Bubbles
and Craters
The Problem:
Topcoat has bumps when dry.
The Cause:
Bubbles:
This can be the result of the finish or the floor being too
cold, humidity too high or the previous coat(s) not being dry
before this last coat was applied. In addition, not following
the coverage rate directions such as, applying too heavy a coat,
often lead to this condition. Most finishes cure from the top
down. If, the wet coat forms a skin before the air folded into
it can escape, the finish forms bubbles and can not level out.
Craters:
Bubbles that have released their air but the finish has then
hardened to a point that it can not level out and feels rough
to the touch.
Trash in the Finish:
Airborne dust from heating vents, failure to tack efficiently
place dust particles in the finish, which look like bubbles
until seen under high magnification.
How to fix the problem:
Oil Modified bubbles and craters can usually be screened and
re-coated with a thin coat of finish. Water base finishes that
have bubbled can be scraped flat but will probably require re-sanding.
How to avoid in the future:
Determining the conditions at the job site and ensuring it is
feasible to apply the finish is the responsibility professional
sand and finishers. Tools such as hygrometers and moisture meters
tell you what the job site conditions are so you can act accordingly.
Where possible alter the temperature, humidity and ventilation
conditions to those recommended by the specific product directions.
Block off all air vents, sweep, vacuum, and tack then apply
finish.
If this is not possible to do immediately, it is better to wait
until you can.
