70 replies to this topic

[Greg T]

Yep....that's the stuff!

Is this powderthe stuff your buying.... Click Here

[evilgecko]

I got a hard one...what would you call aluminium which has been made by slicing up foil in the blender? It had a close look at it a they look like spikey balls...is there a special name for this type of Al?

[Richard H]

Hmm, I don't know, at a guess I'd say 'Useless' .

To make alu flake you need a ball or stamp mill. A blender will not work efficiently at all for this.

[evilgecko]

lol, ok I got a ball mill, so do I just chuck it in with a grinding media harder then aluminium, lets say iron (I'm guessing you can't use lead balls) and leave it on for a few hours to further grind the Al foil. I also heard of a situation when fresh air is exposed to aluminium and the reaction to Al2O3 cause the aluminium to ignite, will the be a problem here?

[Pretty green flames]

Isuggest you buy a block of Al (they sell it buy the pound) in your local hardware shop and file it down so you get small shards or shreds or whatever just file it down.
Cuz i read somewhere that Al foil is not pure Al.
For grinding i suggest Heavy chromed steel balls

[Richard H]

lol, ok I got a ball mill, so do I just chuck it in with a grinding media harder then aluminium, lets say iron (I'm guessing you can't use lead balls) and leave it on for a few hours to further grind the Al foil. I also heard of a situation when fresh air is exposed to aluminium and the reaction to Al2O3 cause the aluminium to ignite, will the be a problem here?

It will take at the very least a few days of milling, maybe upto a couple of weeks depending on desired mesh. There is a danger of a pyrophoric reaction occuring when you open the mill jar, so be sure to stop the mill and open the jar every few hours so a protective oxide coat builds on the aluminium. The other option is to add 1-2% of stearine to the aluminium, which adds extra protection and can help prevent unwanted reactions e.g. between aluminium and nitrates.

[broadsword]

Would it be possible to use rough balls as milling media so the do the hard work for you? so they would be grinding down the aluminium foil rather than just hitting it like a steel ball would? Has Anyone tried it?

[Patrick]

I melted some scrap aluminum in a homemade furnace I made. There was a "crust" on top that was extremely brittle and I threw it into my ball mill. It was all powder when I checked it an hour later. I'd say around 75% passed 325 mesh. Some of the denser stuff I used my sander. Both seemed to light the same, but I sure wish I knew why parts were more brittle .. and how to recreate it. If you overheat Aluminum will it get brittle? If I knew how to make the brittle aluminum that would save a lot of time and mess trying to powder it.

I seperated the aluminum into three mesh groups. 100-200 mesh, 200-325 mesh, and -325 mesh. The 100-200 looked great in a fountain I made, had to test out the home made stuff. The -325 I ball milled for a few more hours.

Overall I was very impressed I could turn an old lawn chair into some nice pyro comps.

I'm hoping to try my hand at some homemade magnalium. Got plenty of scrap aluminum and around 10lbs of scrap magnesium.

[evilgecko]

When people make hammers, don't they cast the shape with the special alloy, then heat up again so it is red hot and then plunge it into cold water, which makes it very strong. It should also make it brittle, but the special alloy prevents that. I'm thinking if you heat aluminium intil its red hot, and then cool it quickly, it would make it brittle?

I gotta few questions for you patrick.
How do you make a homemade furnace? At the moment I'm limited to a camp stove which can just melt lead.
Where is a common place where you can buy mesh? Not like a pyro supplier or anything, but someplace where you could buy it anywhere in the world. So far I've got a kitchen strainer and I'm planing to get a builders siv (the ones that get lumps of concrete out from dirt), so I can seperate my new pressed and corned black powder (lol pressed in a little 1 ton vice)?
Where do you get scrap magnesium? I've got plenty of Al from melted engine blocks and windows frames, but I've never heard of scrap magnesium, I'd thought it would oxidise?

PS. A very expensive way to get premixed magnalium is to grind up the metal German pencil sharpners. They are made with a magnalium alloy, which when heated and put in hot steam, glows bright white and allways carcks the glass tube you have it in (even when its not touching the sides!) Don't use the cheapo 'Made in China''s because they don't work. This magnalium is supirior to dry mixed because it has been melted and 'fused' together

Thanks, Geoff

[Matt]

When people make hammers, don't they cast the shape with the special alloy, then heat up again so it is red hot and then plunge it into cold water, which makes it very strong.

