Sciencemadness Discussion Board - Thermite Igniter?

Thermite Igniter?

4s2 - 11-4-2004 at 09:37

I have been trying to get thermite made to study its controllable varriables (for welding and cutting, as seen in my post in the gen chem area) I probably should have posted it here in the 1st place, but I am now.

I made some this weekend and attempted to ignite it with a form of KMnO4 + Glycerin. (when that didnt work I used an oxy/acetylene torch, but it blew/scattered the mixture before it would ignite)

As for the Potassium Permanganate and Glycerin...
What is the propper mixture? actualy better yet, I had assumed that Glycerin(e) was the same base product as glycerol. One chem book shows them as the same thing, but different forumula's, and another shows them as the same thing alltogether. A little googling gets the same contradicting response.
So which is it? or rather which is which? and which is required to ignite thermite?

Or if there is a different ignighter that is known (besides Mg ribbons) that would work.

If the potassium permanganate is the better way to go, aprox how long does it take for the reaction to peak? When I mixed my "clear water" purple fishtank crap that listed KMnO4 as its main ingredient, and a few drops of the glycerin, they just stayed seperated. about 5 min later the purple turned red. thats about it. Is there a way to test to see if its even going to work? (I put it on something combustable at low temps like a paper towel)

What is the temp required to ignite thermite anyway? I have read different things, 300 C, 600 C, 1200 C, etc.

The_Davster - 11-4-2004 at 10:42

Glycerin and glycerol are the same thing, it can be bought at the pharmacy. From your posts in the othe thermite thread I got the impression that your permangante is a solution? It must be a powder mixed with the glycerin that will ignite to catch the thermite.

[Edited on 11-4-2004 by rogue chemist]

BromicAcid - 11-4-2004 at 17:28

When I used to make thermite I mostly worked with cast thermite. Basically this is thermite that has been mixed with some plaster of Paris and water and allowed to harden. I made this in an ice cube tray. Being that they were in block form they held together easily enough to be ignited with a butane torch. I know that these would lead to unacceptable impurities in any welding application but, you could take a piece of wire and put it into each block. When you wanted to ignite your powder thermite you could take a block of it on a string and hold it above the larger thermite charge till it caught, then lower it into it to catch the rest. Thermite reactions are usually none to violent and being that they propagate fairly slowly you should have plenty of time to lower the smaller charge into the main mass and get away before things really start to get hot to the point of danger, as always, experiment on a smaller scale first.

Son of Northern Darkness - 21-4-2004 at 16:08

I'm not sure what temp it is to ignite thermite but it isn't really that hard. Some mixtures that work

KClO3/Sugar
KMnO4/Sugar
KMnO4/Glycerin

Usually a 50/50 mix by volume is good enough.

Sparklers also work.

EDIT: Bromic, holding a lump of thermite by some string and lowering it down, while lit, into more thermite? That's one thing I dont really wanna try.

[Edited on 22-4-2004 by Son of Northern Darkness]

hodges - 21-4-2004 at 17:08

A mixture of approximately equal mass of Al powder and powdered sulfur is easy enough to light with a torch and plenty hot enough to ignite iron thermite. When I was doing my thermite tests I ignited the Al/S mixture using a piece of string soaked in KNO3 solution and allowd to dry. The burn rate was unpredictable, but it always eventually ignited the Al/S.

BromicAcid - 21-4-2004 at 17:20

Quote:

Bromic, holding a lump of thermite by some string and lowering it down, while lit, into more thermite? That's one thing I dont really wanna try.

Well I guess you could put it on the end of a fishing pole if it really scared you that much

Saerynide - 22-4-2004 at 00:32

Wont the fishing pole melt/catch fire?

t_Pyro - 22-4-2004 at 19:16

Not if you're using a titanium wire with your fishing pole...

This is a dead thread.

Hermes_Trismegistus - 22-4-2004 at 20:02

It was crossposted with his other thread.

We found magnesium ribbon cheap and readily availible off ebay, and chemoleo has provided that sparklers will do the trick if you stick one right in the middle of a pile.

