Acid-Stained Concrete: Why Use A Floor Finish?
Every successful acid-stained concrete flooring project requires a long term, protective, clear coating system. Choosing and installing 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 almost immediately and compound themselves over time. Most people with an appreciation of acid-stained concrete flooring understand that it needs to be sealed. What is less well understood is the necessity to use a floor finish - or “polish” - on top of that sealer. Because of this common oversight by contractors and project owners alike, there are many unsightly, damaged, acid-stained concrete floors on display today, in restaurants and other commercial locations in major metropolitan areas, that serve as a visible deterrent to the continued growth in use of this great flooring system.
There are numerous worthwhile and even essential benefits to be gained from using a floor polish that cannot be derived through use of a concrete sealer alone. Specifically, a good floor polish provides: 1) increased slip resistance; 2) increased water resistance; 3) scuff resistance against black marking from shoes, furniture legs and wheel traffic; 4) improved "lubricity" so that stationary objects don’t stick to the floor; 5) a softer luster - or "feel" - to the floor; 6) good impact absorbency and deflection, preventing the sealer from being chipped; 7) much shorter dry times than sealers; 8) easy "buffability" to restore gloss; and 9) ease of stripping and replacing. In short, floor polish provides a very user friendly interface with a concrete sealer that can be easily repaired and maintained. This interface is frequently referred to by the industry as a “sacrificial layer”.
FLOOR FINISHES VS. CONCRETE SEALERS
A clear film-forming sealer is just as important to acid-stained concrete flooring as floor finish, but it is meant to be more of a “permanent” protective layer. Consequently, the sealer's purposes are slightly different and more basic: 1) to enhance or deepen the color - or "tone" - of the stain; and 2) to provide long-term protection for the floor color and design from harsh environmental forces, such as accumulated moisture, chemical spills, heavy abrasion and repeat wear patterns. Unlike floor polishes, most concrete sealers are very hard and well-adhered to the surface. They are not meant to be removed. And because concrete sealers chip and scratch relatively easily, this means that they can be difficult and time-consuming to repair. Using a floor polish helps ensure that no damage is ever done to the sealer and that ultimately, no expensive fixes to the floor are ever required.
The basic difference between a sealer and floor polish is in the composition. Sealers are entirely composed of a resin or polymer, such as acrylic, epoxy, or urethane. Floor polishes are primarily - about 80% - based on a resin or polymer, but the difference lies in the addition of a natural or synthetic wax -approximately 10-15%. This addition of wax is responsible for many of the essential floor polish benefits outlined above. At the same time, this wax also makes the formulation of floor polish much more complex, and therefore, it 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 an appropriate and specific manner becomes critical. Specifically, floor polishes always need to 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 (to a "white" appearance), streak, or turn to powder.
NOT ALL FLOOR FINISHES ARE THE SAME
Because floor polishes are more complex than sealers, manufacturers generally carry numerous formulations (see Spartan Chemical's product line) that vary in solids content, hardness, type and amount of polymers (acrylic & urethane) and waxes (natural & synthetic), chemical resistance and depth and clarity of shine. Therefore, it is very important, at the outset, to pick the right polish for the building environment and 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 buffable polishes are softer and accumulate dirt more easily.
One great benefit of floor polish few people are aware of is its ability to adjust the gloss of sealed acid-stained concrete. For example, most concrete sealers are relatively glossy. This look is generally desirable in commercial and residential environments, but the high light refraction associated with gloss sealers can be bothersome to people in medical and institutional settings, or simply unappealing to project owners interested in a "warehouse look" floor. Using two or more thin coats of a “matte” or even “satin” floor polish on top of a sealed concrete floor will tone down its gloss considerably. The way floor polishes are “matted” is by using a particulate additive, (e.g., silicon), hard wax (e.g., polypropylene), dull resin (e.g, polyvinyl acetate) or liquid compounds of these materials (e.g., silica gelled waxes). Also, one thing to keep in mind is that because of their complex formulations, even floor polishes that have not been dulled in any way usually still vary considerably in gloss from one brand to another.
SEALERS NO SUBSTITUTE FOR FLOOR FINISH
Like polishes, sealers can also be used to dull an acid-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 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 wax in their formulation aids in dispersing 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, thereby making a sealer more brittle. This can lead to flaking and delamination of a sealer - a common problem with stained concrete floors. "Brittleness" is not a problem with floor polishes, by contrast, because the wax usually makes up for any loss in plasticity due to particulate 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.
With the growing popularity of acid-stained concrete, home and business owners are beginning to fine tune their preferences when planning new flooring projects - not only in terms of design but gloss, as well. Accordingly, Premier Veneers has tested and experimented with several matte floor finish products. We favor Carefree Matte, by Diversey. It can be found online or at local janitorial supply houses. XL Matte Floor Finish, from XL North, is also available online. Both of these floor finishes dull a glossy stained concrete floor very nicely, don’t streak, and are easy to apply. We routinely use and recommend Spartan brand polishes, and they just introduced a new matte floor finish, called PROmatte. We have evaluated the matte polishes from 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 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. And because floor polishes are so inexpensive - about $15-$18 per gallon - and easy to apply, there is really no good reason not to use one. Given their complex formulations, though, it is imperative always to test a prospective polish on a small area of the concrete sealer for compatibility before doing an entire floor, and then to follow the manufacturer’s application instructions as closely as possible.