Floor Finishes Newsletter

Have you ever applied finish to a hardwood floor and the result was a flat, dull floor with a low sheen look or had a floor that took a week to dry? If you have, it could possibly be because of the sanding grit paper you used. A lot of contractors will sand a floor starting out with a 36 grit or a 40 grit paper, depending on the over wood, then jump to an 80 grit paper and finish out the floor with an 80, 100, or 120 grit screen. This system creates an irregular sand cut on the surface of the wood causing them to use more finish per coat, giving the floor that dull look, and slowing down the dry time because the finish is thicker in the deeper cuts which were not sanded out by the finer grit paper. Each sanding cut is designed to remove the previous cut, helping the finish set up on the floor better, giving you a more finished look, dry more consistently, and saving you money because less finish needs to be used. It is normally recommended that only one grade of sand paper be skipped in a sequence, such as 36 grit, 50 grit, 80 grit, or 40 grit, 60 grit, 100 grit. This sanding system may add more time to the job, but what are a few more minutes on a job if it will keep you from having problems and going back on the job to repair them? Try this system on your next floor and see the difference!

FINISHING TIPS

Climates and Conditions that Affect Dry Time

Ideal conditions for floor finishing are 65 - 75 degrees (F), 45% - 60% relative humidity with minimal air flow. Best results will be achieved when the air, floor and finish temperatures are all the same. Unfortunately, we rarely have ideal conditions. Each type of weather and/or conditions affects the way the products work in different ways. Consider the following:

Hot Dry>80° F <40%

Hot dry conditions will create fastest drying situation for floor finishes of any type. Coat early in the morning or after the sunset and/or use a retarder. Limit air movement. (Dry slows MCU)

Hot Damp >80° F >60%

Hot damp is not as severe as hot and dry since the dampness (humidity) will slow solvent or water evaporation therefore slowing dry. Some indirect air flow will aid drying. (This causes fast dry for MCU - add retarder and limit air flow)

Sun on Floor-Hot Floor

Hot floors or hot spots on any floor will cause the finish to set up quickly. The natural tendency in these spots is to apply the finish heavier which may cause the final finish to appear uneven or orange-peeled. Either coat floor before or after the sun heats the floor.

Warm Finish >Temperature of the Floor it is Applied to

Warm finish applied to a cool or cold floor will flow and level quite nicely but will usually result in a thinner final finish appearance since the finish will go much further than expected. If the floor is too cold the finish may not dry as intended.

Heavy Coats >30% heavier than Manufacturer Recommends

Heavy coats can be misleading since they will almost always bring better flows and leveling of the finish. Since most coatings are designed to be applied in thin films, heavy coats could negatively affect the curing and/or the durability of the final coat. Each coat will require additional dry time and subsequent coats could crawl or wrinkle.

Cold Dry <60° F <40%

Cold temperatures will slow the dry and cure of most finishes but can most severely impact waterborne finishes. The film formation can be impaired if the temperature gets too cold. (<40°).

Cold Damp <60° F >60%

Same as Cold Dry except the dampness can severely affect the dry of solvent products like OMU or oil stains

Air Movement - Direct Air Flow

Direct air movement across any finish will result in faster set up of the coating. This will usually show up as lap marks, uneven flow and leveling or as an orange-peel appearance.

Rain or Fog >90% Humidity

Rain or fog will slow the dry of all finishes. Allowing indirect air flow (air exchange) will aid drying time.

Additives

Additives such as hardener, crosslinker or retarder all contain some solvent and when added to hot or cold finish can cause the finish to react in different ways. Any of these added to cold finish will appear cloudy and not readily mixed in. Crosslinker added to hot waterborne finish can shock the finish resulting in a stringy, gelled appearance which will not strain out.

Cold Finish <Temperature of the Floor it is Applied to

Cold finish applied to a warm or hot floor will go on heavy and dry with an uneven appearance or sheen. It will be harder than usual to apply and because the portion of the film that contacts the warm surface will set quickly and the heavier film above will set slowly, the integrity of the finish may be questionable and slow to cure.