He came down from Queensland to visit us, and some other people, the other week.
And recorded some video, including some flying off Echo Point near where I live. Though with entirely too little buzzing of trees and tourists, or seeing how low he could go before the edge of the cliff tested the effectiveness of the copter's lost-signal configuration.
I am not in the Echo Point footage, because I was not there, because I am an idiot.
This extraordinary object looks as if it came from outer space.
It's around 11 centimetres long (4.3 inches). It weighs a bit more than 170 grams (six ounces). Its overall colour is a sort of greenish black. But it's entirely composed of darkly reflective crystalline facets, ranging in size from microscopic to about 8mm (5/16ths of an inch) in length.
On close inspection, the mass of crystals comes in a dark rainbow of different colours; yellows, blues, purples and reds.
Just like solid chromium, this stuff doesn't look real. Like the chromium, it looks more like some sort of movie prop. But my chromium lumps look like rocks spray-painted silver for an Original Series Star Trek episode in which those silver rocks were the most valuable object to appear. This stuff isn't nearly as shiny, but is much flashier, if you get my meaning. It's detailed. It's high-definition. It looks like a prop from a sci-fi movie we won't have the technology to make for another ten years.
You know what it looks like? It looks like black kryptonite, that's what it looks like.
(If you ask me, it looks better than the actual black kryptonite prop from Smallville. I presume you all share my incredulity that it took them until 2004, the 66th year of Superman's existence, to add the seemingly obvious black to the host of other kryptonite colours. Oh, and this Flickr user had the same thought, about what looks to me like the same material.)
Or possibly this stuff is what was left over after Gus Gorman boiled some home-made kryptonite in ammonia and ether and then smoked it.
This mass of black crystals is actually a chunk of crystalline silicon carbide (SiC), which I purchased quite cheaply on eBay (see below. There's video, too!).
This means it must be man-made, because natural, "native", silicon carbide does exist, but it's fantastically rare. It takes a lot of energy to persuade silicon and carbon to form a molecule.
Native silicon carbide is known as "moissanite", and so are simulated diamonds made from high-purity SiC. Far, far more SiC is made for use as an industrial abrasive or super-hard coating for tools, though, and some such process probably made this lump of the stuff.
Silicon carbide is so widely used as an abrasive because its Mohs hardness is as high as 9.5, between corundum (sapphire, ruby, and a component of emery) at 9, and diamond at 10.
Those numbers are misleading, because the Mohs scale is ordinal; it tells you what's harder than what, but not by how much. There are different ways of measuring the hardness of a material - compare and contrast the Knoop, Vickers and Rockwell tests, for instance. Whatever method you use, if you do a relative-hardness test, pretty much everything looks sick compared with diamond.
Assign a relative-hardness score of 10 to diamond and, depending on what test you use, corundum may score as high as 2.63 or as low as 2.2, and silicon carbide may score as high as 4.63 or as low as 2.5. For further comparison, quartz, generally regarded as a pretty hard material, scores down around one, if diamond is 10.
(In view of this, the fact that humans are now finally more-or-less managing to make exotic materials that are actually harder than diamond is quite amazing. The most widely used new super-hard material is diamond-like carbon, which as the name suggests isn't actually "better" than diamond, and two of the other candidates are actually just novel forms of diamond. Only minuscule amounts of the best non-diamond candidate have been made to date - with some debate over whether any of it has actually been made at all. But one way or another, we're doing it, and the achievement is a lot more impressive than a mere Mohs hardness of "11" would suggest.)
I don't know exactly how my lump of SiC was made, but I suspect it was an unwanted byproduct of some industrial process, perhaps one or another kind of vapour deposition. The carbide is meant to coat drills or saws or something, but it deposits elsewhere on the equipment too. When some lucky duck gets to clean out the machinery, stuff like this crystal mass ends up in their bucket.
Most industrial waste is not particularly decorative, but every now and then, somethingextraordinary comes along.
I also don't know how pure this carbide is. High-purity silicon carbide can be black, just like this material, but there may be various impurities in there too.