Lestat - 1-5-2004 at 17:45

I have never been able to get Mg apart from when I was in school, so I improvise and use lithium from a battery which burns rather well...

Electric Ignition?

Saerynide - 20-1-2005 at 08:13

The tungsten filament in a lightbulb is supposed to reach 2750K. Could a small broken light bulb (those 4.3v ~1cm in diameter ones) with the filament intact ignite thermite when stuck into the mixture? If this works, this would be an awesome electronic igniter

[edit]; Typo

[Edited on 20-1-2005 by Saerynide]

The_Davster - 20-1-2005 at 15:20

I am not sure that would work Saerynide. When electricty is run through the bulb when the glass has been broken off, the filament burns away very quickly. The lightbulb igniter does work with more sensitive powders(like gunpowder) but with thermite, the filament may reach 2750K, but only for a few fractions of a second, so not enough energy would be transfered to the thermite in order for it to catch.

[Edited on 20-1-2005 by rogue chemist]

Quince - 3-2-2005 at 20:32

Use an arc. Sufficient voltage is needed for dielectric breakdown of air (~3 kV/mm), but you need high current to get high temperature. A flash mechanism from a disposable camera can be adapted for this, as it generates a very high voltage pulse to ionize the bulb, and then discharges a capacitor that's only a couple of hundred volts.

A simpler way, however, is the following. Two carbon electrodes (such as those taken from alkaline batteries) are fixed with a few mm gap between them. Bridge the gap with the filament from a small fuse, making sure it makes good contact with both electrodes. Send a large current through the electrodes. The filament will vaporize and an arc will form between the electrodes, turning the tip of the anode at least white hot and causing it to start vaporizing. The power source could be as simple as directly from the outlet ballasted with a 500+ W halogen light or heater (even better if it has a switch), but I recommend using an isolation transformer (1:1) of sufficient rating (if you don't have one, just use two microwave oven transformers back to back, with their high voltage secondaries connected together -- note that this configuration will cause the transformers to heat a lot, so it should not be run more than a couple of seconds). Discharging a capacitor will not work here, as the pulse doesn't last long enough. If you don't want to have to reload the filament every time, you could make one of the electrodes movable and adjust it with pliers with insulated handles; briefly touch it to the other electrode to start the flow, then pull away a few mm to get a good arc. DO NOT STARE AT THE ARC --> UV WILL DAMAGE YOUR EYES! Use UV blocking sunglasses. Also, make sure to do it outside or in a well ventilated area. The temperature does break down some of the O3 and NOx generated, but it still stinks and breathing it will hurt you.

The description is long, but I've used this (although not to burn things, just to melt some metals in a ceramic pot, with a 1.5 kW heater in series as ballast). I have no doubt this will very easily ignite thermite (best to heat the thermite from below; do not stick the electrodes in the mixture as it will conduct).

Disclaimer: If you are a newbie and don't know how to handle high voltages, I wouldn't recommend this method. If you damage or kill yourself, you have no one but yourself to blame.

[Edited on 4-2-2005 by Quince]

uber luminal - 4-2-2005 at 13:09

Quote:

I have no doubt this will very easily ignite thermite (best to heat the thermite from below; do not stick the electrodes in the mixture as it will conduct).

Sorry to doubt you, but have you ever put an arc near powder?
not only would an arc not be practical for redox, (cuz if you have the arc, who cares about some dumb redox), but putting any arc near powder sends the powder in every direction but where the arc is. I run into this problem at least twice a week when trying to arc melt germanium or silicon powders/small bits. So I say, crap! and think oh yea, ill just put the arc near the powder and hope the radiated heat melts it, or at least melts it together a little, but nooo. If the arc isnt close enough to the powder where its blowing it everywhere, its not hot enough to melt it. (granted we arnt trying to melt the redox components, just ignite them, I still stand by the fact that it will blow the powders everywhere, unless maybe you have 600 amps handy, then the heat might be sufficient, but that goes back to the why bother stage.

btw, the way I get around the arc-powder problem at work is to put the powdered stuff under a large piece of metal to be alloyed. If its all powder, we have cranked the amps up into the 600-800 range and used a circular motion around the sample alloy. this ussualy gets it to stick.

and I have gotten KMnO4 and glycerin to work. Iv found it easiest to pour a little glycerin onto an edge of the redox components, and then use a scoopula to put some KMnO4 into the glycerin puddle. That works better than putting glyercerin into a divit of KMnO4 powder (and less wasteful of the oxidizer!)

