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Making Magnalium

Magnalium, as it's name suggests is an alloy of magnesum and aluminium. It's found a lot of use in fireworks in recent years. It is not so reactive and likely to corrode as pure magnesium. It's quite hard to get hold of, but after a few experiments, I've found it's not too hard to make

Here are some chunks I made.

Aluminium can be found in scrap sheet, old pully wheels etc. or if you can't find this, it can be bought in sheet or rod form - this is the expensive option though! If you are using scrap, make sure it is aluminium, as a lot of castings are made of zinc alloy (Mazak) which won't do! If you snap it, zinc tends to break with a crystaline surface and aluminium tends to bend.

Magnesium is harder to get hold of, but is used to protect the hull of steel boats in the form of a 'sacrificial anode'. These can be obtained from a good ships chandler or on the web. This is one I have cut a chunk off with a hacksaw. You have to discard the steel mounting strip.
The hardest bit is getting enough heat to melt the aluminium. I used a propane torch, put the bits in an old tin can and packed it with firebrick to stop the heat escaping. Keep a steel rod at hand to stir it about a bit.

SAFETY WARNING. You are dealing with very hot metal here. Apart from the possible danger of it catching fire, it is very easy to burn yourself with hot metal, hot tools or the flame you use to heat it. Wear gloves, keep all the stuff away from anything else that might take fire and BE CAREFUL!

When it's melted and properly liquid, drop in the magnesium. I used equal weight of both metals. This is the bit where it might catch fire! I've been told that if it does, scattering a little powdered sulphur on top will put it out, so keep some at hand. I had no trouble, just a few flashes on the surface. I think the trick is not to make it hotter than you need in order to melt it. Stir again, and as soon as the magnesium has melted and mixed, remove the heat and cover with a scrap of metal sheet to keep the air out a bit. I gave the tin the odd shake as it cooled to encourage it to crystalise a bit. When its cold, strip off the tin with tinsnips and you will get a metal disk like this.

I thought that powdering the metal would be a major problem, but it is as brittle as glass! A few whacks with a hammer on a metal plate soon reduces it to chunks and then to powder. Hand and eye protection are a good idea here, as the shards are very sharp and fly about everywhere.

Here is the result of a bit more hammering. You can then sieve the material. Larger (10 mesh) bits produce sparks (but not in my experience the 'sizzling noise' described by Ron Lancaster). It's best use is at about 80 mesh to make crackling microstars with either lead or bismuth oxide. When added to a fountain fix, these produce loud pops and bangs, accompanied by a bright flash.