Our MirrorCoat (bar or tabletop epoxy) literature mentions a minimum coverage rate of 1.5 fluid ounces of mixed epoxy per square foot. Ignoring substrate absorption this makes a film about 0.020 inches (20 mils) thick. Dry paint film is typically 2 mils thick. So why do we recommend that MirrorCoat be ten times thicker?
The reason is that a film of MirrorCoat epoxy must be thick enough so that proper flow and leveling occur. Gravity helps thick films overcome surface tension effects that predominate in thinner films. If you brush MirrorCoat on a substrate you are apt to get brush mark "highs and lows" in the cured coating when the film thickness is less than 20 mils.
So, the minimum amount of MirrorCoat you should use is 1.5 fluid ounces per square foot. Add about ten percent more to do the seal coat. If you are coating a bar top 2.5 feet wide by 12 feet long you'll need a quart and a half kit (One quart of resin plus one pint of hardener.) Here's the math: 2.5 times 12 equals 30 square feet. 30 times 1.5 fluid ounces equals 45 fluid ounces. One quart equals 32 fluid ounces, one pint equals 16 fluid ounces, and thus, the kit equals 48 fluid ounces, which is within spitting distance of 45 fluid ounces.
So, how much do you need if you are coating the same bar with an eighth of an inch? Well, an eighth inch is 125 mils (1 divided by 8 times 1000). If it takes 48 fluid ounces to do 20 mils then it will take about six times this much to do 125 mils. Six times 48 is 288 fluid ounces. There are 128 fluid ounces in a gallon. Dividing 288 by 128 yields 2.25 gallons - or, 1.5 gallons of resin and .75 gallons of hardener. There is no kit like this. One could get a 1.5-gallon and a three-quart kit and hit it right on the nose. But, the cost of a three-gallon kit is slightly less than this so we'd go for the larger kit.
There is a more accurate way to figure this: 30 square feet times 144 (square inches/square foot) times 0.125 inches (1/8 inch thick) equals a required volume of 540 cubic inches. There are 231 cubic inches in a gallon. Dividing 540 by 231 equals 2.34 gallons - again the three-gallon kit is the right amount to buy especially when the seal coat is added.