Great question and thank you for writing to us! It’s best to sand with 220 grit sandpaper and add another clear flood coat. Dimples and low spots are caused in a few different ways. Be sure you're using the 1/8" square notch trowel because sometimes if the trowel is not used or the epoxy is not thick enough it won't have enough material to level. You need to have 3 oz of mixed epoxy per square foot for your clear flood coats and color coats. Be sure to let the paint under the epoxy fully dry before applying epoxy. If you had a fan or heating and air from your HVAC blowing in the room, it could cause dimples. Additionally, not torching enough could cause dimples. We sweep across the surface 3 times. We do one from the start of the countertop to the endpoint of the countertop, then we immediately do a second sweeping of the surface, and finally, a third time torching. What happens is that the air escapes and then more comes to the surface; if you torch sweep it three drying curing times it allows time for the new trapped air to make its way to the surface. If the air remains in the surface, it'll come out as the epoxy is curing and not settle back to level because it's too long into the working time. Does this make sense? It could also be from having dust get into the surface as it's drying. Another issue could be oil or grease that was left on the top if it wasn't degreased prior to application. It also will not adhere to silicone properly and can leave voids. Wiping down your project with a tack cloth in between coats can leave behind a residue that repels the epoxy as well. Try not to torch the edges of your project as this can heat the epoxy up and cause excess epoxy to be pulled off the top of your project leaving you with not enough on the surface causing these dimples and divots. Do any of these ideas trigger a thought to what might have been the problem on this pour as opposed to the other pours where this didn't happen? Here is a video showing how to thoroughly torch the surface.
Have a wonderful day and give us a call with any questions.