Names of pigments are not always synonymous with the colors. Dutch pink is yellow, verditer is blue, lake is not purple-blue always, but sometimes green, yellow, brown, etc., or it may be found as a pigment color, with a chalk base, or body.
Before proceeding to describe the actual method of mixing, a few general remarks on colors may be given. White lead is used for the base of paints, because that pigment possesses greater covering properties, or body, as it is technically termed, than any other. Zinc white may be used for a base under certain conditions, and color mixed with it will not be so likely to fade as when mixed with lead. The tendency of zinc white, however, to chip and crack renders the addition of lead necessary in some cases. When practicable, the natural earth pigment should be used for tinting purposes in preference to those which are manufactured. Raw umbers, raw siennas, etc., will be found to last longer than burnt umbers and burnt siennas. As a rule, burnt umber should not be used for outside painting, but the required shade should be obtained by mixing lamp black and an oxide color, such as Venetian red.
Common colors include lamp black, red lead, white lead, Venetian red, umbers, and all other common ochres, such as greys, buffs, stones, etc. Superior or ornamental colors include bright yellows, warm tints, blues, mineral greens, etc.
In compounding pigments for painting, there is yet a further matter requiring some little consideration by the painter. All blue pigments are not chemically suitable for mixture with yellows or reds, nor all yellows with reds; in fact, a knowledge of the chemical source and affinities of pigments is almost a necessity to the painter and decorator.
As the most brief and simple way of aiding the student, it will be well to mention those ordinary pigments which it is usually advisable not to mix together.
For mixing with oil color paints, chrome is an undesirable pigment, and it is particularly to be avoided when compounding greens from Prussian or Antwerp blues, which latter colors it would eventually destroy. In such an instance, for common use the best substitute for the chrome would be ' bright yellow ochre, or, as it is often called, yellow paint. Raw sienna can also be used with the above blue pigments without much detriment to either. In any case where a bright mixed green is absolutely necessary the lemon chrome can be used in conjunction with good ultramarine blue or indigo.
In compounding the secondary color of purple from blues and reds, there is less danger of trouble arising. The best and purest is obtained by mixing ultramarine with madder lake, which is a beautiful crimson and transparent permanent pigment, while lakes derived from cochineal are unstable, ultramarine and vermilion will also answer. Prussian blue and vermilion give very deep purple, which may be lighted up with white. For common purposes, the cheap purple brown is most useful, if required full in strength, but if lighter and pure tints are wanted in oil or distemper, ultramarine blue and vermilion, or, for cheapness, Venetian red, is necessary. Prussian blue in water would not suit so well, but indigo could be used if cost is not a consideration.
The remaining secondary, orange, is not a color very much called for. Orange chrome or orange red is a bright opaque pigment, but otherwise like all the chromes, not a commendable article. Burnt sienna is a very opposite pigment in both nature and source. It is semi-transparent, reliable, and permanent, and is, when of good quality, a remarkably strong stainer, like Prussian blue in this respect. In compounding orange color, the reds and ochres already mentioned are usually bright enough, yellow ochre and Venetian red, or raw and burnt sienna together, give with white lead, a good and serviceable variety of permanent orange and salmon tints.
The conrpounding of the third division of material colors, the tertiary, from either of the two secondaries, is a subject that need scarcely here be dealt with. The painter who works at this subject will soon find those secondary pigments of orange and green which produce the tertiary citrine, whether bright or sombre, such as occasion requires. Of the remaining tertiaries, russet and olive, prepared from the secondaries purple and orange, purple and green, respectively, there is a good supply in the form of simple pigments. Notwithstanding, therefore, the necessity and advantage of the painter being able to obtain any color by the admixture of the three primaries, it is always most desirable to use a simple article of the desired color when it is to be had.
