[Grumples]

I want to use thermite as a (relatively) simple way of getting molten iron, which I then plan on casting into various shapes.  I know that this is feasible, but I am worried about the practicality.  I know that Theodore Gray (of Popular Science fame), one of my favorite mad scientists, has done this before; and, from looking on the web, I'm pretty sure that he wasn't the first.  
  Why thermite? To me, it seemed like the easiest means of getting molten iron.  From what I have read about it, it doesn't pose that much more of a danger than the liquid iron itself would, except for the sparks that the reaction produces, which could rather easily be contained.  Of course, the intense heat itself can cause problems if not treated properly.
  How? This is the real problem for me.  Basically, my plan would be to light the thermite in a graphite crucible with a hole in the bottom that would be covered by something that would hold in the reactants, but would be melted during the reaction, thus allowing the iron to pour out into a mold underneath it. The entire apparatus would be contained in some sort of "box" (probably made out of bricks, cinder blocks, and/or scrap metal) to contain sparks or spatters.  In reading about Theodore Gray's attempts, it seems like a rather touchy substance: simply by using a penny to cover the hole, he caused an explosion by the sublimation of zinc from the penny.  Another problem I would have is making a mold.  What sort of substances would be able to take such high temperatures?  Graphite is the first thing that comes to mind, but it does present problems.  I'll be using it for the crucible, but making a mold out of it would be very difficult without sophisticated machine tools, and somewhat expensive, large, and heavy hunks of graphite.  Ideally, I would like something like clay that I could easily turn into a mold.  I thought of concrete, but I'm afraid that the trace amounts of water in the concrete might vaporize; causing gas pressure and potentially spattering or an explosion.  I also thought about fire clay, but I can't seem to find any relevant information (or suppliers) for it.  
   Finally, does anybody know about the legal repercussions of this?  I've looked at several web pages of people who have conducted this experiment, (obviously not the best source of information, but some of them, such as Theodore Grey's (www.periodictabletable.com) are pretty reliable) and none of them so far have said anything about the legality of it.  In some of them (such as this one: http://www.allatoms.com/thermite2001/thermite2001.htm) you can clearly see the guy just putting a crucible full of thermite in the middle of a field, lighting it, and running away.  In a relatively old article on this site, someone mentions that ATF considers thermite to be a high explosive (because of the aluminum).  In the somewhat large quantities I am thinking about (enough to fill the mold, so maybe around a pound or so, depending on the mold), I doubt something like this would go undetected; not that I would do this without making sure it was legal, first.
  Can anyone tell me what they think about this?  Materials I could use, safety rules I should follow, etc?  I want to get as much feedback from knowledgeable people as possible before I attempt to do this.

[Torus]

As long as u keep it contained im shure it will be fine, but where do u plan to do this?

[Grumples]

I'm not sure where geographically, but probably somewhere like a parking lot; certainly not indoors.

[hmx9123]

This is going to be a somewhat sticky topic, as we really don't want people going over how to make thermite, etc., but handing out safety information is at least reasonable.

You should be aware that without a manufacturing license from the ATF you can spend a long, long time in prison in the US if you are caught with this material.  At the current time, the ATF is cracking down on the amateur pyrotechnics field, too, so beware of the authorities.  To be legal, you need a Low Explosives Users Permit, a Low Explosives Manufacturing license and the HEUP and HEML if thermite is considered a HE (not sure if it is or not).  Then you need to get your state licenses, have storage facilities, regular inspections, and a permit and permission of the local fire marshall.  Good luck with that.

Aside from the legal implications, I've seen this reaction done a number of times, both indoors and out.  It used to be done in the lecture hall at my undergrad university.  They would run it on an incredible 80g scale indoors (there is a TON of smoke).  Apparently, they used to run it on 300g indoors, but I saw the video of it catching the projector screen behind the reaction on fire, so they quit doing that.  I would definitely NOT advise doing this reaction indoors.  You should do it on a pile of sand or dirt.  It can damage asphalt.  Make sure you have anything flammable away.  Run it on small scale if you've never seen it before (1-5g).  Do NOT try the mold trick first.  Run it on small scale in an open pan, then run it on a larger scale, and then, only when you feel comfortable with it, try the mold idea.  Cast iron molds, stainless steel molds and POSSIBLY a fire clay mold may be OK.  The clays I've seen have always broken when thermite is run in them.  As for covering the hole, just place a piece of paper over it.  it'll burn away.

