Floor Finish

Acid-Stained Concrete:  Why Use A Floor Finish?

Acid Stained Concrete Floor

This acid-stained grocery store floor in the Detroit metro area has been well maintained.  Photo courtesy of:  Qualified Construction Corp.

Every successful acid-stained floor project requires a long term, protective, clear coating system. Choosing and applying the proper system, however, can be a daunting task to someone without a background in floor coatings or chemistry. Select the right system, and your floor will be easy to maintain and last indefinitely. Pick the wrong system, and problems will arise immediately and only compound themselves over time. Most people with an appreciation for acid-stained concrete flooring understand that it needs to be sealed. What is less well understood is the necessity and reasons for using a floor finish or “polish” on top of the sealer. Because of this common oversight by contractors and project owners alike there are many unsightly acid-stained concrete floors on display today in restaurants and other commercial locations throughout major metropolitan areas that serve as a visible deterrent to continued, expanded growth in the industry.

Spartan Floor Finish for Acid Stained Concrete

"iShine", a high solids floor polish from Spartan Chemical that  imparts maximum gloss, optical clarity, and durability to a stained concrete floor.

There are numerous, worthwhile benefits from using a floor polish that cannot be effectively achieved from concrete sealers alone. A good floor polish provides: 1) increased slip resistance; 2) increased water resistance; 3) good scuff resistance against black marking from shoes, furniture legs, and wheeled traffic; 4) improved lubricity so that stationary objects won’t stick to the floor; 5) a softer luster or feel to the floor; 6) good absorbency and deflection preventing the sealer from being chipped; 7) much shorter dry times than sealers; 8) buffability to restore gloss; and 9) ease in stripping. In short, the floor polish provides a very user friendly interface with the concrete sealer that can be easily repaired and maintained. This interface is frequently referred to in the industry as a “sacrificial layer”.

The sealer is just as essential to acid stained concrete flooring but is meant to be a more “permanent” protective layer. Consequently, its purposes are slightly different and more fundamental: 1) to enhance or deepen the color or tone of the stain; and 2) to provide long term protection for the design and floor color from harsher environmental forces, such as accumulated moisture, chemical spills, heavy abrasion, and repeat wear patterns. Unlike floor polishes, most sealers are very hard and well-adhered. They are not meant ever to be removed. Because sealers scratch and chip relatively easily, this means that they are difficult and time-consuming to repair. Using a floor polish helps to ensure that no damage is done to the sealer, and that ultimately no expensive fixes to the floor are ever required.

Carnauba Wax

Carnauba, a hard, natural wax used alone on floors in the early 1900's, it is now added to floor polishes to provide buffability and a deep, wet look gloss.

The basic difference between a sealer and floor polish is in the composition. A sealer is entirely composed of a resin or polymer, such as acrylic, epoxy, or urethane. A floor polish is primarily (80%) based on a resin or polymer; the difference lies in the addition of a natural or synthetic wax (10-15%). This addition of wax is responsible for many of the benefits outlined above. But the wax also makes the formulation of floor polish much more complex, and requires other ingredients:  modifiers (5%), such as dibasic esters, to make the polymer and wax compatible. Because of this complex formulation, applying floor polishes in the appropriate manner becomes critical. Specifically, a floor polish almost always needs be applied to a clean, dry, pH neutral, non-porous (sealed) surface in extremely thin coats, and within a certain range of temperature and relative humidity. If applied incorrectly, a floor polish may remain tacky, haze over, streak, or turn to powder.

Because floor polishes are more complex, manufacturers also generally carry numerous formulations (see Spartan Chemical's line) that vary in solids content, hardness, type and amount of polymers (acrylic & urethane) and waxes (natural & synthetic) used, chemical resistance, and depth and clarity of shine. Therefore, it is important to pick the right polish for the particular building environment and the anticipated maintenance program.  For example, not all floor polishes are buffable. As a result, buffing a polish that is not meant to be buffed may result in swirls and scratches, while neglecting to buff a finish that is meant to be buffed may result in quick yellowing and discoloration since these polishes are softer and accumulate dirt more easily.

