Marshall's Spot-All Liquids are for retouching, spotting, coloring, and correcting photographic prints and black& white negatives. These dyes are invisible with rapid drying. They can be used on most film and glossy or matte photographic paper.
Spotting, which refers to the retouching of small imperfections in a print, is usually done before you begin to hand-color.
These most often appear as small white dots on the print. They are caused by dust that can be difficult to avoid completely in the printing process. By mixing a few drops of Marshall's Spot-All Liquids you can match the tone of pretty much any neutral black and white, or even toned print.
Using a very fine brush such as a 000 size, dilute small amounts of the mix water, creating a tone that is lighter then the area surrounding the dust spot.
Touch the brush to a paper towel or tissue, so that it is not overloaded with the liquid. Apply one small dot at a time to the white spot, gradually filling it in, until it matches that section of the print and disappears.
1/2oz bottle of Blue Black dye with built in dropper.