I think youll find they use oil.

-matt

[Arthur Brown]

There are few uses for pure Aluminium that yield us suitable scrap for melting, EXCEPT for electrical cable all mechanical uses need the strength of alloys. Most underground distribution cable is aluminium and for conductivity is 99.99% pure and is VERY soft. Virtually every time there is an electricians hole in the road there will be 25Kilos of cable to waste and usually it will be scrapped for recycling. try local scrapyards.

[Patrick]

I'll start with the Mesh screen. I purchased all mine from http://www.mcmaster.com/ Search for wire woven cloth, and select your grade. Prices are extremely cheap, but not sure on where they all ship to. Mesh screen is used a lot for screening graphics onto clothing. A great place to look would be Ebay. Look for Test sieves. They are used for soil testing and seem to be selling cheap on ebay. 200 mesh sized are very common and they are stackable. A couple common companies are Endcotts or Fisher Scientific.

The furnace I got the idea and the basic plans from http://www.backyardmetalcasting.com/ I took an old metal 5 gallon gas type can and cut the top off. I then made the cement mix, which I didn't follow the instructions.

The instructions call for Portland cement, silica sand, perlite and fireclay. I used a premixed cement and the perlite, which I found at Wal-mart in the home/garden section. "Perlite is a light-weight odorless, sterilized, heat-expanded volcanic mineral. It's used in potting soil to loosen and aerate the soil resulting in strong, branched root development. The reason it's so good for refractory formulas is because it doesn't conduct heat very well (heat doesn't pass through readily). A similar product is called "vermiculite" it's added to potting soil because it retains moisture. This quality makes it undesirable for refractory."

The rest of the construction was really simple. Just had a steel pipe in the bottom for my torch and fill with the refactory mix. The gas can worked nice because the top of the furnace now has a nice handle.

The site contains great information, but I went on my own when building. I already had a propane torch, so mine is propane powered, but the site says bbq charcoal will get hot enough to melt aluminum.

The magnesium ... I found a seller on Ebay that was selling magnesium square tubing and also noticed they had a lot of other metals. I emailed them asking if they had any scrap magnesium, they replied back asking how much I wanted. I think it came to $3.00 a lb including shipping. I only purchased 10lbs, as the making magnulium is new to me. If you know where to look, you should be able to find magnasium. There are a few car parts made out of magnesium, the VW bug complete engine block is magnesium. May be able to get some cheap from a junk yard. I did notice there were different grades of magnesium, but figure they would all have the same affect for pyro.

Now that you mention the aluminum being red hot, I do recall when I was melting my aluminum that it did become red hot. When I dumped the aluminum the brittle stuff was red and I would press it with a hammer to cool it off. It was already brittle before the hammer though. At first I thought it was just dirt that had floated to the top as I couldn't mix the brittle with the molten aluminum. I then took the brittle aluminum sprinkled some over a torch and it brunt bright white, verifying that it was indeed aluminum.

Edited by Patrick, 28 November 2004 - 11:15 AM.

[evilgecko]

I went to McMaster-Carr, man they have alot of different types! I was looking at the Woven Wire Cloth-Standard Grade-Galvanised Steel section. When is says 'openings per square inch', do you multiply the numbers together to get the mesh size...eg 24*24 is 576 mesh?
I'm thinking about ordering some.
The problem with buying magnesium is that I don't think I can get it into New Zealand. I went to the government site and it said they have regulations on any type of magnesium and even powdered aluminium!
Thanks for the info

[RegimentalPyro]

When is says 'openings per square inch', do you multiply the numbers together to get the mesh size...eg 24*24 is 576 mesh?

Not quite. Mesh is openings per inch, so take the square root of openings per square inch to get the mesh.

eg: 24 openings per square inch would be about 5 mesh.

A good cheap source of Magnesium that is unlikely to be regulated can be found down at your local chandlers [boat yard]. Ask for "Sacrificial Magnesium anodes". These are large lumps of fairly pure Magnesium which offer some protection for boat hulls from corrosion. They cost about a tenner [UK pounds] for a couple of Kg's.

NB: They can also be made of Zinc which is of course useless for us. Check it's a *Magnesium* anode.

You'll need to powder it somehow though.......

Edited by RegimentalPyro, 28 November 2004 - 09:28 PM.

[Richard H]

Almost right mate It's important to remember mesh size is given as the number of openings per LINEAR inch.