The surface is definitely not pure SiC; the rainbow reflections are created by a very thin layer of silicon dioxide on the surface. This interacts with light in the same way as various other super-thin coatings, like the surface of anodised titanium, the "rainbow of temper" on steel, or a soap bubble, for that matter.
Silicon carbide is very hard, but rather brittle. If you buy a chunk mail order like I did, you're going to get a few broken-off crumbs in the box along with the main piece, unless the seller packed the carbide in thick cotton wool. And if they did pack it in cotton wool, you're going to spend forever picking cotton shreds off the pointy crystals. Just hitting the thing with a blowtorch might be a faster solution. Or it might heat-shatter.
You don't really have to treat SiC like the egg of a tiny bird, though. When I deliberately broke off a little crystal stuck to the main mass by a couple of millimetres of hair-thin filament, I was surprised to see the filament bend a good five degrees before it snapped. And tiny crumbs coming off even a small SiC lump won't make any obvious difference to its appearance.
One thing you probably don't need to worry about your silicon carbide doing is melting. The melting point of pure silicon carbide is 2730°C, 3003K, or 4946°F in the old money. So you may be able to melt it with an oxy-acetylene torch; the theoretical perfect-combustion temperature for that is around 3500°C. Oxy-hydrogen might manage it, too. MAPP-gas and oxygen probably won't cut it, though, and no cheap butane torch will come within a hundred miles.
Silicon carbide was the material used for the very first light-emitting diode, way back in 1907, though this discovery was largely ignored at the time. That could be why nobody managed to make an LED bright enough to be useful for anything until the Sixties. Henry Round's original discovery was still scientifically important, though, and I swear I managed to get a tiny spot of my chunk of SiC to light up under a pin connected to minus 12 volts. But once I set my camera up, it refused to do it again, no matter what I poked with the pin or where I attached the positive cable's alligator clip.
I think having an alligator clip as the positive terminal, rather than for instance sitting your SiC chunk on aluminium foil that's connected to positive, is important - you need pressure on the SiC to get a decent contact, and the positive connector needs to be close to the point you're poking with the negative pin, or the semiconducting SiC won't let any current flow. With the clip close to the pin (less than a centimetre), something above 20 volts always persuades my SiC to allow current to flow, but that doesn't give the LED effect, just little blue sparks. You're looking for something greenish-yellow, as in this Wikipedia picture:
(The picture is from this page, which contains further instructions on how to try this experiment yourself. And then there's this dude, whose carbide lump seems happy to light up all over, damn his eyes.)
Trying, and failing, to make my own carbide-LED picture was quite frustrating. I can see why people in the early days of radio were so happy when they could buy machine-made vacuum-tubediodes so they didn't have to fool around with super-fine wires and lumps of galena any more, poking around all over the crystal like a tiny pirate seeking one buried treasure chest on the whole island of Barbados.
Aaaaanyway, you may be pleased to know that I am now finally going to tell you where I got this stuff, and what it costs.
Getting some
I bought a little chunk of crystalline silicon carbide on eBay a few years ago, from this seller, but they don't have any SiC for sale at the moment. This new bigger chunk was another eBay purchase, for $US28.17 including delivery to me here in Australia, from this seller (who's here on eBay Australia, here on eBay Canada, and here on eBay UK).
As I write this, they've got one more lump of the stuff, closer to spherical than mine and weighing 210 grams.
The inimitable Theodore Gray has a chunk of this stuff too; he bought it on eBay as well, but from a seller who called it "native bismuth". Dark SiC crystals resemble bismuth hopper crystals (see here) in colour, but that's as far as the resemblance goes.
(Theo also has this different-looking SiC sample, which was also sold as bismuth. And then there are these high-purity crystals, transparent green with no oxide layer. Oh, and on the subject, if you get a solid block of carbide but yourplutonium hasn't arrived yet, you can pass the time with some microwave metal melting!)