The official demo I have of this says that sparks can be thrown 16' vertically and 20' laterally, and although I have never seen this myself, I would consider it the minimum safe distance both for people and flammable materials.  Obvisouly make sure you're wearing safety glasses, etc.  Something else people not in the pyro hobby don't know: wear only cotton or wool clothing.  Polymers, if caught on fire or heated too much, melt and stick to your skin as they burn.  It's a lot better just to get burned.

So, the official position of the site is that you shouldn't be doing this because it is dangerous and you could easily injure yourself. (And we don't want to get sued).

[jdurg]

A thermite would probably be considered an incindiary(sp?) device and not an explosive since there is no formation of gas, so therefore there is technically no ability to 'explode'.  (An explosion requires the formation of a gas).

[Corvettaholic]

I remember looking up the classification of thermite when I first joined this site, and I had some nut-job idea of making a blast furnace with the stuff. It is considered incendiary and not high explosive.

[hmx9123]

I hadn't checked the ATF's website for the definition of Thermite.  I realize it is an incendiary, although production of gas has nothing to do with the ATF's classification.  Their classifications are generally arbitrary.  One big thing that confuses everyone is that they consider flash powder, or any firework that contains over 50mg (or 125mg for an aerial shell) to be a high explosive.  That's fine that they classify it that way legally, but people start thinking that flash is a HE, and there's lots of confusion about it.  Tons of debate goes on about that because of the classification there.  You also have to wonder about their classifications--they considered a Duraflame log for firestarting to be a 'dangerous pyrotechnic device' in a recent court case.  So it's just word to the wise: be wary.

[Grumples]

Bummer.  I figure this is like drug laws: if you try it in small quantities, you'll probably get away with it.  Try something big, and you're probably screwed. I'm very wary of doing this experiment, especially considering where I live (Washington DC, a block away from our good friend Donald Rumsfeld, a.k.a. Big Brother), and the quanities I would need.

[hmx9123]

You know, thermite will leave a mess of crap, too.  The iron you get from it is going to be dirty.  If you want iron to pour into a mould, take a look at internet resources for building your own furnace/forge.  You can actually forge your own stuff, and it's legal.  For one example, here's a guy that is making his own woodcarving knife with his own furnace:

http://www.primitivearcher.com/articles/drawknif.html

Good luck.

[Corvettaholic]

I don't know if this will be useful or not for you, but I went ahead and dug up my very first post to the forum on guess what? Thermite furnace.

http://www.chemicalforums.com/index.php?board=9;action=display;threadid=187;start=msg944#msg944

I had some nutty idea of doing something cool with it, but I really, really, really wouldn't tangle with the ATF if I were you. I met some girl at a bar once, and she worked for the ATF and told me all about how they work. Don't make thermite.

[Grumples]

Corvettaholic, I read your old thread- it is what brought me to this web site in the first place.  On another note, thanks for the link, hmx.  I'll check it out.

[billnotgatez]

I am planning a future experiment, which requires thermite to prove or disprove a hypothesis. We have a source that has been previously listed that legally supplies small quantities of thermite and ships it. They also suggest using ribbon of magnesium as a fuse. I have discussed this with a PHD person who has lots of experience and we both agree that I need to take extreme measures to insure safety.
Here are some of the initial thoughts. An open container procedure that is resistant to burn through will be devised. Doing the experiment in an open area far away from the others. Knowing that extinguishing the fire is near impossible. I will create a way to view the burning indirectly, like a remote camera. I am still mulling over the experiment to think up more safety measures.

