I don't use paint anymore. I developed a method that works every time, sign ready to hang in 24 hours, (or less if you want to push it) I use epoxy resin, particularly PB Resin from Coastal Enterprises. Once you go epoxy you'll never go back because the slight increase in cost is offset by total time to apply. I just did a 45 inch by 48 inch sign this morning. It had a large aluminum panel for changeable copy so the smalted area was only around 7 square feet. I used 16 ounces of epoxy with the appropriate color of One Shot mixed in to match the smalts color, in this case Ivory One Shot for light tan smalts, I used 7 pounds of smalt but will recover at least a pound or two when I shake off the excess and with two of us it was done in 25 minutes. I apply the epoxy with a needle nose tip squeeze bottle. I run the tip quickly around the letter and border edges then squeeze some beads of epoxy about an inch apart all over. Then take a cheap brush, you might need a small one for getting between letters, and spread the epoxy all over until it covers your entire background. PB resin will last over an hour during application if it isn't in a huge batch so if I'm doing a 4x8 I will split the epoxy into several bottles to keep it from getting hot and setting up too quickly. The bigger the volume and the longer it sits in the bottle, the faster it will set up. I then shake out the smalts out of small cups or like today I had one pound bags, I just cut off a corner and poured out in a sweeping motion. I lay it on thick to make sure it covers all the epoxy because the next day I flip the sign and pour off the excess smalts onto some paper to recover it for the next job. After shaking out the smalts, with a latex gloved hand I'll gently pat the smalts to make sure it's pushed into the epoxy. PB Resin comes to full cure in 24 hours, but if you really need to push it I'm sure it's firm enough in 12 to 18 hours. Give the back a few wacks when you remove the excess smalts to knock all the loose stuff off. If you are near a Precision Board dealer they should stock the resin. It makes a good bonding epoxy as well for wood, HDU, and anything else that normal epoxy works on. Precision Board has how 2 videos on it but their coverage ratio is way out of wack. I use about 2.25 ounces per square foot of sign which includes letters.
