The ‘Madison formula’ was developed at the Forest Products Laboratory around 1950 as a simple linseed-oil-based finish that could be made from readily available components. It was one of the first formulations of its type – a penetrating finish that eliminated the problems with cracking and peeling commonly found with the oil-based paints available at the time. The finish could be made with pigment to give a semitransparent stain or without pigment to give a water repellent preservative.
Commercial oil-based semitransparent stains are available in a wide range of formulations, all of which must comply with EPA rules that restrict the amount of solvents or volatile organic compounds (VOCs). The stains are formulated with or without a registered pesticide (fungicide). If the stain contains a fungicide, it is usually labelled as a “preservative.” Many modern commercial finishes are better than the Madison formula, particularly those that are formulated with modified linseed oil. The finish should have the following attributes.
- Be oil-based
- Contain about 10% to 20% alkyd or similar resin
- Contain an inorganic pigment
- Be solvent-based
- Contain a fungicide
- Include 1% to 2% wax or a similar water repellent.
For more on Alternatives to the ‘Madison formula’, including information on other stains, water-repellent preservatives, and a formulation for a simple homemade water repellent finish, just follow the link!