Needless to say working with thermite is not to be taken lightly, even if you are doing it on a small scale.

Regards,
Bill

[spark]

I have a similar interest in thermite.  As a small run molten iron producer, it beats heck out of setting up the furnace to supply the heat to melt iron externally.  I just tried lighting aluminum filings with a magnesium sparkler and came just short of a sustained Al to AlxOx reaction.  My guess is that the thermite reaction requires the same starting temp (that to cause self-sustaining burning of aluminum.  The most frequently given starting method has been mag ribbon in mixture, or mag ribbion in mag powder in mixture.

Additionally, I remember some info from highschool Chem class LONG ago, when thermite wasn't considered by a hysterical populace to be a terrorist weapon.  1) Thermite has been successfully used to produce durable welds where arc and gas welding is impossible, such as butt plate welding for warshop hulls, and repair of same.  Thermite produces aluminum oxide and reduced iron.  If the ingredients are clean, the iron will be clean.  2) The proper container for a thermite reaction is a paper cone cup, such as snowcones are sold in.  Thermite will melt or otherwise decompose ANYTHING it burns in, so a disposable container which burns cleanly is the best way to go.  Put the paper cone in a ring stand, put the thermite in the cone, top with a small mound of magnesium powder, fuse with magnesium ribbon (will ONLY light with propane torch or higher heat...), light it and LEAVE.

I only guess, having not heard an explanation, but it looks like the thermite burns down the center and outward, carbonizing the paper which mold releases the ring stand, and liquid iron (plus alumina: aluminum oxide) drips out of the bottom of the cone, insulated by not yet burned thermite mix surrounding it.  It should get pretty vigourous as the reaction spreads outward in the misture: I'd arrange for spark shields, like galvanized roofing arranged to deflect sparks downward.  The tremendous weight disparity between alumina and iron should cause the aluminum oxide to float in the top of the sprue, never entering the mold proper.

Thermite will 'china syndrome' until the heat in the iron is disbursed, glassing sand, melting iron, igniting most non-ferrous metals, exploding concrete.  Therefore use cope and drag molding with green sand and initiate the reaction directly over the mold's sprue hole.  The same rules and directions for cast iron sand casting should apply to thermite, but remember, there is heat in thermite beyond what is required to melt iron.  Green sand casting has the advantage of having been designed specifically to disburse heat by steam generation without causing explosive pressure buildup.

Have seen the ratio of Fe3O2 (black iron rust) to Al to be 8 to 2 by weight, and also as 2.888 to 1 (which agrees...) from another source.  I imagine that a reactionary and ignorant authority can outlaw anything, but you can build a better bomb with kerosene than you can make with thermite, so what would the point of outlawing it be?

In closing, be careful be careful be careful.  Make sure your entire experiment is over a sand pit (not anything flamable, not concrete, not metal).  Don't involve any apparatus you can't afford to lose, and most important, don't be there when the reaction occurs.  Be around a corner with a mirror if you MUST watch.  Without having seen it, my guess is that the light from thermite is probably eye destructive, let alone sparks, etc.  Do it on your own property.  More people are arrested for where they did something than for what they did...  High energy radiation of any kind from any source is potentially carcenogenic.  And because some say that this reaction sprays sparks, use deflectors to prevent brush fires...  Good luck.

[hmx9123]

Thermite needs the aluminum in it to melt before it gets started in most cases, so you need some sustained heat for that.  Once that occurs, the reaction begins and proceeds quickly.  

Spark: it doesn't sound like you've seen or done this reaction before.  That's not a problem, but if it is the case, it might be wise to explicitly state so at the beginning of the post, as the rest reads as if you've seen/done it before.

As with anything on the internet, these posts could all just be garbage, so if anyone is planning on doing anything dangerous (thermite in this case), you'd be wise to look up an original source somewhere.  There should be mounds of information on this at the library.

Thermite was used for years to weld railroad tracks together.

It is also known at the 'Goldschmidt Process', and is found as such in some older literature.