Acid vs. Alkaline: What, Why and When?

Acid vs. Alkaline: What, Why and When?
By Jasen Santiago

As we all know, cleaning the floor is an essential step in the tile and grout restoration process. In most cases, however, this important first step acts only as a prepping stage in bringing the floor to our customer’s desired result. Whether we are looking to revive an old, dingy floor back to its original lustrous finish, provide a customer with a sealant to protect their investment, or completely change the appearance of an existing tiled floor, the cleaning process is going to be the determining factor as to how well our jobs turn out. So what is the best way to prep our floors? Using an alkaline cleaner? Using an acid cleaner? Or maybe the most effective solution is to use both. These are common questions often debated by many tile and grout professionals. While there are too many factors involved to determine the right answer, with proper education it is possible to determine the right answer for you.

To answer the “acid vs. alkaline” debate we must first discuss the purpose of both of these cleaners. Alkaline cleaners or cleaners with a pH level higher than 7, are often used as the sole cleaning agent in the tile and grout restoration process. Alkaline cleaners are formulated to loosen the bond between simple waxes, vegetable oils and animal fats from the surface we are cleaning. The primary advantage of high-pH cleaners is that they are effective cleaners, even on the most tenacious soils. Alkaline cleaners are also recommended when there is a large amount of soil to be cleaned. Additionally, alkaline cleaners can be used in almost any operation, but will not do anything to remove mineral deposits, rust or hard water stains. Also, when you’re prepping old surfaces for topical or penetrating sealers, alkaline cleaners will do little more than remove the soil from the substrate. This is where acid cleaners come into play.

Sometimes, when prepping old surfaces for sealing, etching the substrate may be beneficial. While alkaline cleaners do a great job of removing surface debris, acid cleaners, or cleaners with a lower pH level than 7, will directly work with the bonding agent in calcium carbonate based surfaces. Etching the surface is going to expose new pores providing some extra “tooth” making the product-to-surface bond as strong as possible. This will make any sealer more effective and in most cases, will make color sealing more efficient. Acid cleaners may also be used to remove tarnish, alkaline discoloration and corrosion, remove hard water deposits from many surfaces, and will neutralize alkalis. Being that acid cleaners are used to remove calcium build-up, they should not be used on calcium based stones such as marble, travertine, and limestone as they will also damage those surfaces.

So what is the bottom line? When do we use alkaline, when do we use acids, or when is it appropriate to use both? The answer to this question is going to be job specific and will depend on a variety of things. What type of surface are you restoring? Which kind of stains are you trying to remove? Or what final result are you looking to provide your customer? On many jobs, using an acid cleaner won’t be necessary. Cementitious surfaces, such as grout or concrete, harden (or become less porous) overtime with the addition of moisture. It’s in these situations where etching the surface is going to make a significant difference. However, on newer surfaces, cleaning with an acid may be overkill and unnecessary. On that same note, using an alkaline cleaner may also be an unnecessary step. Many times grout will become discolored due to years of mopping improperly, but will not have a considerable amount of dirt and debris on the surface. In these situations, a test patch should be conducted to determine whether or not the grout is exposed enough to react with the acid, possibly saving yourself a cleaning step. If the cleaner immediately “fizzles” when applied to the surface, continue the cleaning process using only an acid to start the restoration process. However, if you get little or no reaction with the acid, this is an indicator that you must first remove the soil with an alkaline cleaner to expose the grout, making it a two step cleaning process.

While the great dispute of “Acid vs. Alkaline” will continue on, I hope this article will at least shed some light on the subject. If nothing else, just to provide you with some ammo for the next time you find yourself in the middle of this classic debate.

One Response to “Acid vs. Alkaline: What, Why and When?”

  • Hey Jason, Great job as usual. Your help and availability is why I use MST’s products besides the fact that they work!

    Is there a way to remove the tarnish or stains in grout left after cleaning with alkaline on travertine, marble, flagstone tiles without dulling or etching the stone?

    Chuck