Saerynide - 4-2-2005 at 19:34

Quote:

Originally posted by uber luminal
and I have gotten KMnO4 and glycerin to work. Iv found it easiest to pour a little glycerin onto an edge of the redox components, and then use a scoopula to put some KMnO4 into the glycerin puddle. That works better than putting glyercerin into a divit of KMnO4 powder (and less wasteful of the oxidizer!)

Ooooohhh... thanks

I tried adding glycerin to KMnO4, but that never worked. This time, if sparklers dont work, I'll try this

Quince - 5-2-2005 at 03:30

Quote:

Sorry to doubt you, but have you ever put an arc near powder?

No, but close: I have put a 5 cm, 1+ kW DC glow discharge (MHCD sustained) to powder (sugar -- quickly turned to ash and gas). Modified microwave oven transformer->rectifiers (chained common ones)->CLCRC filter (total 160 uF / 3 kV capacitance, the L is handwound around salvaged tranny core). I'm replicating Hill's Plasmatronics, except without helium, as MHCD techniques now allow large glow discharges in air without cathode fall instabilities and discharge-to-arc transitions. It's true that the glow discharge moves less air than an arc (AC at that), but I doubt that the arc would blow heavy metallic-based powder around (especially if binded with plaster as suggested by someone).

[Edited on 5-2-2005 by Quince]

Mr. Wizard - 5-2-2005 at 05:19

Use 6" of 1/16" flexible steel cable hooked to a set of car jumper cables. It gets white hot incandescent within seconds and will light even course thermite.

Theoretic - 6-2-2005 at 10:17

You could take some anhydrous CuCl2 and wrap it in Al foil, this can be ignited with a candle and gives a very bright and (presumably) hot white flame which I'm sure will ignite thermite.

Really?

chloric1 - 6-2-2005 at 16:45

Never tried this. Maybe you could put some aluminum shreds in with the cupric chloride? Hmmm, like to see this work.

Saerynide - 6-2-2005 at 22:17

The light bulb did not work

I tried a drop of glycerin then sprinkling on KMnO4, but nope, that didn't work either. I think I added a bit too little KMnO4 (I usually use too much and end up wasting it, so I was trying to be more conservative time time :mad:

).

I wonder, would it work if I put a few drops of glyercin in a divet of thermite, then scoop on a spoon of KMnO4? Or would all the glycerin get soaked into the thermite and nothing would happen?

Btw, do you usually powder your KMnO4? (if you do, maybe thats why mine doesn't ever work

)

I am a fish - 7-2-2005 at 02:06

How long did you leave the Potassium Permanganate / Glycerol mixture before disposing of it? There is usually a significant delay between the two being mixed, and the mixture igniting.

Saerynide - 7-2-2005 at 03:23

A long time. Ive seen it take a long time before, but this one, it just sat there, and did nothing, not even after a few minutes :mad:

The_Davster - 7-2-2005 at 15:40

What temperature was it when you tried this? At times I have been unable to have sucess with permanganate/glycerin when it is too cold outside.

uber luminal - 7-2-2005 at 16:16

Quote:

but I doubt that the arc would blow heavy metallic-based powder around (especially if binded with plaster as suggested by someone).

it really does blow it around. it doesnt matter what the density is. I have blown tungsten bits around. If you can blow tungsten, im pretty sure it wont matter what the material is. I deal with this on a weekly basis, its a pain in the ass.

Saerynide,
I think the glycerin would move too quickly and contaminate your mix if you dropped it right into the redox components. My KMnO4 is a dry purple powder itself. I bought it on ebay for $10 /lb.

You can use KMnO4 as a liquid, and it will react with the sugars (as they dissolve into the aq soln), but it will not get hot enough to do anything with it, you probably wont even see anything happen because the concentration of the KMnO4 is soooo looow.