In the actual mixing of paints, it must not be thought that there is any one way that is exactly right while all other methods are exactly wrong. Every painter has his own peculiar way. In nearly all cases, the simplest plan is to use pigments ground in oil instead of dry powders. With a pallet knife break up the lead rather stiff, adding a little oil. Thin down each paint until it is rather stiffer than the whole will be when ready for actual application, or if dry pigments be used, add a little oil, and thoroughly mix. The lead, zinc, or other base being ready, add some pigment, and well stir. If several pigments are required to produce the tint, be sure to add only one at a time, and take great care that each is thoroughly mixed before the next one is added. As a further precaution, it is well not to add the pigment all at once, but to do so a little at a time. When it is certain that a thorough admixture has been effected, the next pigment may be added a little at a time. It is well to remember that some pigments, such as Prussian blue, are very strong, and the addition of too much will spoil the job. It is easy to add a little more, while it is impossible to take any out.
A little precaution in this respect will save much trouble, and although it takes longer to mix the paint, it is the much safer plan. Of course, a practical painter who is used to mixing paints can add the necessary amount of colors without taking these precautions.
Having mixed the paint, add as much driers as may be necessary, taking care not to use too much. Then the paint should be strained through a fine wire strainer. It is well to mix up enough of the paint in one batch to do the whole of the job in hand, so that there may be no trouble or waste of time in matching tints. Paint mixed in cold weather is very likely to give unsatisfactory results, because the oil will stiffen and be more difficult to form into a perfect admixture. To remedy this, a gallon or so of the oil should be heated, and this poured in will warm up the paint, and prevent it pulling when applied, and so avoid the unnecessary force required to draw the brush along.
In preparing oil paint, the first question to be considered is the nature of the surface to be painted, whether of wood, stone, or metal, and to what degree it is absorbent; second to this must be remembered the conditions and position of the work, such as refer to expense, durability, and drying qualities; and lastly, to bear in mind the all-important matter of appearance and color, whether the paint is for the first or last coat.
The quantities of driers, oil, and turpentine required to bring 100 pounds of white lead to the consistency of paint is a matter that must be varied accoraing to the conditions of the work it is required for. In summer-time, 1 pound of good driers to 14 pounds of white lead is ample for out-door purposes; in winter-time, 1 in 10 would be best. The quantity of oils required would be about 1 1/2 gallons for 100 pounds of lead. The proportions of linseed oil and oil of turpentine it is advisable to use depends entirely, upon the purpose it is intended for. With reference to the question of boiled or unboiled oil, it should be remembered that both oils are glossy when applied in sufficient quantity, boiled linseed oil has more body, and is more brilliant than raw-linseed oil, raw linseed oil is lighter in color, and is not so liable to blister as boiled linseed oil, boiled linseed oil dries quicker than raw linseed oil.
To mix 1 pound of ordinary oil paint, take about 8 ounces of pigment the desired color. White lead for white, light grays, pinks, cream, etc., Venetian red or vermilion for red, and so on, according to the color desired. Add to this about 2 ounces of liquid driers, then make up to 1 pound with either linseed oil alone or oil and turpentine in equal parts. Remember, the more oil, the more driers is advisable, but never less than 1 part driers in 8 or 10 of entire bulk. If only small quantities of paint are wanted, that sold ready mixed would be cheapest and would do for ordinary inside work. A single pound could not be made cheaply, and some of the colors, bright red, for instance, could not be made at twice the retail price.
The ingredients for making about 40 pounds of best paint for indoors, tinted to a French gray color, would be 28 pounds of genuine white lead, 3 pounds of patent driers, about 1/2 gallon of raw linseed oil, and 1 quart of turpentine. Mix up the lead and driers with a broad stick to the consistency of a thick paste, using linseed oil. If all is to be tinted one color, for French gray add a little ultramarine blue and either a little Venetian red or lamp black. If a warm gray is wanted, add the red, if a cool metallic tint, add the black. The ultramarine can only be bought in powder; mix this well with a little oil before adding it to the paint, the other colors can easily be obtained ready ground in oil. For first coating on new plaster, nearly all linseed oil and a little driers may be used, very little lead. This will stop the suction of the plaster. As a rule, new plaster requires four coats to get a good surface.