It might appear that it is unimportant when varnish is applied so long as the work is inside, and is not exposed to showers of rain. As a matter of fact, varnish is the most susceptible material used in painting, and the better quality it is the more sensitive is its nature. In hundreds of cases of varnish which turned out badly, it is safe to say that in nine cases out of ten the trouble is to be attributed simply to the state of the weather. If varnish is applied on a foggy day, for instance, it is almost certain to bloom, that is, a dull appearance almost like the bloom on fruit will appear on the surface. This is difficult to get rid of, although a rag dipped in kerosene oil passed over the surface will often assist. It sometimes happens that a day may be free from rain, and yet a very bad one to do varnishing because the atmosphere may be charged with humidity. A dry day and a warm one is the best for applying varnish. Still, there are other considerations which should not be overlooked. A hall which was varnished showed on one side very badly, while the other side was apparently perfect, the same varnish being used by the same workman.

Such a case appears to be somewhat mysterious, the explanation of such cases is probably that the weather was cold, that the door was open during the process of varnishing, which chilled that portion of the surface reached by the cold air.

Varnish manufacturers who understand quite well the nature of their products take care to mature their varnishes by storing them in tanks for months together, and in all well-regulated varnish factories the temperature of the maturing room is kept uniform the year round, for unless this is done the products would vary greatly in use, and give a great deal of dissatisfaction. It will be seen from this that in putting varnish aside it is necessary to store it in a warm place, and to take care that it does not get chilled, if it should become very cold it is well to gently heat it before using it. In piano factories, carriage shops, and in any other places where the varnished surface must be very brilliant and uniform, it is often the custom to take the most painstaking care to prevent any marring of the varnish by cold, draughts, or dust. The temperature is kept always uniform by means of steam or hot air pipes, double doors and windows are used, and sometimes the precautions taken go to the extent that all the air entering the room is thoroughly strained and freed from dust. The workmen have clothes which they put on previous to entering the room.

It is not suggested that painters should take any precautions of this kind, but mention is made of the subject here in order to impress them with the necessity of taking the greatest care with varnishing.

There are two additional reasons which give rise to unsatisfactory varnishing. The first is the habit of mixing varnishes. Experienced painters will sometimes assert that they can get a better result by mixing two varnishes together than they could by using only one. There is some excuse for the practice when the supply of a certain varnish runs out, but ordinarily it is entirely against common sense. Varnishes are made for so great a variety of purposes that there is no necessity to mix two together. A moment's reasoning will make it clear that if two varnishes mixed together would give a better result than either one used separately, that the varnish manufacturers themselves would make such a mixture before sending the varnish out. It is quite possible that the ingredients from which the varnish are made would react detrimentally one on the other. It is therefore strongly advisable for the painter not to mix varnishes under any circumstances.

The second objectionable practice alluded to is that of thinning the varnish by adding linseed oil to it; in cold weather varnish sometimes pulls, that is, it is so thick that it is a little difficult to apply without considerable strain on the wrist. In such cases the workman will sometimes add the oil, which may not show up at the time, but it is sure to eventually prove disastrous. Cases have been known where the painter, to save himself trouble, has smuggled in a small bottle of linseed oil, and has added it surreptitiously to the varnish, and caused a great deal of complaint to the manufacturers. In the above remarks only turpentine and oil varnishes have been referred to, not spirit varnish. This, however, is almost invariably mixed with stain as far as the painter's use is concerned. Under the head of Staining will be found information on this subject.

Varnishing can only be properly done by means of brushes specially made for the purpose. There is a very useful grade of varnish made which is known as rubbing varnish. This is applied in the ordinary way, and is, when dry, rubbed down with felt and water dipped in powdered pumice stone. Several coats are usually given, each being rubbed down.