A concrete release oil is a coating, usually applied to a solid surface, that prevents adhesion of fresh concrete to it. It is usually a petroleum oil or an oil emulsion.
The use of form release agents is widespread in construction. They are used on wood, steel, and aluminum molds to prevent the stickiness of freshly poured concrete.
Light-bodied (low viscosity) petroleum oils, emulsions, or waxes are often used as release agents for forms and molds made of wood. They have the advantage that they are non-staining and non-corrosive to the concrete and the mold surfaces.
They are easy to apply and can be used for a variety of projects. Some contain wetting agents to dissipate the oils so they won’t bead up on the forms and produce bugholes.
There are also chemically active agents based on fatty acids that react with the free lime in concrete to produce soaps that continue to act as a release agent during the concrete curing process. These are often a little more expensive than plain oil products but they can be more effective and have the added benefit of being environmentally friendly.
A good quality release agent should be non-staining, non-corrosive to the forms or other surfaces it comes into contact with, and have a sufficient stripping strength to allow clean removal of the form from the concrete during stripping. This is the primary function of a release agent, but other important functions include protecting the form from damage and reducing machine cleanup time.