Under the head of "Paints used for Dipping" some information has been given in respect to the paints suitable for that purpose. Some, but not all, paints are suitable for both dipping and spraying, the exceptions being the heavier or more viscous compounds, which are not suitable for painting by immersion because they are too thick. Tar, enamel, and the heavier varnishes may be given as examples, although they may be successfully applied by the spraying process.
Sometimes in dealing with the heavier compounds the application of heat is an advantage. This may be applied to either the paint or the compressed air or to both in order to increase the fluidity of the compound. It is important when heat is thus applied that the temperature of the room in which the spraying is done should be raised correspondingly, so that the heavier paints, enamel, etc., do not congeal by being directed against a cold surface. Under most circumstances it is unnecessary to apply heat, provided that the spraying room is kept at a temperature of not less than 60° F. both in summer and winter.
As already intimated, the preparation of paints, lacquers and varnishes for both dipping and spraying necessitates a close study of the special requirements. In the case of paint the particles of pigment must be very finely divided as coarse material would tend to choke up the spraying apparatus, or if even they did not actually have that result they would require a greater pressure of air and thus add to the cost of working. Zinc oxide, the various grades of black and most bright reds, are examples of finely ground pigments which are well suited for spraying.
In buying materials for this purpose it is well to purchase of those firms who have made a special study of the subject. The following is a list of a few such firms, all well known to the writer, and although it by no means exhausts the list yet anyone desiring to buy materials may very safely leave themselves in their hands.
Messrs. Docker, Bros., Ltd., Birmingham; Gittings, Hills and Boothby, Ltd., Tower Varnish Works, Long Acre, Birmingham; Goodlass, Wall and Co., Ltd., Seal Street, Liverpool; A. Holden and Sons, Ltd., Bradford Street, Birmingham; Indestructible Paint Co., Ltd., King's House, King Street, London, E.C.; Lewis Berger and Sons, Ltd., Homerton, London, N.; Llewellyn Rylands, Ltd., Balsall Heath Works, Birmingham; Mander Bros., Wolverhampton; Postans and Morley Brothers, Ltd, 19, Lionel Street, Birmingham; The Frederick Crane Chemical Co., Birmingham; Thornley and Knight, Birmingham; Wilkinson, Heywood and Clark, Ltd., Caledonian Works, Poplar. E.; Pinchin, Johnson and Co., Ltd., Bevis Marks, London.
The following are American firms:—
The Moller and Schumann Co., Chicago, Ill.; John Lucas and Co., Inc, Gibbsboro', N.J.; The Chicago White Lead and Oil Co., Chicago, Ill.; John W. Masury and Son, New York, N.Y.; The Glidden Varnish Company, Cleveland, O.; The Sherwin-Williams Co., Cleveland, O.;
STOVING ENAMELS.
We now reach these important enamels, and extract the following from the foreword of the little book above mentioned. Messrs. Wilkinson, Heywood and Clark claim to be the first successful makers of stoving blacks, which was in the days before the introduction of bicycles. Though originally introduced for cycle work, stoving enamel produces a most successful finish for all kinds of materials. In the United States of America such enamels are used in great quantities for finishing standardised motor bodies. These black enamels have gained a very high name for themselves, as properly baked they are extraordinarily hard, brilliant and tough, and when applied over such material as tin sheets are flexible enough to withstand being bent double without showing signs of cracking. An important feature are the coloured enamels made by the same firm, which run through a whole series of yellows, reds, browns, greens and blues, and are hard, durable and tough, and can be stoved without changing colour. We extract the following notes on the "Application of Stoving Enamels," and fully endorse the recommendations offered:—
1. All work should be perfectly free from dirt, grease or oil, before application of enamel.