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Concrete vagaries

September 1, 2010
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You’d think something like concrete would be predictable, or, well, concrete.  Alas, it is not so, not in the construction material or, if you ask Tom, Ted Drewes. He swears they changed their recipe a few years ago and their concrete just isn’t the same anymore. In the case of our project, we have some visible examples of how unpredictable concrete can be when you are trying to change its color.

The floor finish guy has done a few samples of the options we are considering for the concrete floor stain. We were thinking it would be interesting/dramatic to darken the floor to almost a black color. We taped off a corner of the room, where we plan to install tile on the bathroom floor, to see how the chemical stains would look on our very old concrete floors.

Green and clear finish samples, still wet

We have five samples to consider- a light green, clear sealer, and three shades of the black stain. The green is a color that works pretty consistantly, but I’ve never used the black stain before. I think we know now

why you don’t see it used much.

The stains are chemicals that react with the cement and minerals in the surface of the floor slab. Because the mix materials in concrete can vary a lot, especially in a floor that is about 85 year old and had who knows what spilled on it, the chemical reaction may not go as expected. The black stain looks bright yellow when it is first applied. Unfortunately, we don’t have a photo of that. As it reacts and dries, it darkens and changes color. In our case, the color changed to a muddy, slotchy brown. It kind of looked like the floor before we cleaned off the old hide glue. It is not a look we’re interested in making permanent.

Cleaned and dried stain samples

Concrete floor before cleaning

The green isn’t bad, but we can’t imagine we would be happy with a green floor forever.  We decided to keep it simple and skip the stain. The floors and base will be polished and a clear sealer applied.

So, why were we trying to change the floor? It seemed like a good idea at the time, but one of the things we are learning about the B.A.B is that it doesn’t easily change. It is a good idea to stick with the simple solution. And the clear finish looks great with the cleaned-up window mullions.

Clear finish with galvanized mullion

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