Resins are used as binders in inks, and differ by the type of ink being produced. Natural resins include rosin- and shellac-based resins. Hydrocarbon-based resins are derived from petroleum, and are used primarily for oil-based inks for offset printing. Alkyd resins are also used for oil-based resins. Liquid ink resins include alkali soluble such as styrene-acrylic and styrene-maleic anhydride.