Painting by Immersion and by Compressed Air: A Practical Handbook

by Arthur Seymour Jennings

The system of spraying is manufactured by the De Vilbiss Manufacturing Co., Toledo, Ohio, U.S.A., and 71, Newman Street, London, W.

The method consists, briefly, in spraying stain, shellac, varnish, or enamel, as the case may be, on the work by the means of compressed air, under a pressure varying from 30 to 80 pounds per square inch.

The necessary outfit comprises the Aeron sprayer itself—which is made in two styles and several sizes—the air compressor and receiver, an air transformer set, for regulating the pressure and purifying the air supply, a steel Fumexer, in which the work is done, and an exhaust fan to disperse the vapours or fumes resulting from the atomising of the finishing material. Besides these necessary appliances, turn-tables are used where advisable to facilitate the handling of the work while the "aeroning" is being done.

The two styles of Aerons are shown in the illustrations, each connected with an air transformer set to which the air supply pipe is attached. In one style of Aeron the finishing material is carried in a pint or quart capacity cup forming a part of the Aeron itself. The other machine takes its supply from a five-gallon container suspended above the nozzle. The work is placed in the Fumexer on the turn-table, which can be tilted at any convenient angle and revolved by hand, and is coated on the top, sides, and front, with the drawers in place. Drawers may also be finished inside by this process.

A full coat can be applied to a vertical surface as well as to one in a horizontal position. There are two reasons why. It is impossible to put on a perfectly uniform coat with a brush, especially on a vertical surface, and runs and sags are caused by the heavier portions of the coat dropping down over the lighter coated spots. With the Aeron a uniform coat of varnish is applied, and it is a fact that as the coat is the same over the entire surface it will not run, even if it is as heavy as a brush coat, which would show sags. The second reason is that an Aeron coat sets somewhat quicker than a brush coat, owing to a slight evaporation of the solvent caused by the action of the compressed air. Again, since the coat is uniform it sets uniformly. For the same reason the final drying is hastened to some degree.

In brushing flat horizontal surfaces where a heavy coat is applied it is almost impossible to avoid fatty edges, and in brushing carved or ornamental relief work the low spots are sure to collect more varnish than the high places. Corners and edges in panel work are also causes of difficulty in this respect. In using the Aeron the surface varnished is covered uniformly and evenly, whether flat, panelled or carved, with one sweep of the machine at an even speed. Consequently, heavy spots, runs and fatty edges are entirely avoided.

In applying finishes with the Aeron a slight reduction of the material with turpentine or other solvents is logical; with some materials, necessary. Reducing is logical on account of the slight evaporation of solvent previously mentioned. In other words, in order to have the Aeron application of the same consistency after reaching the surface as it is when brushed, a reduction of from 5 to 10 per cent. would be required. This is not always desirable by any means, especially in the case of the heavy gloss coat spoken of. Whenever a free-flowing coach varnish is used, reducing is not necessary. Conditions in different plants govern this matter to a great extent.

Rubbing varnishes are usually reduced slightly, as a full-bodied, heavy coat is not required, also because a rubbing varnish does not flow as readily as a coach varnish. On account of this evenness of the coat, an Aeron coat of rubbing varnish is somewhat more easily and quickly rubbed either by hand or by machine.

Undercoat varnishes are reduced to some extent for Aeron work for similar reasons. They are also more easily sanded than when brushed.

Pigments, primers or first coaters are Aeroned to better advantage if the pigment content is less than for brushing. It is also sometimes desirable and expedient to use a more finely ground pigment.