A Dirty Coat of Finish

Can you apply the perfect coat of finish?

The Oxford dictionary defines “perfect” as something completely free from faults or defects, or as close to such a condition as possible. “Perfect” in the wood floor finish world means a coat of finish with no streaks or lap-lines, consistent mil-film thickness, consistent sheen, and no debris in the coat.

Any time we are tasked with applying a coat of finish to a floor, perfection should be our target. The problem is perfection may mean different things to different parties. And when the party is a customer who compares the final coat of wood floor finish to the finish on their furniture, there is often a disagreement about what is and is not considered acceptable.

So what is acceptable?

To discuss what would be considered acceptable, we must first identify the culprit, which is “debris.”
Debris in the final coat of finish (as defined in NWFA technical publication, Problems, Causes, and Cures) is a raised bump in the film of finish, often consisting of dust, hair, applicator fibers, foreign contaminates, solid finish particles, or other artifacts.

If we are able to identify what debris in a final coat of finish is, at what point can we determine how much debris is considered to be acceptable versus unacceptable?

  • Ask a homeowner how much debris they would like in their newly coated floor. They likely will answer, “None.”
  • Ask a finish manufacturer how much debris is acceptable in their products. They likely will answer, “We don’t make our finish with debris in it.”

Since the homeowner doesn’t want debris in their finish, the manufacturer doesn’t make their finish with debris in it, and we certainly don’t want to apply a dirty coat of finish, how do we achieve perfection?

In order to apply a “perfect” coat of finish, the following steps are laid out in detail in the NWFA Sand and Finish Guidelines:

  1. Be cognizant of any extreme jobsite conditions that could affect the application or drying of the finish. These conditions may include other trades, inaccessible or inoperable HVAC systems, ceiling fans, water leaks, contaminates, airborne debris, unsecured jobsite, exterior weather conditions, or large windows.
  2. Secure the jobsite to minimize or completely alleviate all foot traffic from the workspace.
  3. Control the temperature at the jobsite. This includes the temperature of the finish, the airspace, and the floor.
  4. Shut off all airflow at the jobsite during finish application. (Keep your fingers crossed that the HVAC system doesn’t kick-on and blow dog fur and dust from deep within the ducts all over your finish.)
  5. Set up a staging area to place tools, finishes, and other items necessary for the job. This staging area should be directly accessible to the floor being coated, which will minimize foreign contaminants from being tracked across the floor from outside.
  6. Thoroughly vacuum any dust from the vents, baseboards, windows, sills, doors, and door frames. Clean from the highest surface to the lowest. Use a cloth where appropriate on all surfaces where necessary.
  7. Vacuum yourself. Clean your shoes (or get your coating shoes on), vacuum your pants, shirt, and hat.
  8. Thoroughly vacuum and tack the entire floor. Re-tack the floor several times, until there is no dust remaining.
  9. Clean your applicator. Whether new or used, an applicator can be the source of debris if not cleaned properly. When cleaning and reusing applicator covers, be sure to use the manufacturer-recommended cleaning procedures and products.
  10. Once the jobsite is secured and you are confident the floor and surrounding area is as clean as it can get, application of the finish should be exactly as the finish manufacturer details in their instructions. This includes preparation, mixing, application method, spread-rates, and dry times.
  11. After the finish has tacked-over, ensure the HVAC system is operating to maintain “normal living conditions.”

When following this process, you will be doing just about everything you can to minimize debris from getting into the final coat. So how can an industry of professionals who strive for perfection, following these guidelines, still consider some amount of debris to be acceptable in any final coat of finish when the cleanliness of the final coat
is a primary objective?

The primary reason this is unavoidable is because wood floors, by their nature, normally are not installed in a sterile, stagnant environment. Most wood floor finishes need adequate time to flow and level as they are drying. Application of finish in a residential or commercial setting may span hundreds or thousands of square feet with massive amounts of open-air space. Any movement within the space, such as a door opening and closing across the room, can shift the air-pressure, causing dust or hair, that was once resting on a windowsill, to become airborne and ultimately fall to the floor. Airborne dust always will find its way down and onto a clean floor or into a drying coat of finish.

Due to the nature of most coating environments, minimal amounts of debris, within reason, almost always can be expected in a final coat of film-forming finish. This is unavoidable. However, when debris in the final coat of finish is predominant and takes away from the overall appearance (from a standing position, under ambient lighting) of the final coat, it may be considered unacceptable.

When comparing wood flooring finishes to the finishes used on fine furniture and cabinetry, there are even more factors that must be taken into account.

Furniture pieces are much smaller, and the finish application is much more controlled. The coatings used on these pieces are either machine-applied or sprayed-on in spray booths, in controlled environments. The finishes are often dried instantly by UV or LED lighting, and are less exposed to airborne contaminants.

The finishes that normally are used for these pieces also are capable of being worked, or rubbed-out, after it has dried. This allows the mechanic to adjust the sheen and remove any imperfections.

Finishes used on fine furniture are not designed to be walked on, whereas the finishes used for wood flooring are designed for heavy use. They are designed to withstand pets, kids, and everyday life. We don’t walk on kitchen tables (normally).

In this profession, you must be a perfectionist at one level or another. To find a bit of debris in the final coat of a film-forming finish is normal and shouldn’t take away from the perfection we all strive for on each and every floor. The challenge is ensuring the customer understands the craft, and the value of getting a handmade, site-finished, one-of-a-kind, wood floor.

Brett Miller is the vice president of technical standards, training, and certification for the National Wood Flooring Association. He can be reached at brett.miller@nwfa.org.

2 thoughts

  1. Great article Brett. One thing I always taught my guys was the DAM rule; Dirt Always Migrates. If you leave dust on the window sill, some of it will invariably end up in the finish when you disturb the air during finish application. This is one area where it’s ok to over-think the problem, because every effort you make to keep debris out of the finish will help get you closer to the perfect coat. When we switched to primarily applying penetrating oils vs film finish, I was very relieved to have less concerns about a dirty final coat holding up our paychecks!!

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