Birchwood Technologies Presto Black® BST4 Brush-On Liquid

Article number: 74BST4
Availability: In stock (15)

PRESTO BLACK BST4 Brush-On Blackener

Operating Instructions


PRESTO BLACK BST4 is a liquid brush-on blackener for all iron and non-stainless steels. Applied at room temperature by swab-on or spray techniques, the BST4 reacts quickly and produces a non-dimensional black finish in 30-90 seconds. The finish can be sealed with a protective oil and is suitable for use on precision tooling and machine components. Or, the black finish can be highlighted to produce a pleasing distressed or antique pewter type finish on decorative metalwork, architectural trim or hand-forged items.


In short, the surface must first be thoroughly cleaned of all oil and excess scale. The black finish is then applied, rinsed, dried and sealed with a topcoat appropriate to the end use of the article:


  1. CLEAN the metal surface, using a solvent that does not leave a Use alcohol, acetone, lacquer thinner or equivalent (Do not use mineral spirits or kerosene).
  2. REMOVE OXIDES, if necessary, by bead blasting, or use other abrasive cleaning methods, such as buffing with Scotchbrite abrasive pads or flap wheels.
  3. APPLY PRESTO BLACK BST4 solution to the metal surface by brush, swab or spray techniques (using a plastic pump sprayer). For best results, apply a thin film of solution on the surface, and then re-apply a few more times during the course of the reaction in order to “replenish” the supply of chemicals working on the A light-duty flooding technique usually works best. For large surfaces, apply the BST4 solution with a wide applicator or with a pump sprayer to facilitate wetting a larger area in a few seconds. Continue application until a uniform gray/black finish is achieved. DO NOT LET THE BST4 SOLUTION DRY ON THE SURFACE, or flash rusting can occur.
  4. STOP the REACTION by sponging the surface with water to remove blackening residues. Note: Flash rusting can occur easily, at times. To avoid the flash rusting, have a baking soda solution pre-mixed and ready to apply as a second rinse (mix 2 tablespoons per gallon of warm water) to neutralize the This will inhibit the rusting tendency.
  5. FORCE DRY the surface with compressed air or warm air to speed
  6. SEAL the surface with a topcoat appropriate to the use of the article: Tooling/machine parts can be sealed with a water-displacer, such as DRI TOUCH AMBER IRP2. Decorative surfaces can be highlighted, if desired, with Scotchbrite pads, to produce a distressed or antique finish, then sealed with a clear, satin lacquer. Or, for light-duty, indoor pieces, use paste wax.

Before Using This Product – Please Read, Understand and Follow all the Precautions shown on the Product Label and on the Safety Data Sheet.


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