Hi Bill. Rust-Oleum EpoxyShield Professional should be applied with a 3/8 roller. Only coatings with a solids content of over 90% are capable of being applied with a squeegee and then back rolled.

Hi Bryant. If you sand to knock down the bubble edges, high spots, etc., a second coat of the same product (100% solids epoxy) should completely cover everything up and result in a much smoother surface. This because none of the coating shrinks do to evaporation of non solids content such as water or solvents. What you see wet is what you get dry. Colored polyurethanes are not 100% solids and will react differently. If it is 70% solids for example, 30% of the wet film thickness will evaporate as it cures. If any small holes or craters were exposed from the sanding, they will be exposed / not completely filled as the polyurethane film thickness shrinks 30%.

If I sand the floor and knock down the bubbles, will a second coat mirror the same spots since there was a vapor channel there to create the bubbles in the first place? Some bubbles are little raised spots while others or very small pit.

Could I just as easily put down a colored Polyurethane top coat at this point?

Thanks

OK, so it sounds like we can eliminate trapped air in the epoxy as it was mixed. From your description of the concrete prep, the most likely culprit is moisture vapor transmission. What happens is moisture vapor that is being released from within the concrete gets trapped under the fresh coating. It can create bubbles under the coating as it cures or craters if it escapes as the epoxy is beginning to harden. A lot of water was introduced to the concrete. Etching opens the pores and will allow more moisture to enter the slab. Power washing drives the moisture even deeper. As a result, it can take days for all that moisture to escape – longer if the humidity was up. Assuming that your slab is not below grade (basement, up against a hill, etc.), we are guessing that all the moisture driven into the slab has not had a chance to dry out and escape.

We suggest taping a 16″ square sheet of plastic to a couple areas of the remaining bare concrete. Seal all the edges with tape. Wait 24 hours and then pull the plastic up. If the concrete is dry and the plastic is not wet underneath, the moisture is gone. However, if the concrete turns darker or the plastic is wet, then moisture still exists. The current area that is coated can be fixed with another coat. It will require sanding the surface with 80-grit sandpaper to knock down the crater edges and smooth out the surface. Sweep/vac then wipe it down with denatured alcohol or equivalent applied liberally to microfiber mop pad.

The concrete was etched about a month ago, was thoroughly rinsed(floor was flooded at least three times.) and power washed with last power washing three weeks ago and epoxy applied last evening. Mixing was done with a polypropylene mixer on a battery drill at low speed.