Hardwood Floors December 2017/January 2018

Finally, too thin of coverage can overwork sealers or nish, possibly resulting in bubbles, improper leveling, and other undesirable outcomes. Too heavy of a coat can also cause problems. Aside from extending dry/recoat times, air bubbles from application or shaking, especially if not allowed to “rest” before use, can by the time they work up to the surface, be prevented from popping by a surface lm that has already started to ash, leaving permanent bubbles. is can be exacerbated by On hot summer days, most contractors know to stack the odds in their favor by coating early in the morning or late evening or night. Both are excellent ideas, especially with isocyanate- crosslinked nishes since their reaction rates can double/pot-life can shrink every 10 or so degrees above 75˚F. BLACKOUT In front of windows, the sun can heat up the oor and cause the nish to ash and set up prematurely. Consider hanging black plastic to block the sun. is does not have to be as involved as draping for dust and should be done the day before coating, or long enough before to ensure that the sun has not already heated up the oor areas that it hits. O en, this means only having to drape o only part of a window, also making it easier to use (and reuse). ARE YOU READY? Coat oil-modi ed stain/sealer/ nish when it is ready to coat with waterborne nishes; allowme to explain. Mineral spirits/ Stoddard solvents in oil-based products tend to rise up out of the coating and sit in a layer above the oor, suppressing the evaporation of more solvent. e higher the humidity, the greater the suppression/less the air can hold. Inversely, the colder the temperature, the less the air can hold. Heat can induce more solvent to evaporate since it increases the amount that a given air volume can hold. Extrapolating, then, if a coated space is heated to the limit of application directions, but closed up, it may be days before an oil-based stain/sealer/ nish is ready to be coated with waterborne nishes. is does not mean that the stain or sealer is not behaving how it should; rather, you are not supplying the proper conditions for it to happen quicker. e single best thing you can do to speed up the process is to get new air in and old air out; use fans, heat, windows, etc., to expedite the process. is is something that is be er addressed with the homeowner before doing the job. cooler oor and room temperatures. THE OTHER HOT COATING

DO YOU HAVE PROPER COVERAGE? Coverage rates are an important component of the coalescence, dry and cure equation. Obviously, to match the advertised recoat times, stick to the recommended coverage rates. Again, these will vary some from region to region (as temperature and humidity also vary). Any time that coverage is heavier than recommended, the recoat time will be extended, for both oil-based and waterborne products. Some coatings are a ected more than others. For example, applying oil-based sealers too heavy can result in a dramatic extension of recoat time, by as much as an extra day or two. is is due to the nature of the driers added (metal-based agents that help to dry the coating). Typically, these sealers have a lot of surface drying agents, meaning that they are unable to dry a thicker coating quickly. Oil-based nishes are a ected to a lesser extent since they are generally equipped with surface, mid, and through driers. Predictably, one-component waterbornes are a ected more than polyisocyanate-crosslinked two-components, since they are dependent on oxygen to crosslink them. is makes it easier for a heavy coat to skin over on top too early, slowing down the dry, cure and recoat time of the rest of the coating. Be aware of low spots, as these will naturally accumulate more product/area than in at areas, in some cases the equivalent of several coats of nish. is increased accumulation will dictate the recoat times of the entire oor, so always use low areas to determine when to apply the successive coat. It does not take a genius to gure out that the combination of hot-coating and coating too heavy can extend the coalescence, dry, and cure of a coating system even further. A heavier coating makes it even more di cult for oxygen to get in and solvent to get out of a coating system. If every coat in a three-coat system is applied heavy, the cumulative e ect may be as if a fourth coat was applied.

Photo courtesy of Charlie Peterson

the magazine of the national wood flooring association

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