Petroleum based waxes are applied in molten or emulsion form to provide moisture repellent to wood composite boards (oriented strand, particle, hardboard, gypsum, and medium density fiberboard)

Paraffin wax was first produced commercially in 1867, less than 10 years after the first petroleum well was drilled. Paraffin wax precipitates readily from petroleum on chilling.  

Technical progress has served only to make the separations and filtration more efficient and economical.  

Purification methods consist of chemical treatment, decolorization by adsorbents, and fractionation of the separated waxes into grades by distillation, recrystallization, or both.  

Crude oils differ widely in wax content.