Periodical Repainting
Page 51
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IN the September 2 issue of " The Commercial Motor" we discussed the maintenance necessary to keep paintwork in good order until such time as it becomes necessary to repaint—in many cases clue to body repairs and possibly mechanical overhaul. This periodical repainting may be at intervals of from one year to three years according to the size of the fleet and the urgency of the work on which it is engaged.
Some fleet owners find it better to stipulate repainting at definite intervals irrespective of the condition of the paintwork, and to make this painting fit in with the other reasons which justify the vehicle being off the road. Assuming that all the necessary mechanical work and body repairs have been done, the last operation in any general overhaul would be, of course, the painting.
The Existing Finish
Before the painter can decide exactly what to do, a thorough examination of the existing finish must be made,. This is necessary to ascertain whether or not the paint must be removed and the job stripped to the bare metal, or whether a good rub and re-surfacing would suffice. Points to look for in regard to paint failure are definite cracks in a large pattern similar to crocodile skin. or a minute crazing which is revealed only by the closest scrutiny.
Defects which are more easily noticed and recognized are chipped places, due to slipping screw-drivers or other means, and peeling, due usually to insufficient preparation at the time of the original painting. Should the finish show any or all of these defects, • then the decision would be to strip to bare metal. However, it should be noted that this will apply only to a cab because if the body be badly marked or blistered, then the finish may be removed with a blow lamp and a stripping tool.
Stripping is best done with the aid of a solvent-type paint remover. The procedure is quite simple, consisting merely of dabbing on a heavy coat of the paint remover to the panels, etc., leaving to soak until the paint lifts, and then using a broad knife to effect removal from the surface. What is not quite so obvious or simple is the more tedious operation of cleaning off all traces of the paint-remover and the paint residue which lurk in corners, hinges and door edges, etc. This is most essential as any paint-remover left on the surface of the metal will hinder the new paint from drying.
Surface Must be Clean The best method of ensuring this State of cleanliness is to use a stiff brush and turps, followed by abrasive paper 100.D, using in turps instead of in water. The Use of cotton waste or clean rag is essential to complete the drying off of the turps or other cleaning solvent.
After the removal of all the paint and paint-remover, the jobis ready for priming. However, before discussing the subsequent stages of the work we must see what preparation is necessary in the case of the vehicle the finish of which does not show anyof the afore• mentioned defects, but merely is in need of a good freshening up, perhaps in a different colour scheme.
The preparation in this case consists of rubbing down with 180 grade wet or dry abrasive paper, used wet, and a little sugar soap in the water to help_ eliminate traces of grease which may be present on the panels or the door edges.
During this rubbing operation care must be taken to ensure that the letter jag, which normally stands up from the panel, is rubbed entirely level, otherwise it is bound to show in an exaggerated manner through the new finish. Even where it is intended to re-letter in identical fashion, it is still necessary to rub away as it is almost impossible to position the new style over the old.
The Primer Stage
When the rubbing and cleaning are completed the work may go forward into the primer stage if this be judged necessary, e.g., if the colour is to be changed, otherwise the undercoat synthetic enamel may be brushed directly on to the old surface. .
In the Case of a stripped job the painting would follow the procedure outlined in previous articles dealing with new work and nothing further need be said. The rubbed down job will now be given its undercoat and this will be followed by a coat of halfand-half undercoat and finishing • synthetic enamel. This is to act as a surface coat and when hard-dry, usually the next day, the job must be flatted using 280 paper and soap and water.
The surfacing is now followed by a fairly heavily applied coat of the synthetic enamel and again left to -dry overnight. The next day. after flatting with 320 paper or pumice powder, the lettering, lining and other embellishment are carried out, and after the completion of all detail work, the job may he completed by varnishing with synthetic varnish, overnight drying, and final inspection.
Sometimes the painter is called upon to repaint a vehicle, the paintwork of which he has no knowledge. For example. a newly acquired used vehicle may require -repainting and there will be no indication as to when the job was painted or, what is more important, what materials were us-ed.
Using a Sealer.
Should the finish not warrant complete removal and yet cause doubt as to its soundness if used as a base for a re-finish, then the use 'of a "sealer is recommended, These sealers are best sprayed on, and therefore the procedure to be adopted when rePainting such a .vehicle will be as follows:— Rub down 'wet in the _usual -manner, mask completely for spraying,. spray on one or two coati of the sealer and. when hard-dry, proceed either with filler or, if this be unnecessary, with the undercoatsand 'so on to the finishing stages of. the work.
When repainting commercial vehicles little attention is usually given to the interior of the cab, but where time permits it should be repainted inside.