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Summer 1994 - Article 1

From The Lab
Why Proper Dry Time is CRITICAL to Floor Finish Performance

All of us hear talk about proper floor finish dry time. Most of us understand that floor finish performance is greatly enhanced by allowing adequate dry time. But, few people understand why this is so important and what mechanism is at work.

Floor finish contains many independent ingredients such as water, polymer, resin, wax, plasticizer, coalescing agent and defoamer that, when combined together, form a stable, milky liquid emulsion. Once applied to a floor, most of the ingredients evaporate. What does not evaporate and is left on the floor is the N.V.M. "solid" portion of the finish (polymer resin and wax plasticizers.)

For best results, this evaporation process must be complete before another coat is applied. We can best illustrate this through the diagram below.

When a floor finish does not dry thoroughly and is recoated, moisture gets trapped between the coats. A uniform, tightly knit film is never achieved. The results can be graying floors, excessive black marking and scuffing, dirt penetration, sticking furniture and difficult buffing.

Two closely related elements of dry time are coat thickness and relative humidity:

• Thin coats work best with floor finish because they dry quickly and more uniformly. Persons applying floor finish seem to wait about the same time between coats whether they are thick or thin, so thin coats have a big edge here.
  
• Humidity also affects floor finish dry time. Remember, a lot of water must evaporate for a coat of finish to dry. High relative humidity means that the air is saturated with water. This, in turn, means that the water in the floor finish has nowhere to evaporate. Dry times for a finish can take 30 minutes (on average) to two or more hours. This is why we recommend applying floor finish on cooler, less humid summer days or with air-conditioning on.

In conclusion, for best results:

• Four thin coats
• Low humidity

Floor Finish Just Applied	Improperly Formed Film	Properly Formed Film