The first, and most important step to think about when beginning an acid stain project is preparation.  An investment in good prep will pay off in the end.  Before you begin, consider the following:

• Is your concrete smooth? or does it have some texture (such as a stamped pattern or a broom finish)? Acid stain will take better on textured concrete rather than smooth.  If your concrete is tightly troweled (very slick), you will need rough it up a little.  This can be done by grinding, sanding and/or  "Surf Prepping".
  

• Are there any stain blockers on your concrete? Wet the surface of your concrete to see if water absorbs into the surface easily.  If there are any areas where the water does not absorb, be aware that these areas may be blocked to stain as well.  Curing agents, sealers, grease, oil, paint, caulk, drywall mud, etc. can block the absorption of stain into your concrete. A curing agent is a "cure and seal" which could have been installed when the concrete was initially poured.  This is a bond breaker and will not allow the acid stain to react with your concrete.  All surface areas must be totally clean and free of any contaminants in order to receive a good reaction.  Likewise, if the concrete is existing, and you are remodeling, it is especially important that all prior floor covering adhesives are removed, as these can also be stain blockers.  We recommend Franmar Bean-E-Doo Mastic Remover and Soy Gel Paint Stripper.  These products are easy to use, work great and are soy-based. You can also use dry-grinding and/or scraping to remove the adhesives.  We have found that the Franmar products definitely save time and energy compared to using the elbow grease method.
  

• Is there a moisture vapor transmission issue? Too much moisture transmitted through concrete can cause sealer to delaminate.  You can test this by duct taping an 18-inch square of clear plastic on the surface of the concrete.  Check the plastic in 16 hours to see if there is any moisture present - if so, you may have a moisture vapor issue. If the moisture on the plastic is slight, you may be okay.  If there is a lot of moisture present on the plastic, you need to examine the drainage around the slab.  A great deal of moisture vapor transmitting through concrete can cause mold in carpet and pad, and can also cause tile to delaminate.  This issue must be addressed before proceeding to any flooring alternatives.
  

After the above considerations, you are ready to begin cleaning your surface.  A common misconception regarding acid stain prep is the use of muriatic acid to "acid wash" or "acid etch" the surface prior to staining.  This practice can sabotage your project and cause permanent, undesireable results.  Acid stain reacts with the lime in concrete.  If the surface is exposed to muriatic acid prior to acid staining, the lime is depleted by the muriatic acid, and the stain itself will have nothing to react with.

Instead, we recommend you use "Surf Prep", a product made specifically for acid stain preparation.  It removes stains from the concrete, and opens up the pores to give acid stain a better reaction and more color development.  The manufacturer recommends diluting 1 part Surf Prep to 3 parts water. If your concrete is tightly troweled and very smooth, you will need to use a buffer with a 60, 80 or 100 grit sanding screen to rough up the surface.  Then, you may use Surp Prep full strength, along with a heavy duty stripping pad to open up the pores and prep for acid stain.  All residue should be vacuumed, so contaminants will not settle back into the pores.

When your concrete is clean and dry, you are ready to begin staining.