Saerynide - 8-2-2005 at 02:34

My KMnO4 are little crystals. I guess I should grind it up into powder.

uber luminal - 18-2-2005 at 13:34

I just figured out this week that model rocket starters (the kind that hook up to a lantern batt.) start most thermits (except I never got it to work with WO3. but I might have had the ratio wrong too)

Igniter

MadHatter - 18-2-2005 at 21:10

How about the permanganate with a drop of concentrated sulphuric acid ? Wouldn't the
resulting manganese heptoxide initiate the reaction ?

darkflame89 - 19-2-2005 at 00:41

Saerynide, there's seems that a minimum of amount of redox stuff to use. I used the same stuff as you, probably both glycerin and potassium permangante were both bought from the pharmacy as well. The First time i tried this, i used too little KMnO4, as a result nothing worked, the second time, i used a bit more KMnO4. Still after waiting 5 mins(a very long time), nothing happened to the mixture. Upon this i got impatient and procured a dropper and dropped a drop of water on to the mixture(don't drop too much water), the mixture immediately flared satisfyingly.

I figured the glycerin was too pure, and it did not have intimate mix with the KMnO4. When a bit water was added, both ingredients mixed and the reaction occured.

I tried the reaction another time, this time downstairs, in the garden. I poured a large amount of KMnO4 out and poured abit a glycerin on to it. After 5 seconds the reaction started. I do not this the result due to the presence of wind(Singapore weather is humid).Previously the experiment was conducted at home in a metal tin. But it appears as though that minute amount of water is required to start the reaction if the glycerin is quite pure.

[Edited on 19-2-2005 by darkflame89]

Quince - 21-2-2005 at 21:22

I've never ever been able to ignite thermite. The iron oxide I use is the grey ferrous oxide made by burning steel wool in an airflow, powdered with a pestle and mortar.

Is it possible to ignite thermite without magnesium, or potassium permanganate, or chlorates, or sulfur, none of which I have access to? My current arc setup reaches about 2000*C, which I'd think would be enough, but it doesn't seem to do it...

thedestroyer5150 - 22-2-2005 at 02:48

Magnesium ribbons burn at around 1500 F and ignite the thermite which I've seen get up to 4000 F. If the reason you don't want to use it is because it's hard to find; you can get some at unitednuclear.com; there's lots of great shit there.

Quince - 22-2-2005 at 16:41

They won't ship to Canada.

chemoleo - 22-2-2005 at 16:50

As I said many times before, a couple of sparkling candles will ALWAYS do the job. I yet have to find a thermite where they didn't.

Quince - 22-2-2005 at 20:42

I called the fireworks store here and they said fireworks (including sparklers) can't be sold this time of year (I'm in BC).

The_Davster - 22-2-2005 at 21:05

You should be able to get sparklers in party and/or dollar stores. That is where I get mine.

[Edited on 23-2-2005 by rogue chemist]

HNO3 - 23-2-2005 at 21:03

My first thermite was contaminated heavily with styrene (I didn't know it). Sparklers didn't touch it. Call me an idiot, but my latest thermites have been ignited with a propane torch.

Quince - 24-2-2005 at 01:21

How could your thermite have been contaminated? From the aluminum?

uber luminal - 24-2-2005 at 23:57

Quince. Go to Hobby shop. Look at rockets section in hobby shop. Locate rocket engine starter kit. Buy kit. run run. hurry home. Try thermit.

your ratio also might be wrong. if not, try adding a little bit more Al to the mix.

the rocket starters are meant to be used in starting powdered reactions.

another thing to try when the KMnO4 doesnt work... is to use a lot of it. You of course have to add more sugar too. I ran a series of KMnO4 tests with my digital thermocouple. a pinch + a drop will trigger around 480C. a few pinches and a large drop get up to 520. more gets up to 590. even more than that and it gets harder to react it all, but I suppose if you found a way to do it, you might get even hotter.

As for the spark start in other methods, I know spark plugs also work rather well (its what they used to use at work). just be sure to get the anode close to the mix as thats where the majority of the heat produced by the spark will be.

