Release Powder Causing Sealer Discoloration

By Chris Sullivan – ChemSystems, Inc.

Question:

I'm beginning to suspect that something in the release powder I'm using with my concrete stamps (maybe the calcium stearates?) is causing sealer discoloration. Have you observed this? It seems to happen more with particular charcoal-gray releases. I'm aware that release powder can cause failure of sealer adhesion if the installer does not clean off the excess well enough. Do you have any other advice?

Excess release powder causes the
sealer to fail and discolor.

Answer:

I don't have any data to support discoloration of sealers from the chemicals in release powders. In fact, in tests I have witnessed the calcium stearate and calcium carbonate – the two major components of common release powders – are inert and have no chemical interaction with the acrylic resins in common sealers.

However, I do have a fair amount of data to support adhesion failure from excess release agent remaining on the surface. Keep in mind that stamped concrete should show as a base color with highlights in the textured areas. Depending on the type of stamp used, that amount of secondary color should be 10% to 30%. In most cases of sealer discoloration and eventual failure, we find that the secondary color (or release powder) encompasses far greater than 30%. Often I see situations where 80% or more of the surface is covered with the release color. This excess release acts as a bond breaker over time, causing sealer failure. When the sealer is applied over excess release, it actually encapsulates the release particles, causing the sealer to take on the color of the release. This may be the discoloration you are witnessing.

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