, it is quite important, in addition to gluing these strips, to fasten them by means of fine wire nails which may go through to the outer surface, and then be cut off and sandpapered to a smooth finish. A very good preparation of a wood foundation is to fill the wood first with what is known as wood filler. This is a material called Silex, or Silica, mixed in a quick drying varnish. It is thinned down with Spirits of Turpentine, applied across the grain of the wood panel, and after ten or fifteen minutes it is rubbed off lightly, the fine grain of the wood becomes filled up with this Silica or wood filler; and, after twenty-four or forty-eight hours, the surface is then rubbed with very fine sandpaper, which makes it perfectly smooth. Then a thin application of Shellac Varnish is applied; and Shellac Varnish for this purpose is manufactured by taking two pounds of any Orange Shellac to three-quarters of a gallon of Denatured Alcohol. This should not be mixed in a metal container, but should be mixed in a stone jar or glass bottle. In a few hours it will have dissolved, if shaken occasionally. A coat of this is applied to the wood after the fill has become thoroughly dry. Three hours afterwards it should again be lightly sandpapered. After this another coat of Shellac Varnish is applied, both to the front and the back of the wood panel. Three hours after that, it can again be lightly sandpapered, and then it is ready for painting. The sandpaper is essential because it roughens the surface and forms a bond between the pigment and the wood. If you paint on a highly polished surface, whether it be glass, metal, wood or canvas, there is very little bond between two glossy coats, and the chances of peeling are very great; but, if you roughen the surface upon which you are going to paint, there is a contact between the paint and the surface, due to the roughness just mentioned.

Shellac used in priming wood is essential, in order to prevent the resinous matter from evaporating into the painting. But, if a painting should crack, which has been based on Shellac, and a restorer applied alcohol, it is quite obvious that the painting would become badly damaged.

PAINTING ON METAL

Any metal which has rigidity, such as Copper, Zinc and Aluminum, is good to paint on and is absolutely permanent. Aluminum is the lightest of all the metals and not very expensive. It is readily purchased in any size up to 30″ x 36″ and in any reasonable thickness. The bodies of nearly all good automobiles are made of Aluminum, and when the surface is properly prepared, it holds the paint perfectly and permanently. It can be bought with a so-called egg-shell finish, but it is always advisable, before painting, to rub it very thoroughly with coarse sandpaper or emery cloth. This produces very fine ridges, which hold the paint, and that is the only preparation that Aluminum needs for permanent painting. Copper, Brass, Tin-Plate and Zinc must all be prepared in the same manner by rubbing them very thoroughly with coarse sandpaper or emery cloth, and no further preparation is necessary.

OILS AND MEDIUMS

There are on sale a very large number of Mediums for use in oil painting, some of which are essential, but most of which are unnecessary; and, for certain purposes, unreliable. The materials generally on sale--and this is not a complete list--are:

Poppy Oil. Linseed Oil. Walnut Oil. Nut Oil. Pale Drying Oil. Dark Drying Oil. Spirits of Turpentine. Petroleum Naphtha. Amber Varnish. Copal Varnish. Japan Oil Size. Mastic Varnish. Megilp Varnish. Damar Varnish.

and other materials, the compositions of many of which are kept a secret and are sold under proprietary names. As a matter of fact, the painter can get along perfectly, and will have permanent results, if he sticks to Raw Linseed Oil, Turpentine and one Varnish, either Mastic or Damar. I do not mean to say that a Medium like Copal Varnish mixed with certain colors is not a good Medium, for such a material will produce enamel paints which will have a permanent gloss, but when you come to consider that the Old Masters had only from seven to ten pigments ground in a drying oil like Linseed Oil, and that most of their paintings are to-day a complete example of permanence, there should be no reason why the mind of the painter should be clouded with a multiplicity of materials and why many materials should be used which may in time prove detrimental.

Without going into any scientific dissertation on the subject, if you take a strong drier and mix it with many pigments like Umber, Zinc and the Siennas, you will have, apparently, a perfectly dry picture in twelve hours, but you must bear in mind that the drying process, once started with these powerful driers, goes on sometimes for years, until finally the paint disintegrates, because too much drier has been used. It is, of course, oftentimes essential to use plenty of drier, or to use Copal Varnish as a Medium, in order to finish the work so that it can be handled with safety for illustrative uses, but where a painter has a commission to paint a portrait, it its far wiser to use the simple palette and to reduce only with Turpentine and Raw Linseed Oil and let the sun and air dry his picture slowly, normally and naturally.

VARNISHES

No picture should be varnished before it is at least six months old, for I have already stated that the process of drying with Linseed Oil Colors is progressive, and keeps on for years, and if a picture be varnished too soon, cracks are bound to result. Only those types of varnishes should be used which can be readily removed and the three types that can be readily removed are Sandarac, Mastic and Damar.

Sandarac is a varnish which dissolves in Alcohol and dries perfectly within three hours.

Mastic is a pale gum which dissolves only in Turpentine and dries hard and dust-free overnight.

Damar is similar in its characteristics to Mastic, but not quite as hard.

Pictures with a heavy impasto, and particularly those in which the slow drying pigments are used, should not be varnished inside of a year--or, preferably, in two or three years. All Linseed Oil and Poppy Oil paints dry from the surface down and wrinkle like a desiccated apple. If a curved needle is inserted into these wrinkles, it is very often found that the interior is still liquid or semi-liquid. I have found globules of graphite and lamp black mixed with Linseed Oil, to remain soft after many years. When a picture becomes thoroughly hard and it has dried completely, the film becomes as tough as a sheet of glue, and it cannot be punctured. It is then called “needle-proof.” A clot of Raw Sienna in a picture by Josef Israels ten years old was not yet “needle-proof.”

It would therefore appear that the best time to varnish a picture is after it has hardened up uniformly and completely, even though this takes a year or two.

Mastic is very largely used, but has the one great defect that you never know whether it is going to dry with a gloss or whether it is going to dry flat, and sometimes a picture varnished with Mastic will be partially glossy and partly matte. To overcome this, a small amount, not exceeding 10%, of Lavender Oil or Linseed Oil may be added.

On a bright, clear day, Damar Varnish usually dries with a gloss, but on a damp day, when the picture is moist, Damar will also dry flat.

Sandarac Varnish may be very easily removed with Alcohol, and both Damar and Mastic may be easily removed with Turpentine or a mixture of Turpentine and Benzine (Petroleum Naphtha).

For the restoration and renovation of paintings, it will at once be seen that a varnish that can be easily removed is by far preferable to the Copal Oil Varnishes, and Amber Varnishes which dry with a hard, tough insoluble film, and it is at times impossible to remove these; and, where strong solvents or much attrition is used, it sometimes happens that the surface glazing or delicate tints are removed at the same time.

The pigments that are only permanent when used alone and remain permanent after having been varnished, are:

Flake White. Chrome Green.[15] Chrome Yellow. Prussian Blue. Emerald Green. Naples Yellow. Chrome Red. Verdigris. Harrison Red.[16]