Quince - 25-2-2005 at 02:43

I got some sparklers. But it didn't start the thermite, as I'm guessing my aluminum is too coarse. But grinding and filing are the only ways I could get some. None of the paint stores or art supply stores around here have aluminum powder. I tried the blender and aluminum foil in alcohol idea from roguesci, but again, too coarse with my blender. :mad:

I doubt anything is wrong with the ferrous oxide, as I made it by burning steel wool, so it should be fine.

[Edited on 25-2-2005 by Quince]

uber luminal - 25-2-2005 at 12:15

quice, dont rely on what should be fine with what you think is ferrous oxide.

I ran a thermit the other night and it only partialy worked. I couldnt figure out why, until there was realization that I used FeO(Ferrous,(II) instead of Fe3O4(triiron tetraoxide,(II,III) like I had calculated for. (both are black powders. people labeling things "Iron oxide" allowed me to make an error.) Given the place I got it from, I thought it SHOULD have been the latter chemical.

chemoleo - 25-2-2005 at 12:48

A well-known trick to get reluctant thermites going (such as SiO2/Al, both powders) is to add sulphur. You get Al2S3 of course, too, but your reaction then generates enough heat.

Anyway, many years ago I used Al shavings (about 1 mm thick , 0.5-2 cm long) with pigment Fe2O3, and this worked ok when several sparklers were tied together. Obviously, the coarser, the more heat is required.

Quince - 25-2-2005 at 14:40

Which iron oxide do I have then by burning steel wool? It's dark grey in color.

Is there some minimum amount necessary to ignite? I've been using at most a quarter teaspoon due to limited amount of ingredients.

HNO3 - 25-2-2005 at 15:26

Quince- I was using copy machine toner. It says right on the label that it contained Iron Oxide...

How could have I known?

Not sure if it applies to all you rotten europeans

, but I got some aluminum powder at a Hobby Lobby(tm). It was called powdered silver guilding or something like that.

Quince - 25-2-2005 at 19:41

Toner particles are coated with a polymer to make it stick to the paper when it goes through the heated roller.

Saerynide - 25-2-2005 at 21:38

Chemoleo: Should the sulfur be added to the thermite or to some extra aluminum and placed on a divet of thermite?

Quince - 25-2-2005 at 22:16

From some searching it seems that both Fe2O3 (red) and Fe3O4 (black) can be used. I have the latter from burning steel wool, not just because of color, but also because it's magnetic.

Adding HCL made some brown solution, so not all the Fe had burned, but most had, so I doubt any of the elemental iron could have really interfered. So my problem must be with the aluminum.

I used a hand blender to pulverize aluminum foil in alcohol (30% water), and evaporated the liquid after filtration to remove larger particles. I used the grey aluminum dust left for the thermite. It still didn't work, even with half a centimeter of sparkler inside the thermite. ARRRGH!!!!! I don't know if the water in the alcohol caused the fine aluminum to oxidize or WTF is going on, but after so much effort I've still failed to get a thermite reaction going. :mad:

Anyone in Canada willing to sell me some aluminum powder (I can pay with PayPal)? I've checked like ten stores and none carry it. Fuck, I can't even buy permanganate anywhere, as the pharmacies haven't used it in years.

[Edited on 26-2-2005 by Quince]

Bert - 26-2-2005 at 04:00

Quote:

Originally posted by Quince
I can't even buy permanganate anywhere, as the pharmacies haven't used it in years.

Don't look in pharmacies. Look at anyplace that sells water softeners/water treatment chemicals. Sears stores in the US still sell it for this purpose, and it is fairly cheap.

neutrino - 1-3-2005 at 05:22

Quote:

Originally posted by Quince
I don't know if the water in the alcohol caused the fine aluminum to oxidize

That would be my guess.

Saerynide - 4-3-2005 at 09:50

I wonder, does it matter which end of the sparkler you stick into the thermite? Do you cut off the metal ends, and shove in that end (lighting the fat end like you normally do)? Or do you stick in the fat end that you're normally supposed to light and instead light it from the thin end?

