Medium density overlay panel, or MDO panel, is a paintable surface made of plywood with a weather-resistant resin overlay bonded to the wood by heat and pressure.The overlay, which has 28% resin content, resists water, weather, wear and degradation.

Development

Originally developed for sign painting and concrete

Concrete

Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...

 formwork

Formwork

Formwork is the term given to either temporary or permanent molds into which concrete or similar materials are poured. In the context of concrete construction, the falsework supports the shuttering moulds.-Formwork and concrete form types:...

 industries, MDO is also used for other applications as a paintable surface. Paint finishes on MDO are up to three times more durable than the same finish applied to ordinary plywood
It is a plywood product, with a paper face overlaid on the plywood substrate

Substrate

Substrate may mean:*Substrate , Natural stone, masonry surface, ceramic and porcelain tiles*Substrate , the material used in the bottom of an aquarium*Substrate , the material used in the bottom of a vivarium or terrarium...

 with an exterior grade (usually) phenol

Phenol

Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...

ic adhesive. MDO is designed to have a smooth, paint-receptive surface. One or both faces can be surfaced with paper, and is produced in 4' x 8' sheets from 3/8" to over an inch in thickness.