Nobody on eBay seems to be selling silicon-carbide "bismuth" at the moment; there's plenty of "native bismuth" crystals that're obviously actually purified bismuth crystallised by the standard stovetopmethod, but at least those actually are bismuth, so by eBay fake-minerals standards no great crime is being committed.
And now: Twinkling!
Behold, the silicon carbide lump, and the chromium, and a couple of large oval-cut cubic zirconias ("CZs") into the bargain. They all look impressive in sunlight.
(These videos don't have sound. Feel free to add your own vocal "ting" sound effects to synchronise with the reflections and refractions.)
The smaller CZ is, at about 36 by 29 by 22 millimetres (1.4 by 1.1 by 0.9 inches), comfortably in the Crown Jewels size range. If it were a diamond, it'd be around 155 carats (as a CZ, it's 255 carats - CZ is about 1.6 to 1.7 times as dense as diamond). This is a bit less than the original cut of the Koh-i-Noor, but about 1.5 times the Koh-i-Noor's current size.
The larger CZ is about 52 by 38 by 28 millimetres (2 by 1.5 by 1.1 inches), and weighs 132.5 grams; a diamond the same size would be about 400 carats, far larger than any of the world's famous colourlessdiamonds, and a little less than the total weight of all of the multicoloured diamonds in the two "Aurora" displays.
I bought both CZs in 2009 from this eBay seller; the smaller one cost me $US19.95 delivered, and the bigger one was $US37.95.
That seller doesn't seem to have a lot of huge CZs on offer today, but if you use the always-entertaining "highest price first" sorting option but set a price ceiling at, say, $100, then in among the eBay listings for bags containing many small CZs, there are plenty of monster white and coloured stones.
(Here's that search on eBay Australia; it's here on eBay UK, and here on eBay Canada. I strongly recommend you buy at least a pocketful of small CZs; they make novel presents, and you can also wrap them in black felt, go to a cafe with a friend, wait for people to look, and then make everyone think some serious state secrets are being sold.)
And this is a nice bit of microscaleminimalism, but still not what you'd call faithful to the source material.
But, gentle reader, there is a solution. Though it carries a price - a price you may adjudge too high.
If you want a minifig-scale Dalek that actually looks like a Dalek, you can have it. All you must do is... I fear even to say it... is buy off-brand Lego.
I feel so dirty.
But just look at these little buggers.
Daleks! Made out of Lego-compatible blocks! Properly built up out of pieces, too, not just single-piece lumps!
Each Dalek breaks down into six major pieces and three minor ones. The baseplate, the skirt, the sucker-and-gun section, the shoulders, the neck and the head are all separate and about as Lego-compatible as it's possible for them to be, given their shape. The minor parts are the sucker, gun and eyestalk, all of which fit in holes too small for any other Lego piece or sub-component I can think of right now. The three minor pieces all have to point straight out, not swivel, but the head turns. (So do the shoulder and neck pieces, but not the sucker-and-gun section, which was never able to turn on-screen either, until 2005.)
These not-actually-Lego Daleks are made by Character Options, who make various other licensed action figures and playsets and such. (All eleven Doctors? Fifty quid as action figures, twenty quid as pseudo-Lego.) Their "Character Building" brand has a variety of Lego-compatible Doctor Who sets, mostly just minifig-scale Doctors and companions and monsters. I bought the "Dalek Army Builder Pack", which gives you five red Daleks and nothing else. There are yellow and white Daleks in other sets, and Character Building also has one of those gashapon deals going where you can spend two pounds on a minifig from, thus far, twoseries, but not know what one you're going to get. You can get a blue Dalek that way if fortune favours you; any other colours, you're thus far going to have to paint yourself.
(You're also going to have to break out the paint if you want the Dalek bumps on the skirts to be a different colour from the skirts. In this scale the bumps are only about four millimetres in diameter, so it's not surprising that Character Options, um, opted, to leave them the same colour as the skirt.)