Quince - 4-3-2005 at 09:56

No man, I only made small amounts of thermite (half teaspoon), and it's impossible to stick the whole sparkler in. I split the sparkler lengthwise and use a 1 cm long chunk of that.

Bert - 4-3-2005 at 10:23

Half a teaspoon of thermite. Enough said. The reason you can't light it is because you can't find it. Also, unless you've got a very good scale (accurate to a couple of milligrams), you are unlikely to have the ratios correct. Quince... I'd suggest you stop trying to burn anything inside your parents home. I'd also suggest you back off from energetic materials for a bit and thoroughly study basic chemistry. Boreing, I know. But just jumping in without a strong understanding of what can be done and how will either waste your time and resources or get you hurt. If you haven't allready found the E&W forum, go there and do a LOT of reading before either trying any potentialy dangerous experiments or posting questions that have been endlessly asked and answered in the past.

[Edited on 4-3-2005 by Bert]

Quince - 4-3-2005 at 10:47

My parents are on the other side of the continent. I'm a graduate student renting a place. I measured the reagents using a scale accurate to 0.1 g. "Can't light it...can't find it" has nothing to do with basic chemistry, so I don't see where that bit of patronizing is coming from. And by the way, the word is spelled "boring" with no 'e'.

[Edited on 4-3-2005 by Quince]

Bert - 4-3-2005 at 10:57

You can't light thermite. You can't find basic OTC chemicals. I'm not trying to be patronizing, everyone had to start somewhere. But for some reason, 30 odd years ago when I was 14 I made and ignited thermite on my first try. And a bit of basic searching on sulfates with metallic fuels would have answered the other thread you started. If you're a grad student- It isn't in chemistry. English lit perhaps?

(edit)
Just looked at the rest of your 108 posts here since you joined 1/31/05. Apparently you have allready found roguesci. Also quite evidently, you ask LOTS of questions without searching thoroughly.

[Edited on 4-3-2005 by Bert]

Saerynide - 4-3-2005 at 17:51

There is no need to chastise Quince for what he said. Just because someone couldn't light thermite on the first try, it doesn't somehow make them inferior to someone else who could.

And so what, if he's not a chem student? It's not like everyone here is, and you dont have to be to be if you only enjoy it as a hobby.

Quince - 4-3-2005 at 22:37

Quote:

Originally posted by Bert
English lit perhaps?

Ha, you must think you are so witty! Computer science, actually. But as I value quality literature and other art, I say you are quite arrogant to insult non-scientific academic disciplines.

uber luminal - 5-3-2005 at 07:22

I think its great that Quince has found an interest in chemistry. (even if its starting with smoke and fire types of reactions). I also think its great that he hasnt given up trying to do things. Not all learning has to be done from the ground up, especialy if you allready have a standing elsewhere else.

Quince, I would try making a little bit more than the 10? 20? gram mixtures that you have been trying.

I usually make a test batch by starting with 27g of Al and add the metal by ratio from there. Mix the load, then divide it back up into 2 or 3 seperate loads.

-edit- Also, back with the Al foil/blender. I can't think of why the Al would have turned grey. was it like a light grey? or a dull dirt looking grey? I really doubt the Al foil was oxidized in the proccess of blending it. the next question I have is, how small are the pieces? The best results Iv had (aside from buying good stuff on ebay), have been from Al filings. If all else fails you could take a trusty large grain file to the bottom of a few Al cans (or whatever source you have)

[Edited on 5-3-2005 by uber luminal]

Quince - 5-3-2005 at 09:20

I have many other hobbies (electronics, physics, philosophy, piano, organ, books, hiking, cognac, women), which means sometimes I have to take shortcuts and decrease the DIY part in order to have time for all of them. I prefer generalizm over specialism. For me knowing nothing about everything beats knowing everything about nothing.

I've had just one chemistry class in my life (back in highschool), so I can't be expected to know anything when I'm getting started. Searching helps to some extent, but given that chemicals can be written in multiple ways makes it easy to miss results, just as difficulties in knowing the most likely way something was worded makes finding relevant results also a problem.

