Tetra Gun Liquid Blue Blister Pack, 2.7-Ounce Tetra gun liquid blue is the best cold bluing formula in the gun market Recommended to use Tetra gun blue and rust remover as the pre-treatment Build up to seven layers of bluing based on how dark and rich you want the finish Results are almost immediate Tetra gun liquid blue is a chemical reaction that enhances the appearance of gunmetal Touch up or complete refinishing Restores your guns finish Easy to use Use it on tools and other Steel items