The Character Options sites lists the Army Builder Pack for £9.99, which is around $16 Australian or US, as I write this. I got mine on eBay for only £10.70 including delivery to Australia from this UK seller (here on eBay US, here on eBay Australia), but they don't have any more for sale as I write this.
There are plenty of other eBay sellers who do have stock, though; this search ought to find them all. The cheapest ones are all selling one individual Dalek parted out from a kit; the cheapest Army Builder set as I write this is £7.99 plus postage. There are plenty of sellers on Amazon, too.
The Character Building Daleks do have one flaw, though, which may be even more of a problem than the fake-Lego problem:
The Teletubby, a.k.a. Power Ranger, Daleks are the ones last seen on TV in 2010's Victory of the Daleks, when the Doctor was, for once, conclusively outmaneuvered by his enemy, and tricked into reincarnating these purestrain "New Dalek Paradigm" monsters.
(And, incidentally, there were also Spitfires in space.)
I thought Victory was a good episode (and quite funny, which counts for a lot), except for some industrial-grade schmaltz involving an android. But the new colour-coded Daleks at the end, each with their own more or less peculiar name, were not well received by the fans. Especially the... really enthusiastic fans.
The New Paradigm Daleks are big and shiny and brightly coloured, and have a great hunchbacked extension on the rear of their bodies, which gave me the impression that the props had for some reason been designed to have two human operators inside. I'm sure that isn't actually the case - these were Daleks in 2010, not Jabba the Hutt in 1983 - but there the huge lump is, or at least was.
Perhaps the Teletubbies are never coming back. Perhaps they're coming back but along with the older kinds. Who knows. (Free plot idea: The new ones are fat because they are pregnant with a much better design of Dalek.)
Anyway, these little Lego-ish ones do look a bit like them. But they're clearly not the same. The hump is less pronounced, the head isn't positioned way forward on the shoulders, the weapon-and-sucker section doesn't bulge out from almost vertical sides, and they've got that odd zipper-like grille thing on the back, but who cares.
I don't think they quite match any Dalek that's ever been seen on screen, but the Dalek props have, over the years, also failed to match each other in various ways, even if you've managed to erase the Peter CushingDalekmaniamovies and their Daleks armed with fire extinguishers from your mind.
(The New Paradigm Daleks stand significantly taller than the old ones, too; the Character Building ones are about a head taller than a standard minifig with no hat on, but are I think about the same height as the Character Building pseudo-minifigs.)
So if your interest in the racial purity of Daleks is only exceeded by their own, then you may consider these ones unacceptable. But they're really not very Teletubby-ish.
And, c'mon. Lego-compatible Dalek parts!
Haven't you always wanted the Doctor and a companion to be desperately hiding as the sound, tic-tic-tic-tic-tic-tic-tic, of robotic spider-legs approaches, and stops, and then a spray of baleful blue eye-lights spotlight them and the Mark V Travel Machine rears up, twenty feet high, dozens of its blackly shining sense globes irising open to extrude claws and tentacles and saws and injectors and suction feeders and flensers and écraseurs and deglovers, even as its battery of far-too-merciful gunsticks retract, and in a voice that breaks windows it SHRIEKS-
...well, actually these things probably won't greatly help you make that.
But if you let your kid at 'em, imagination ought to fill the gaps.
If you're not in Australia, and not interested in polycaprolactone, this post is not for you.
Regarding that second criterion, though, I think pretty much everyone should be interested in polycaprolactone. I'd actually go so far as to say that every home should have some, even if you're not at all "handy". Just put it in that kitchen drawer with the screwdriver, the hammer, the dried-up epoxy and the random screws and washers.
Well, put it there when you've finished playing with it, anyway.
...this, um, thing, polycaprolactone (which is sold under several easier-to-remember brand names) is a remarkable substance.
It can be moulded like rather sticky, see-through clay when hot (its melting point is about 60°C, but it's comfortable to handle at quite high temperatures, thanks to low thermal conductivity). When it cools, it turns into a smooth opaque white plastic about as strong, and tough, and easy to shape with other tools, as nylon. You can use it to do anything you could do with nylon, except of course withstand temperatures above 60°C.
