A paint which dries with a gloss is often desired for the finish of many articles, and can be readily obtained by first priming, then giving a finishing coat of paint on it which has been mixed with sufficient varnish to produce the desired gloss. In some cases three coats may be given, namely, the first or priming coat, the second, which should be flat, or semi-flat, and the third a coat of varnish paint, which will dry with a gloss. It should be pointed out, however, that the finish obtained by these means is not a little inferior to that which may be produced by using over the priming one or more coats of flat paint of the desired colour and finishing with a coat of suitable varnish, which may be applied either by dipping or spraying, according to circumstances. A point here worthy of mention is one which every house painter is or should be well acquainted with, and that is that the coats of paint that are superimposed should be alternatively flat, i.e., without gloss, and glossy, in order that each may adhere closely to the other. If the article to be painted is wood or any other material which is of an absorbent character, a comparatively large amount of turpentine and oil must be mixed with it in order to allow for suction. This will dry with a semi-flat finish, and a glossy coat or one having more oil in its composition, may be applied over it. If a further coat is required it should be flat or nearly so, and in that case a finishing coat of varnish will probably be required. The paints for these purposes may be purchased ready made or ready for thinning down, from firms who have made a special study of the requirements.
The question sometimes arises as to whether paint dipping or spraying can be used advantageously when in the finish two or more colours are to be used. As a rule the difficulties can be overcome by dipping first or even the second coat, spraying on the third or finishing coat, using specially prepared masks or shields over those parts which are not to be painted with the particular colour in use.
The following useful information is taken from "White Paints and Painting Materials," by W. G. Scott, who was for sixteen years connected as paint expert with the Milwaukee Harvester Company and the J. I. Case Threshing Machinery Co. Mr. Scott therefore speaks from a wide experience. He says:—
A certain amount of oil must be present in dipping paints to act as a binder, and it is advisable to add a small quantity of varnish to hold the paint together. The desired features in a good dipping paint are: freedom of flow and proper drip; sufficient binder to prevent chalkiness and produce a firm coat; covering capacity and an even distribution of the paint.
Non-absorbent surfaces like metal and hard wood require less oil than the absorbent soft woods.
In the former case there is little or no penetration of the liquid portion of the paint, but with pine, bass wood, white wood, poplar, etc., nearly all of the liquid is absorbed or taken up by the wood, consequently with benzine only as a thinner there will not be sufficient binder present to hold the pigment when the thinner evaporates.
Whereas 5 lbs. of paste pigment or colour ground in oil and thinned with a gallon of benzine would produce a suitable primer on iron or other non-absorbent material, it would not answer for soft wood.
Dipping paints, as a rule, contain from 4 to 10 lbs. of paste per gallon of thinner, the primer containing less paste than the second coat paints.
The composition of the paste colour has much to do with the dipping paint; for instance, 5 lbs. of paste white lead to the gallon of thinner will cover and work better than a mixture consisting of half white lead and the other half made up of transparent pigments like china clay, barytes, etc., nevertheless a small amount of inert material is generally understood to be an improvement in the way of durability.
Asbestine, whiting, silica and china clay are the inert materials most often used in paste goods for dipping purposes.