Have any of you guys used muriatic acid to etch blades? I have a blade soaking in it for the past hour. I've been checking on it but it isn't doing much. It just turned grey but very slowly. I am wondering if it is because the container is probably 20+ years old or if muriatic acid just isn't good for etching blades. I was hoping it would work out because I have a 5gallon pail that someone left behind when I bought a house a few years ago. The pail is unopened. The blade is O-1.