“Alkyd Resin” is a polyester resin obtained through heating an oil (fatty acid) with an alcohol (glycerin, pentaerythritol,…) and an acid (phthalic anhydride, …) in presence of a petroleum solvent. Resins play the main role in forming the final film and they have various physio-chemical properties and usages depending on raw materials applied and the oil content. Alkyd resins are the dominant resin used in most of oil-based paints and varnishes.