Acid-Stained Concrete: Why Use A Floor Finish?
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 almost immediately and 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 for using 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 throughout major metropolitan areas, that serve as a visible deterrent to the continuedgrowth in use of this flooring application.
There are numerous, worthwhile and essential benefits from using a floor polish that cannot be derived through a concrete sealer 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 don’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) easy "buffability" to restore gloss; and 9) ease in stripping and replacing. In short, 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 by the industry, as a “sacrificial layer”.
The clear sealer is just as important to acid stained concrete flooring ,but is meant to be more of a “permanent”, protective layer. Consequently, its 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 design and floor color from harsh 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 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 their composition. Sealers are entirely composed of a resin or polymer, such as an 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 floor polish benefits outlined above. This wax also makes the formulation of floor polish much more complex, and therefore 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 manner becomes critical. Specifically, floor polishes almost 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.
Because floor polishes are more complex, manufacturers also 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) 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.
One great benefit of floor polish that few 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 and residential environments, but the high light refraction associated with gloss sealers can be bothersome to people in medical and institutional surroundings, and simply unappealing to owners interested in a "warehouse" lool floor. Using two or more coats of a “matte”, or even “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 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 considerably in gloss from one brand to another.
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 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, making a sealer more brittle. This can lead to flaking and delamination of the sealer, a common problem with stained concrete floors. "Brittleness" is not a problem with floor polishes because the wax component 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 with 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 over the past year. 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 polishes, where gloss finishes are suitable, but they no longer carry a matte floor finish. 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-$18 per gallon), and easy to apply, there is really no good 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.