Tinted paints possess greater hiding power than white paints, and the above proportions would be somewhat changed for a tinted paint containing any percentage of coloring material. Tinted paints are, moreover, far more serviceable than white paints, as will be shown later.
Mill vs. Paddle: The mixtures under consideration should be ground in linseed oil by the manufacturer, through stone or steel mills, to a very fine condition, as it is only through proper grinding that the pigments can be properly blended. The mixing of paint by hand is, fortunately, to a large extent a thing of the past. The uneven lumping of hand-mixed paints are often the cause of their failure. Such ancient and crude practice should be avoided by every painter, for it is more economical to obtain semi-paste paints, properly ground by machinery, to such a condition that they may be easily broken up and tempered. Such paints may be reduced to the proper consistency with oil and volatile thinner for application to any kind of wood.
In the opinion of the writers, a majority of the paints sold by reputable dealers and made by reputable manufacturers in this country are not only made from the best linseed oil and highest-grade pigments obtainable, but are put up in a form ready for the painter to thin down with full oil or turpentine reductions, either for priming work or to be used without reductions for finishing coats. The large metropolitan painter who wishes to make his own tints and shades may, however, prefer to have his mixed pigment paint ground by the manufacturer in heavy paste form for certain purposes.
Results of Field Tests: A careful analysis of the results of field tests which have been carried on in different parts of the country would be far too voluminous for insertion in this bulletin. The official findings of special committees of inspection have already been published in special reports. Whereas there may still remain ground for some difference of opinion in regard to the interpretation of the results obtained on the various test fences, there can be no doubt that considerable information of the highest value has been yielded, both to the producers and consumers of paints. One of the principal results obtained from these tests has led to the opinion expressed above by the writers, that better results can be obtained by a proper mixture of selected pigments than by the use of any one pigment in linseed oil. This conclusion has also been reached by engineers of the United States Navy, and, as a result, the specifications of the Bureau of Yards and Docks for paints made of straight white lead and oil have recently been changed to call for white lead combined with upwards of 50 per cent of zinc oxide. Many engineers and master painters have interpreted the results of the tests in the same way, and the attention of the authors has been called to a number of opinions which show that the tendency of demand among those who are properly informed is for a high-grade combination type of paint rather than for any single pigment paint.
Color: The selection of the color for a dwelling or other structure is a matter that depends largely upon the good judgment and taste of the owner, combined with the advice of the painter. One point, however, should be impressed upon the mind of both, namely, that PRACTICALLY ALL SHADES OR TINTS MADE UPON A GOOD WHITE PAINT BASE, THROUGH THE USE OF PERMANENT TINTING COLORS, WILL BETTER WITHSTAND EXPOSURE TO THE ATMOSPHERE THAN THE WHITE BASE USED ALONE. Owing to the cheerful effect produced by the use of white paint on dwellings, a very large quantity of white will continue to be used. If these white paints are designed in line with the suggestions brought out above—that is to say, if the white lead bases are properly reinforced with zinc oxide and other pigmentary materials—better results will undoubtedly be obtained, as far as appearance and durability is concerned, than if white lead had been used alone. The consumer should remember, however, that more durable results will be obtained by the use of tinted paints.
Reductions and Thinners: Turpentine, with its sweet odor, high solvent action, and wonderful oxidizing value, has always taken first place among the volatile liquids used for thinning paints. Wood turpentines, produced from the steam distillation of fine-cut fat pinewood or from the destructive distillation of stumpage and sawdust, have been refined in some cases, by elimination of odor and toxic effects, to such purity that they are equally as good as the purest grades of gum turpentine, and their use is bound to increase in the paint industry.
The painter and manufacturer have come to understand that certain grades of asphaltum and paraffine distillates are equally as satisfactory as turpentine for use in paints for exterior purposes. Those volatile oils which are distilled from crude oil with either a paraffine or asphaltum base and possessed of boiling point, flash point, color, and evaporative value approximating similar constants of turpentine, are excellently suited to partly, and in some cases wholly, replace turpentine in exterior paints. A little additional drier added to paints thinned with these materials will cause oxidation to take place in the proper time.
Prominent master painters[A] have shown that benzol, a product obtained from the distillation of coal tar, differing from benzine, a product obtained from the distillation of petroleum, is a valuable thinner to use in the reduction of paints for the priming of resinous lumber such as cypress and yellow pitch pine. The penetrating and solvent value of benzol is high, and it often furnishes a unison between paint and wood that is a prime foundation to subsequent coatings, preventing the usual scaling and sap exudations, which often appear on a painted surface. Because of the great solvent action of benzol, however, this material should never be used in the second and third coatings. These facts will doubtless interest the Southern painter, who has so much wood of a refractory nature to paint.
[A] Dewar, Titzel et al.