PAINT INGREDIENTS
Paint is made up of four main classes of ingredients: pigment, resins, solvents and additives. The pigment gives the paint its colour, and can be either natural if it was dug from the ground, or synthetic if it has been artificially created. The all-round performance of a paint is provided by resins though, the component that binds the paint together on the panel. It is the resins that have most to say about how the paint has to be applied, how it dries and how durable the finished result is.
Starting with cellulose, this is a thick product which needs plenty of solvent to thin it down far enough for spraying. It is a popular DIY option because it dries in minutes and so limits the risk of airborne contaminants. It also poses little direct health risk to the user, and it is relatively easy to polish out blemishes in the finished article, or to make localised repairs as the dry paint will re-dissolve into fresh solvent.
Synthetic resins can be derived from a number of sources. They all dry by oxidation, which causes them to skin over quickly but remain soft underneath for up to 48 hours as the oxygen works its way down through the paint. This slow drying time is one of the main drawbacks of synthetics, but they remained a mainstay of commercial vehicles for decades because they are flexible enough to resist stone chips, are resistant to chemical attack and retain a good gloss with nothing more than a wipe over with a damp leather. Synthetics are oil-based and do not take to being oversprayed with cellulose or two-pack, the thinners in these being liable to cause the paint below to wrinkle and lift.
Acrylic resins may be either one-pack or two-pack. The one-pack acrylics are much like cellulose paints in their coverage and drying behaviour, and while the finish is more brittle and thus liable to chipping, the gloss is more durable. Two-pack acrylics rely on a chemical reaction
