Traditional steel blackeners were too toxic for the environmental sustainability goals set for the new Multifaith Center at Wellesley College. Alternative finishes include non-acidic steel patinas formulated from dye-oxides, tinted metal sealing waxes that are applied hot or cold, a series of lacquers and clear coat paints/sealants, and linseed oil. These different categories of finishes were tested in combination except for lacquers with waxes since both are final top-coat sealants for metal. Permalac was the choice. Check out the article.