 |
Second-Coat Adhesion Problems
With Varathane Oil-Based Urethane Floor Finish
|
In
This Article:
Discussion of urethane
adhesion problem and solutions. |
Related
Articles:
|
Skill Level:
2-3 (Basic to Intermediate) |
Time Taken:
About 3 Hours |
By
Bruce W. Maki,
Editor
When I applied the second coat of urethane on a floor refinishing
project, the wool applicator seemed to drag a bit, and the finish
seemed to have more "brush" strokes than normal. Later
that day, when the second coat had dried, I noticed that the
finish was terribly rough.
Upon closer inspection I could see a wrinkled
appearance to the surface of the urethane.
Almost the entire 400 square feet of hardwood floor
had this wrinkled texture. |
 |
|
 |
Note the cloudy or milky appearance.
This is an indicator of urethane that has failed
to adhere to the surface below. |
|
Some of the wrinkled areas had
considerable cloudiness. |
 |
|
I called the customer service number listed on the can
(1-800-635-3286) and spoke with a man who was immediately familiar
with this wrinkled finish. He explained that the humid weather we've
been having was the root cause of these wrinkles.
The weather was cool but quite humid when I applied the first
coat of Varathane. The next afternoon I scuff-sanded the first coat
and applied a second coat. Apparently the first coat had not fully
dried and was only dry on the surface. The Varathane tech rep said
that in humid conditions it can take 2 or 3 times as long to
fully dry.
Under normal humidity levels, Varathane will be fully dry within
12 hours. I didn't give the first coat any more than 18 hours to
dry, when in reality 36 hours would have been better.
The Remedy:
 |
I tried scraping the floor with a carbide
paint scraper. The urethane scraped up easily. I guess
it wasn't sticking terribly well. |
|
After about 45 minutes of scraping, I had
removed the entire second coat of urethane from an 11' x
12' room.
Problem solved. I swept up the urethane shavings and
dumped them in the kitchen trash can. |
 |
|
Then the story really gets
interesting. It was about 1:00 in the afternoon when
I finished scraping the first room. Around 7:00 pm the
situation started to stink. There was a powerful odor
coming from the kitchen trash can.
 |
It turns out that the pile of
scrapings had begun to spontaneously burn. The
temperature was 360 degrees F on my infrared
thermometer.
|
|
|
 |
After the floor was scraped, it had a dull
appearance.
You can see some spots that my scraper missed. It's
easiest just to sand these down.
|
|
After another day of drying, (just to be
absolutely sure) I sanded the floor with a random
orbital sander and 120 grit sandpaper. |
 |
|
 |
I didn't scrape the urethane from this
narrow strip of floor. I decided to experiment on this
useless part of the room. I used a pole sander on the
back half, and a random orbital sander on the front
half.
I wanted to see how well the next coats of urethane
adhered to the wrinkled second coat.
It seemed to stick quite well, but I question the
long-term adhesion. |
|
This does make me wonder if scraping the bad second coat was
really necessary. Of course, I did this sanding experiment the day
after I scraped the first room, so everything had time to cure
better.
The random orbital sanding took a long time to remove the visible
whitish/cloudy spots... probably more time than scraping and then
sanding.
The hand-sanded section is the real experiment, because most of
the bad second coat stayed on.
No Wrinkles:
After the real second coat, the finish looked
normal and smooth. |
 |
|
Then I continued and applied a third and fourth coat.
Click here to
read more about applying urethane.
More Info:
|
Tools
Used:
- Carbide-Edged
Paint Scraper
- 5"
Random Orbital Sander
- Basic
Cleaning Tools
|
Materials
Used:
- 5"
Sanding Discs, 120 Grit
|
|
|
|
|
Related
Articles:
|
Web
Links:
|
|
|
|
|
|
|
|
|
|
|