[Edited on 5-3-2005 by Quince]

chemoleo - 5-3-2005 at 09:45

Quince, despite the sympathy vote, you aren't off the hook.
Indeed you ask many questions that have been debated to death elsewhere (like that vacuum destillation one). 110 posts, where more than 2/3 is on stuff that's been debated elsewhere is NOT good.
When people tell you half a teaspoon is WAY too small an amount then accept it. There are people who have tried this many many times.
The trouble is with thermites, the reaction needs to 'catch fire', i.e. the heat it produces must be enough to propagate. With small amounts such as yours it has barely a chance to propagate. Neither do you know the quality of your oxide (and that of the Al for that matter). 1cm of a sparkler piece is WAY too little as well. The sparkler (or several tied together) should stick INTO the mix (either end works). Further, it always helps pressing the thermite, to get it into more immediate contact with the igniter. But half a teaspoon, with homemade material... I'd be surprised actually if you got it to work.

I really suggest you take some time off posting, and start reading the threads here (and EW). Noone else seems to ask such questions, so who ought to do the reading?

I am very tempted to close this thread, it's veering off way into the practical trivial, and all the important bits have been said. Take that as a warning...

So back on topic now chaps!

I am a fish - 5-3-2005 at 10:40

Quote:

Originally posted by Quince Searching helps to some extent, but given that chemicals can be written in multiple ways makes it easy to miss results, just as difficulties in knowing the most likely way something was worded makes finding relevant results also a problem.

Then perform multiple searches. When searching through previous topics, I usually make several searches, to avoid missing anything out.

Bert - 5-3-2005 at 11:34

I will try to make this an informative and useful post, rather than a criticism.

1. Tiny samples of thermite (1 gram? 2 gram?) are difficult to weigh properly. 10 milligrams is a large error in a one gram sample. Make AT LEAST an ounce, then you will also be able to do something fun like welding or puncturing a piece of steel with your thermite.

2. As a mass decreases in size, the ratio of surface area to volume increases to the extent that a reaction may lose heat by radiation from the surface too fast to self sustain. Once again, a larger sample is the answer.

3. I lit my first sample by means of a step prime. A cone shaped well was made in the top center of a pile of thermite, and filled with succeeding layers of composition made with varying proportions of a crude black powder mix with thermite- i.e., bottom layer was 75%: 25% thermite : black powder, middle layer was 50 : 50, top layer was 25 : 75.
This allowed use of a firecracker fuse to ignite the sample. This is a common technique in pyrotechnics, which may be applied to rolled stars as well. The use in the crude BP igniter of a somewhat higher proportion of Sulfur to charcoal than normal for propellant uses may also be of benefit.

Additionally: the photo of a clearly highly exothermic reaction being carried out on a textile surface shows some lack of forethought. When igniting a sample of thermite you should be aware that the reaction may progress with explosive swiftness, heating air trapped in the powder so swiftly it expands quickly enough to blow molten iron all over the area. Similarly, small amounts of water trapped in any nearby material, such as wood, sand or porous ceramic will guarantee a steam explosion. This also will occur if thermite is ignited on a cement or plaster surface as the water chemically bound in the cement or plaster WILL be released as steam.

Granted a safe place to perform such an experiment, I would proceed thus: Take clean sand, previously baked dry in an oven and make a ring on the (dry, clean) steel target to be welded or punctured sufficient in size to retain the liquid Iron in the area desired. This may be accomplished by taking a drinking cup of the appropriate size and setting it on the target, piling sand around it and carefully picking it up. Fill the cavity in the sand with the mix. DEEPER is better than WIDER Ideally, a cone shaped charge will concentrate the molten iron on a small bare area of the target at the bottom of the cone for the maximum spot heating effect. A "V" shaped trench in sand over the juncture of two steel plates may be used for welding them- In all cases, make sure that whatever is under the plate will either retain the weld material safely, or allow the molten iron to run away safely if a puncture is the intended effect. Do it on bare concrete and you may be eating molten iron and glass.

[Edited on 5-3-2005 by Bert]