Vinyls are generally manufactured in one of two ways: “calendering” or “casting”. While they appear similar at first glance, there are distinct differences. Their thicknesses are both measured in mils.
The differences are in the manufacturing processes and also in the plasticisers and stabilisers used to manufacture them. Cast vinyls are manufactured in a less stressed process than that used in the manufacture of calendered vinyls.
Cast vinyl material is made with the vinyl starting as a liquid. The liquid is poured as a thin sheet, like a very precise waterfall, onto a roll of mylar. The liquid is dried on the mylar, then adhesive is added, and then a liner. The advantage to this method is a very thin vinyl that has no memory. It can be stretched and pulled over corrugations, rivets and compound curves. Cast vinyl also generally has better dimensional stability, color pigmentation, UV stability, and higher gloss levels.
Calendered vinyl material is made with the vinyl starting as a dough-like solid. The vinyl is pressed out through a series of rollers, becoming thinner and thinner. When the final thickness is achieved, the adhesive is added and then the liner. The advantage to this method is cost. You get a product suitable for flat or slightly curved surfaces at a budget price.