PRESTO BLACK® BST4 Brush-On Blackener

New PRESTO BLACK® BST4 brush-on liquid is a fast acting, cold blackener for all iron and non-stainless steels. When applied to any clean ferrous metal surface, the BST4 solution blackens within 30 seconds and forms a durable, black finish that can be topcoated to form an attractive, protective black oxide finish. In the machine shop, PRESTO BLACK BST4 liquid serves as a fast-acting blackener of re-machined areas or reworked metal parts. It’s ideal as a quick repair for scratches or damaged areas on parts previously black oxide finished. For these applications, just degrease the surface with a cold solvent wipe (alcohol, acetone or lacquer thinner) and then apply the BST4 liquid with sponge or swab and allow it to work. When the surface has turned sufficiently black, the liquid is rinsed off with cold water and a water displacing rust preventive oil is applied for maximum corrosion protection. The resulting finish has a good black color that blends well with existing black oxide finishes and will withstand the same degree of salt spray exposure as the original black oxide. The PRESTO BLACK BST4 liquid can be applied to any type of tool steel in the tool room, inspection or main production areas.