Hi - I am searching for a suitable matt black paint to coat a thick glass fireplace hearth that will be sitting underneath a woodburner. I have used a Rust-Oleum all-purpose paint previously, but am cautious about the fire safety angle (NB the wood burner is on legs, the hearth won't be subject to extreme temperatures). I also need something that I can be confident will stay on glass - can't find much mention of that in product details. Can you recommend a suitable (good value) product please? Thanks!