Monday, June 20, 2011

How do I open the pores of really smooth interior concrete?

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Q. -  For indoor staining on smooth concrete, does anything besides the cleaning need to be done? some instructions I have read say it is necessary to use an etching agent or floor buffer with sandpaper to roughen the concrete before it will take stain
Hello Rachel,
 A. -  The concrete needs to be clean, and the pores need to be open, so it can accept the stain. So if it the concrete is slick like a mirror then you need to open the pores. If it is smooth but not super slick and/or has been around for a while, then the pores may be open enough already.
   Here's how to tell: Pour some water on it. If the water soaks right in, then the stain will too. If the water just kinda sits there and has a hard time penetrating the concrete's surface, then the stain will too.
   If you see that you do need to open the pores, then you should not use, never ever use or do, any acid washing or acid etching if you can anyway keep from it, prior to staining. When you acid wash/etch concrete then it burns up the lime and other minerals that are present in the concrete, and needed by the concrete acid stain in order to react and work properly. Most acid stains are rendered useless once concrete has been acid washed/etched. In fact, the Artist Grade line of Concrete Acid Stain by Concrete Camouflage is the only acid stain proven to still be effective on an acid washed/etched concrete slab. But even then, it can be not quite as rich as it would have otherwise been.
   Anyway, to open the pores: Yes, you can use a rented floor buffing machine as you had read elsewhere. However, do not use the sanding disks unless you're trying to get up glues, paints, etc. Only then would you need to use them. Of course the sanding disks will certainly open up the pores, but they will also take out some of the marbleization found in the final effect of stained - smooth concrete. 
   Therefore, if you're concrete just needs cleaned well and the pores opened up, you're better off to use the good scrubby pads instead. They will still clean the concrete well and open the pores up adequately, without over opening them, and thereby causing the loss of marbleization.
I hope this helps.
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