Coloring Vertical Surfaces with Color Hardener Slurry

By Chris Sullivan – ChemSystems, Inc.

Question:

I plan to use a color hardener on the faces of a set of stairs. I have been told that it's easier to apply color hardener to vertical surfaces by making a slurry with it. Can this be done, and what consistency should the slurry be?

Answer:

Yes, color hardener can be used to make a slurry for coloring vertical surfaces. This process is most often used when "facing" the front of steps or the vertical edges of stamped concrete slabs. An advantage of this method is that you can color the vertical sections as time permits, even days later if necessary. That makes it a convenient alternative on projects with lots of steps or vertical surfaces and not enough time or labor available to remove the forms and finish those vertical faces while the concrete is still workable.

The process involves mixing color hardener with a 1-to-1 mixture of water and a concrete bonding agent. Add enough color hardener to achieve a consistency similar to peanut butter or a stiff paste. Before applying the slurry, remove the forms and work the surface with a wood or resin float to create a rough surface for better adhesion. Apply the color hardener slurry with a small trowel or float, as if icing a cake. When the slurry sets up, trowel it smooth and then use a stamp or skin that matches the corresponding flatwork sections. A common mistake is starting the finishing work too early, while the slurry is still wet. Wait until the slurry reaches the optimum stage for stamping or finishing so it will take a good imprint. At this point, cleaning and sealing can proceed as usual for the entire project.

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