The first stage involves evaporation from the time the paint leaves the gun until it reaches the vehicle. Paint solvents evaporate at three differing stages. These rates control liquidity and help regulate drying (evaporation) and curing. Paint thinners or reducers are chemical compounds that evaporate at different rates. Solvents both dissolve the rosins and suspend the pigments, making it possible to move the paint from the mixing table, through the gun and onto the vehicle where the solvents evaporate. Solvents are called the coating's "vehicle" by paint chemists. Though painters use it each time they reduce paint and should be making choices as to which one they should be using, depending on the spray conditions, they often try to make choices without knowing how solvents work. This category of paint components is highly misunderstood. Knowing your system and following the prescribed recommendations is very important. Some manufacturers provide a mixture of balanced toners and non-balanced ones. Others do not have rosins in the toners and must have one added before they can be applied as a basecoat. That is, the toners on the mixing rack have the rosins in them and can be taken off the shelf, reduced and applied as a basecoat. The way that paint systems deliver their rosins also differs between manufacturers. Therefore, many collision repair businesses choose a vinyl wash primer (acid etch) for their direct-to-metal corrosion protection. Its disadvantage is that it takes time to apply. For example, epoxy has excellent adhesion qualities and when teamed with a corrosion resistant pigment provides an outstanding corrosion-resistant base. These different rosins have their advantages and disadvantages. Rosins such as acrylic urethanes, epoxy and polyester are each suited to specific situations. The type of rosin determines the durability and other properties of the coating. In more modern times, rosins were produced from synthetic hydrocarbons (petroleum). In the past, rosins were produced from oils (linseed oil, from flax, for example), and then from tree saps, such as varnish. These are the film-forming components of a coating that help provide gloss, durability, flow (rheology) and adhesion. They bind the pigments to the substrate below it. Rosins, sometimes called binders, do just that. It is these solids, with the help of rosins, that not only look good after they are cured but provide protection and long-lasting resistance to the elements – a vital part of a coating's job. When a coating is referred to as a high-solids paint, it is high in pigments, the substance that remains after the paint cures. Pigments make up the bulk of the solids in the paint. Most extenders are translucent and therefore do little for opacity. Other "pigments," called extenders, provide properties such as filling and sandability as in primers, adhesion and corrosion protection. Pigments also add to the coating's glamour with metallic, pearls (mica) and color shifting materials. The pigments that create color are finely ground naturally occurring minerals or manufactured products that add to the color and its opacity (how well it hides or covers). Though most painters think of the pigment as the "color" (and often it is), pigment also contributes to the hiding ability of a coating, its filling properties (the filler in primer filler is technically a pigment) and its sandability, adhesion, corrosion resistance and durability. Each of these components contribute significantly to the performance of the coating, either as it is being applied or during its lifespan (holdout). Solvent-borne paint has four basic components: pigments, rosins or binders, solvents and additives. Knowing how paint performs under certain conditions - and controlling those conditions to our advantage - is a necessary part of producing great paint jobs. To be good at what they do, painters in today's demanding market need to know how and why paint components work. Many of the components are the same, but nearly as many have changed, and new ones have been added. Those of us who have been painting for some time know all too well that the most constant part of paint technology is that it's constantly changing. Turn out your best work with a nuts and bolts understanding of these paints
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