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Finishing Commercial Bodywork
Page 146
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Developments in Synthetic and Other Paints Which Give Durability and Good Appearance, and a Summary of Their Individual Properties
THE proper protection and decoration of commercial vehicles present a special problem. Finishes should be petrol-proof, almost non-inflammable and proof against strain. The methods of building commercial bodies and the conditions under which they are finished are such that it is not often possible to make use of the newest developments with advantage. Cellulose, for instance, remains unrivalled as a lasting finish when applied to comparatively rigid metal surfaces, and an entirely satisfactory result can be obtained on wood under similar circumstances.
Difficulties began to be encountered when cellulose was applied to bodies built partly of wood and partly of metal. It was found that movement, due to vibration and flexing, between wood and metal' parts caused cellulose films to crack at the joints, or at the moulding covering them. The extra durability and service obtained from cellulose may justify additional trouble necessary to obtain the result, but this limits its use.
The New Synthetic Materials.
Credit is due to the paint industry, for it immediately appreciated that cellulose was not the answer to the commercial vehicle finishing problem. The limitations of cellulose and the oil-paint and varnish process made it necessary to find new materials if any advance was to be made, and there is evidence to show that the new synthetic materials fulfil all the demands of the coachpainter. Finishes based on synthetic resins have accomplished what cellulose previously failed to do.
Synthetic finishes are made from manufactured, not natural, resins, and it is possible to control the product by chemical means, so that durability, flexibility and hardnesg may be enhanced or diminished as desired. Control is Possible with only the true synthetic finishes, and does not apply to some described as " synthetic " but actually containing only a small quantity of synthetic material, often a little brittle synthetic resin.
A notable example of the new finishes is Dulux, manufactured by Nobel Chemical Finishes, Ltd. This has been on the market sufficiently long to enable people to judge its merits. Examination of buses and vans finished two years ago, and in service ever since, shows the finish to be in exceptionally fine condition, and to have retained all its original freshness. No signs of deterioration are evident either on the bonnet (where a varnish finish quickly fails owing to heat) or around the Petrol cap, where discoloration ;might be expected. Closer inspection shows that the finish has retained its flexibility and adhesion, From the practical painter's point of view, there are no difficulties to be en countered in applying the finishes. B16 They may be sprayed or will brush out easily and have god flow. It should be noted that no coat of varnish is required, as the finish dries with an excellent gloss.
The finishes are suitable for wood or metal, and the processes show a considerable saving in labour costs, over the older paint-and-varnish methods. The resulting finish is equal in appearance to a varnish finish, and has the durability of a first-class cellulose applied to a rigid, metal surface.
Amongst other excellent materials is Bripal commercial body finish, which gives a hard, smooth, non-porous surface showing a high gloss, which is par
ticularly easy to keep clean. It is neither an ordinary enamel nor a cellulose material, but has as its base synthetic resins, and it may be of interest to mention that The Motor'van, which is such a familiar sight at motoring events throughout the country, has just been finished in this material.
No stoving is required, as the finish dries rapidly and is not readily attacked by oil, grease, petrol, etc. It is supplied for application either by brushing or spraying. Booklets describing the material and its application are obtainable from Brown Bros., Ltd., Great Eastern Street, London, E.C.2.
Thos. Parsons and Sons, Ltd., 315 and 317, Oxford Street, London, W.1, has produced a new type of enamel for brush application which gives a finish similar to cellulose, but does not require polishing. It is known as Parsonol.
It is made on a synthetic-resin base, and does not set too quickly, giving ample time for brushing, whilst it flows out well, dries in about six to seven hours, and gives a surface which does not crack or chip.
Another finish particularly suitable for commercial uses is Nova; produced
by The Walpamur Co.' Ltd., 35-36, Rathbone Place, Oxford, Street, London, W.1. This combines the quick. drying properties of a new oil made under a patented process, with the resistance and other valuable characteristics of a synthetic resin.
The initial period of contact with air, necessary for the drying of ordinary paints and enamels, is practically eliminated. The coats dry by setting uniformly throughout, rather than from the surface downwards, thus producing an extremely tough film with aporcelainlike surface. It can be either brushed or sprayed.
Where the vehicle is required to be particularly smart; two coats Of the glossy finish can be applied, the second being applied after the first has been rubbed down.
Finally, there are two products of considerable use to those who wish to touch up damaged surfaces, or even to achieve a complete repaint in the case of the owner-driver. One of these is Motor Ripolin, the product of Ripolin, Ltd., 8-9, Drury Lane, London, W.C.2. The first coat dries with a dull surface, whilst the second gives a high gloss, no varnish or other transparent coat being required. Another grade, known as Ripolin Speed Enamel, is recommended where a preparation having quick drying characteristics is essential.
A Touching-up Outfit.
The second product in this class is supplied complete with a special spraying device mounted on the tin, and this can be connected to a foot, band or power-operated tyre pump, thus enabling wings, panels, etc., to be touched up easily and rapidly. The material employed is called Celamel and is supplied by Postans, Morley Brothers and Birtles, Ltd., Trevor Street Works, Birmingham, 7.
In this case, the finish is a cellulose lacquer, which is quick drying and thinned ready for spraying. It can be used satisfactorily over other cellulose, old hard enamel or paint, or stoved enamel.