If you can find it, anhydrous borax is better than the ordinary, the ordinary goes off like a gunshot if you get it on the anvil then belt hot metal over it. It's quite fun but I doubt the 'elves would approve. It's sprinkled on the hot metal, then back in the fire, then sprinkle some more on, bring the pieces together and tap them very gently together. Too hard and they won't stick. And be prepared for a few bangs!