Mistake #1 - Poor Floor Preparation
This is the most common cause of epoxy floor failures and/or bad finishes. Some contractors (and do-it-yourselfers) underestimate how important it is to prepare the concrete properly. It requires more than just cleaning the concrete with a broom and hose. Epoxy will not adhere well to a smooth surface.
Mistake #2 - Moisture In The Concrete
This mistake typically happens from not properly testing the moisture drive of the concrete. Regardless of its age, all concrete slabs have moisture driving through them. If not properly addressed, prior to coating the floor, moisture has the propensity to drive upward and create bubbles in the finished surface.
Mistake #3 - Stretching Out The Epoxy
If a contractor runs low on material and decides to "stretch out" or "thin" the epoxy to cover the entire floor, it will result in areas with a distinct difference in color and appearance and a much less glossy finish. It also creates a weaker coating.
Mistake #4 - Faulty Mixing Of The Epoxy
There are a lot of problems associated with improper mixing. The most common of these is mixing the two-part system too fast and trapping air in the epoxy. If this happens, there is a real good chance there will be bubbles in the finished surface after application.
Mistake #5 - Humidity or Temperature Restrictions
Epoxy applied below the recommended temperatures may not harden and cure properly. If a contractor applies epoxy in high temperatures, the pot life may be reduced by half (or more), making the mixture unworkable during application. High temperatures can also create bubbles from outgassing.