There are four ways to add color to slabs that are intended for polishing.
Color pigments that are added to the design mix prior to pouring.
Dry Shake Hardener
A cement-rich, dry, topical hardener that is applied evenly to a freshly troweled new slab. The water from the slab reacts with the hardener to create a hard, dense surface.
A translucent stain with a range of eight earthen colors whose metallic salt component reacts with the calcium hydroxide that is created during hydration. The colors are naturally variegated and mottled due to inconsistent levels of calcium hydroxide in the slab.
Dyes, as opposed to pigments, are minute colorants that produce a transparent coloring of the concrete as they penetrate the concrete and attach themselves to the crystalline structure in the concrete. Pigments, in contrast, are larger substances that produce an opaque, topical coating similar to paint.
A test slab with four sample colors of a dye, made for the benefit of a client. Dyes and acid stains both produce translucent colors, so the slab’s original color will affect the appearance of the final color. Colors will appear more vibrant on light or white concrete and more muted on darker colored slabs.
Confirm whether your customer expects cream or aggregate, and then establish if the mix design and your equipment are up to the task.
When coloring with dyes or acid stains, only a pre-test will allow you to settle on whether one application or two applications are necessary to achieve your desired color.