High Gloss Marble Floor

Maintenance programs for marble floors usually include a "buffable" floor polish and a high-speed "burnisher" to preserve a high degree of gloss.

One great benefit of floor polish that not many people are aware of is its ability to adjust the gloss of sealed, acid-stained concrete. Most concrete sealers are relatively glossy. This look is generally desired in commercial environments, but the high light refraction can be bothersome to people in medical, institutional, or residential situations. Using two or more coats of a “matte” or “satin” floor polish on top of a concrete floor sealer will tone down its gloss considerably. Floor polishes are “matted” by using a particulate additive, (e.g., silicon), hard wax (e.g., polypropylene), dull resin (e.g, polyvinyl acetate), or a liquid compounds of these materials (e.g., silica gelled waxes). Also, because of the complex formulations involved, even floor polishes that have not been dulled in any way usually still vary in gloss significantly from one brand to another.

Acid Stained Concrete Floor With Matte Finish

This acid-stained entertainment room floor is a good example of the dull or "matte" sheen that can be achieved with a matte floor polish or low gloss sealer.  Photo courtesy of:   Alpine Concrete .

Sealers can also be used to dull a stained concrete floor’s gloss. But there are several common problems with this approach. Most sealers are flattened by using fine particles, such as silicon, talc, chalk, metal soaps, or polymer beads. These particles tend to coagulate and/or settle out of suspension in a sealer during application. The result is often a streaky or seedy look to the floor with uneven, isolated patches of gloss.  This can also be a problem with floor finishes, but the use of a wax in the formulation aids in the dispersion of the flattening particles and helps suspend them near the surface.  Another problem with the use of flattening particles in sealers is that they tend to interfere with strength and durability, making them more brittle.  This can lead to flaking and delamination of the sealer, a common problem with stained concrete floors.  This brittleness is not a problem with floor polishes because the wax component usually makes up for any loss in plasticity due to particle additives.  Finally, sealers can be dulled by using certain resins, such as treated acrylics or polyvinyl acetates, or by including chemical (usually acidic) modifiers. These sealers, while a little more durable than those flattened with particles, are still less durable than typical gloss sealers, and usually can only be dulled slightly, to a “satin” rather than full “matte” appearance.

Metroflor's "Matte Finish" can be used with most concrete sealers.  The company makes its own line of tile and wood flooring products..

With the growing popularity of acid-stained concrete, home and business owners are beginning to fine tune their preferences with new flooring projects, not only in terms of design but gloss as well. Accordingly, we at Premier Veneers have tested and experimented with several matte floor finish products over the past year. We favor Matte Finish" from Metroflor, available at most Home Depots. It dulls a glossy stained concrete floor very nicely, doesn’t streak, and is easy to apply. We sometimes use and recommend Spartan polishes where a gloss finish is suitable, and they do have a matte product also: Matte Floor Finish. However, it is formulated somewhat differently than Metroflor's, and it is not nearly as effective. We have evaluated the matte polishes from several other companies as well, such as Johnson, EcoLab, and Glaze 'N Seal, and these products fall into a third, fourth, and fifth tier because they use particulate additives rather than dibasic esters, and these particulate additives vary in size from large to small, which is the least effective size for modifying gloss.

In conclusion, a good floor polish is always necessary on top of a properly sealed acid-stained concrete floor. It will help preserve the floor’s initial appearance and condition indefinitely. Furthermore, because floor polishes are so inexpensive (about $15 per gallon) and easy to apply there is no reason not to use one. Given their complex formulations, however, it is imperative always to test polish on a small area of sealer for compatibility before doing an entire floor and then to follow the manufacturer’s application instructions as closely as possible.

Further reading:

What's in a Floor Finish
Evolution of Floor Finishes
Birth of a Floor Polish
Maintenance of Stained Concrete Floors


 Aug/Sept 2008                    Dec/Jan 2009