the paint­ing process

Total 911 - - History Of Paint To Sample -

What­ever its pig­ment, paint to­day is al­ways ap­plied in the same way and com­prises a filler-based to­tal­coat­ing sys­tem with a two-com­po­nent clear coat. Un­less ‘wraps’ are in­volved, paint­ing is nor­mally a three-stage process. The first stage is a primer de­signed to cre­ate a uni­form base. Primer is now thin­ner than in the past thanks to ad­vances in sheet­metal stamp­ing, which has re­sulted in smoother sur­faces. Primer thick­ness is usu­ally 8 to 38 mi­crons (thou­sandths of an inch).

As the name sug­gests, base colour gives the body its colour. This too is thin­ner than be­fore, and the thick­ness ap­plied varies, like primer, be­tween 8 and 38 mi­crons. The top layer is clear-coat lac­quer. In­vis­i­ble as such, its role is to pro­tect the base colour from ox­i­da­tion by at­mo­spheric im­pu­ri­ties or degra­da­tion from ul­tra­vi­o­let light.

The ap­pli­ca­tion process is crit­i­cal if the fin­ished qual­ity is to be main­tained through the life of the body. Low paint den­sity oc­curs if the base coat is not al­lowed suf­fi­cient hard­en­ing: Porsche’s new sys­tem is par­tic­u­larly rig­or­ous in the length and tem­per­a­ture of its dry­ing sched­ules.

Mod­ern wa­ter-based paint pig­ment is not es­pe­cially hard. On Mohs scale of min­eral hard­ness, where talc is 1H, glass is 6H and di­a­mond 10H, paint is only slightly hard at 2H. Within this range OEMS vary in their choice of paint hard­ness. Mercedes and Volk­swa­gen use harder va­ri­eties; Porsche paint is usu­ally medium hard.

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