Car paint TIL ( possibly relevant to any metal substrate, and then some ) :
// CHEMISTRY //
- BEWARE ambiguous terms : LACQUER, ENAMEL, RESIN are all non-specific labels which may refer to a very wide variety of formulations
- CURING time : paints require days or months to fully cure, so leaving a WEEK between layers may help for DIY projects, especially if you don't have a car-sized oven
- HARDENERS : anything which requires you to mix two parts ( usually 1-2% hardening catalyst ) is likely to be stronger than a one-part product; but this is not absolutely guaranteed to be true
- DURABILITY : [ ( stronger ) : polyurethane > epoxy > acrylic > nitrocellulose : ( weaker ) ], paint formulations typically have a mix of these chemicals; branding of the product might highlight one chemical over the others; polyurethane (PU) is generally regarded as having the highest durability, particularly against ultraviolet radiation
// MECHANICS //
- SANDING : always address the substrate before applying the layer over it; wet or dry methods may apply
- 1 : lower layer : "body FILLER" x "putty" : the structurally strongest stuff is a { polyester resin, hardener, fibreglass } concrete ... this method is used to build entire car bodies, in some cases ; otherwise it is usually just for smoothing out cavities
- 2 : lower-mid layer : PRIMER : the main role here is to protect metal from rusting, and to provide adhesion to upper layers ... the stack is usually [ metal OR filler > PRIMER > pigment > clear ], however [ metal > PRIMER > filler > PRIMER > pigment > clear ] also works
- 3 : higher-mid pigment : whatever ... see CHEMISTRY, above
- 4 : top layer : clear coat ... see CHEMISTRY, above
- 5 : super top layer : clear polymer or ceramic coatings ... are regarded as "not paint" but basically play the same function, and should be regarded inclusively with paint maintenance; these are commonly applied with a cloth, using a special method
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