This is the basement of a brand new home in the upscale community of Birmingham, Michigan. The owner plans on staining the wood stairs black and wanted the concrete floor stained close to black to match. We used a very dark brown acid stain, including lighter tones of the same color so that the floor didn't end up looking like "black paint".
Above left, the concrete looks to be in good shape at the outset of the project. But drywall mud, white primer, yellow spray insulation, and clear liquid nails are hard to see on concrete unless it is wet. We wet scrubbed and scraped the floor for 3 days to get these contaminants off the floor and then set up a dehumidifier and blower fan (above right) to dry the floor.
After masking the walls with plastic, we applied two coats of Brickform Ebony acid stain at a rate of about 375 square feet per gallon and then rinsed the excess residue (above left), before applying two coats of clear polyurea sealer containing fine aluminum oxide for slip resistance and to slightly dull the high gloss (above right).
Prior to the start of the project, we did color samples of several companies' versions of "black" acid stain, in a utility room, for the customer to choose from. The next day, we applied sealer. Although similar, the stain colors do vary slightly, and we wanted to make sure the color we used would have the right tone but not be so dark as to prevent any "mottling" effect.
The photo above left shows a perspective from the other end of the basement. The color and "mottling" effect turned out well, and with the careful masking using plastic sheeting we were able to keep the stain off the walls and wood stairs. One great thing about acid stain it that even makes small areas, like closets (above right), look fantastic.
The last two photos above illustrate a major risk assumed by any homeowner in trying to make acid staining a do-it-yourself project! Some contaminants are hard to see even when concrete is wet and show up as major blemishes after staining and sealing. This is what happened in the bathroom (above left).
We were able to use solvent-based tints to blend these remaining blemishes in with the rest of the floor (above right). These blemishes consisted primarily of drywall mud, paint and wall primer that made its way into the pores of the concrete and became invisible against the whitish gray cast of the concrete.