Hardwood Floors June/July 2018

AT THE SITE

Water and Oil - a Manufacturer’s Perspective (Continued)

are the slowest to evaporate and influence the “ready-to-coat- with-waterbornes” time the most. Now, consider that mineral spirits, due to their vapor pressure/ proportionally higher molecular weights, concentrate low above the floor as they evaporate. In effect, in a closed room, as they evaporate, they will sit, like a blanket, low above the floor, preventing even more mineral spirits from evaporating. Higher temperatures mean that the air will hold more evaporated mineral spirits, which will allow this blanket to rise higher/expand upward. Colder air depresses the amount that can evaporate, creating a denser, thinner blanket closer to the floor. What happens if the door to the room is opened? Now, you have allowed the blanket to spread out; more of the mineral spirits can evaporate. What if you open some windows and add fans? Okay, you are getting really smart now – you have facilitated air replacement: you have allowed the saturated air to leave, continually replaced by new (un-mineral-spirits-saturated) air. Combined with added heat, this is the fastest way to get an oil-based stained floor ready to coat with water-based finishes. Remember, as manufacturers, we formulate our products for specific, “average” conditions, both stains and finishes; read the back labels. However, as contractors, seldom do you have the luxury of experiencing these optimal conditions. So, pay attention to your seasonal challenges, and be aware of the effects of temperature, humidity, wood moisture level, and air exchange when coating water-based finishes over oil-based stains. Consider the effects of water popping, wood species, and new/ lace-in wood. Educate your builders/homeowners as to your timeline, so you are not forced to compromise the integrity of your finish system, and thereby deliver a finish system that may not live up to the expectations on which you sold them. Finally, as always, call your manufacturer if you need help. Incorporate these ideas and start coating oil-based stained wood floors with water-based finishes when they are ready to coat. Ethan Erickson is a Chemist at Arboritec USA in Greenwood Village, Colorado. He can be reached at ethan.erickson@arboritec.com.

OTHER STEPS THAT YOU CAN TAKE TO GET YOUR STAINED FLOORS READY TO COAT: READTHE LABEL(S) Read the oil-based stain, sealer, or finish back label. It just might be that the label indicates that the stain is ready to coat in X hours with oil-based coatings; don’t assume that it’s okay to coat with water-based coatings in that amount of time unless explicitly stated. If in doubt, call the manufacturer; we want to help you avoid problems – your success is our success, too! Read the waterborne sealer/finish back label, too – the manufacturers may have specific recommendations for coating We all know that (wet) oil and water don’t mix. The key is not to overcoat oil-modified urethanes with waterborne sealers or finishes until enough of the solvent has evaporated to allow a waterborne coating to properly coalesce, adhere, and cure atop it. Usually (but not always), coating too early is evident by a whitish or opaque haze between the stain and the water-based finish system. While this haze will usually go away with time, it is possible that the adhesion of the water-based coating system has been compromised enough that the homeowner might complain of peeling later on, from the field, seams, or both. Further, it can prevent ideal coalescence, adhesion, and general development of the film properties needed to achieve the full durability of the coating system – also resulting in callbacks. MAINTAINPROPER SITE CONDITIONS Mineral spirits, the solvent in oil-based stains, sealers, and finishes, is really a range of different components that evaporate at different rates. This range comes from the nature of how mineral spirits are produced. Mineral spirits, also known as Stoddard solvents, or generically as petroleum distillates, are just that: distillates of petroleum. When a barrel of oil is processed, it is first distilled. A refinery distillation column has numerous levels, called stages, throughout its height. As the oil is heated, the components vaporize, and then condense (distill) on these stages, according to their boiling points/molecular size, fromwhich they are then removed. The heaviest components (biggest molecules) remain at the bottom, and the lightest components condense back into liquid and are removed at the top stages. Octane exits around the top, just above the range of hydrocarbons that typically make up mineral spirits. Mineral spirits are composed of a range of petroleum distillates, with varying evaporation rates; the longest-chain components over oil-based stains and sealers. ALLOWPROPERDRY TIME

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