Spraying Colour Specimens.
Specimens of various colours in distemper, oil, varnish and enamel are sent out in very large quantities by the various manufacturers of those goods, and the preparation of these specimens may be very considerably facilitated by using a suitable spraying machine. When distemper is used fairly large sheets of paper are usually employed, and these are cut up by means of a guillotine machine when dry. Ordinary oil paint and varnish paints may in like manner be sprayed, but when an enamel finish is desired it is usual to apply the paint on the back of a sheet of thin white celluloid, which gives the appearance which would be obtained by the application of varnish. In spraying celluloid sheets it will be found that after a little practice the paint may be laid on much more uniformly than is possible by means of a brush. This can easily be demonstrated by holding up the painted sheet to the light, when it will be found that the paint applied by a brush shows more inequalities or streaks than that when sprayed.
Stencilling may be done very well on either paper or celluloid sheets; in the case of these specimens, for example, supposing it was desired that each specimen of colour when cut up should bear a number, it would not be difficult to cut a stencil in zinc or leadfoil, repeating the number as many times as there are specimens to be cut out of each sheet. The tinfoil would then be fixed in position and the spraying done over it, which would mark each piece with a number. Then the coat of colour can be sprayed all over the surface. The plan above would be followed in the case of celluloid, but when ordinary paper is used the process would, of course, have to be reversed and the number put on last.
In some cases where a very great brilliancy of colour is required, this is done by the process of glazing, which is described elsewhere in this book; for example, a comparatively dull red could be very much brightened by spraying a coat of madder or crimson lake. Here, again, if celluloid is used the glazing colour will go on first and the ground colour afterwards, but in ordinary circumstances the ground work would, of course, be first applied.
Probably the most complete plant for preparing colour specimens is in use by Mander Brothers, the well-known paint, varnish and colour manufacturers, of Wolverhampton. The spraying of colours is mostly done on celluloid sheets, and four cabinets of the Airostyle type are in more or less constant use. These cabinets have glass sides and top hung on hinges so that they may be opened when desired. The pressure of air is usually from 30 to 35 lbs., with an additional 5 lbs. on the paint pot. One coat is sufficient, because, of course, it can be made as thick as may be necessary according to the particular specimens being prepared. The saving of time is estimated at, at least, 33 per cent.
In dealing with celluloid sheets it is obviously of importance to adopt some safe means of storing them while drying. Formerly Messrs. Mander Brothers had a long series of double clips by which the sheets were suspended while drying, but this method has been abandoned owing to the danger involved of fire. Now suitable tin-lined cabinets are provided having from top to bottom a series of cleats which support open wire trays. Each sheet of celluloid as it is painted is placed on a wire tray which is slipped in the cabinet, where it dries in 12 hours.
Tramcars.
Fig. 95.—General View of Airostyle Plant for 16 Operators on Small Work.
