Brownells Gun Techs and Firearm Myth Super Sleuths (aka "The Smyth Busters") Caleb Savant and Steve Ostrem tackle a tricky question: Is a cold blued finish as good as a traditional hot blued finish? Actually, it's not a tricky question: the answer is NO. The ~290 deg. F. heat of the hot bluing process builds up a layer of black oxide on the surface of the metal that's really quite durable. Hot bluing requires expensive equipment and takes some time and experience to get it right. Cold bluing is applied at room temperature and isn't nearly as durable as a hot blued finish. It's a chemical reaction just on the surface of the steel, and as a result, cold blued finishes wear off pretty easily. Cold blue is really meant for touching up nicks and dings, and not for finishing an entire firearm. Some folks do finish whole guns with cold blue, but it's more difficult to apply evenly than hot blue. And that finish won't last as early long as a traditional hot blue. Good-quality cold blues like Oxpho-Blue®, Formula 44/40®, and Dicropan T-4® from Brownells are great for touching up those small nicks and scratches to protect the bare metal AND blend in with the existing bluing so you DON'T have to re-blue the whole gun.