And, unlike Sugru and various other putties and clays, polycaprolactone is reusable - just heat it up again. It'll also last forever on the shelf, and isn't even toxic, unless you set it on fire and inhale deeply.
You need hot water to soften polycaprolactone, but that's the only thing remotely dangerous or difficult about this stuff. Any child old enough to boil water without supervision can use polycaprolactone to make, fix or modify things. Because you can reuse it as much as you like, polycaprolactone is also an excellent do-it-yourself material for klutzy adults.
I spent a while in the 2010 post talking about where to find polycaprolactone, and what it cost. At the time, it wasn't hard to find the stuff here in Australia, but it was a bit expensive.
Now one Peter Edmunds, the proprietor of plastimake.com, is selling polycaprolactone locally for good prices.
Plastimake-branded polycaprolactone comes as the same white granules as pretty much every other brand. ("Friendly Plastic"-branded polycaprolactone is rather more expensive, but can be had in numerous colours and finishes.) As I write this, there are only two package sizes available from Plastimake; a hundred grams is $AU10 including delivery anywhere in the country, and 800-gram jars are $AU30, plus a flat fee of $AU10 delivery for as many jars as you like. They accept PayPal or credit cards for payment.
(Plastimake sell on eBay as well. Prices are the same.)
For comparison, Jaycar are still selling Polymorph-branded polycaprolactone in Australia. Their pricing starts at $AU11.50 for 100 grams - plus delivery, if you're buying mail-order - and drops to $AU8.95 per hundred grams if you're buying a kilo or more.
So if you're building your own Plastic Pal Who's Fun to Be With and want four kilos of the stuff - which is quite a lot, because polycaprolactone is only slightly denser than water - Jaycar will relieve you of $AU368 including road-freight delivery, versus only $160 delivered from Plastimake.
The UK eBay dealer (on ebay.com, on ebay.co.uk) that I recommended in the last post is still selling Polymorph-branded polycaprolactone, too. A kilo from them is £15.10 (about $AU23, as I write this) plus international delivery, which currently isn't specified for this largest size. If four one-kilo bags cost the same to send to Australia as four kilos worth of their 750-gram bags, though, the delivered price for four kilos would be about a hundred quid, or $AU153.
So Plastimake are ahead by a bit for small amounts - and if you've never played with polycaprolactone before, a hundred-gram bag will be plenty to give you the idea - and they charge about the same for large amounts delivered to Australian customers as the best eBay dealer I've found.
(If you want to place a really big order, you can also contact Plastimake for a further discount.)
Plastimake are brand new, so I suppose it's possible that Peter Edmunds will turn out to take your money and run, or something. Presuming he is not a rip-off artist or crazy person, though, there's really no excuse any more for Australians to remain polycaprolactone-less.
The stuff really is very fun, very useful and very easy to work with, and it tremendously appeals to the large penny-pinching lobe of my brain. It'll never go stale or dry out, and if you drill or carve something you've made out of it, you can collect and reuse even tiny shavings.
UPDATE: As requested in the comments below, here are a couple of little (silent) video clips of the chromium lumps in the sun, plus a chunk of crystalline silicon carbide and a couple of enormous cubic zirconias:
As undisputed king of the element-collecting hobby Theo Graypoints out, chromium is commonplace in the modern world, but only in ultra-thin electroplated layers on other substances. There's no need to use more than a super-thin layer of chrome to make some car-part shiny, because chromium in air protects itself from corrosion with a hyper-thin oxide layer, sort of like aluminium, but more so. The chrome oxide layer, unlike the aluminium layer, is so thin that you can't even see it, so chrome looks freshly-polished all the time.
This stuff is actually so shiny that it looks fake, like rocks spray-painted silver and given an outlandish name in an episode of Star Trek. It feels more real when you pick it up, though, because chromium is only a little less dense than iron. It's also nonmagnetic, and non-toxic.
Various chromium salts are bad news and can be made accidentally in the home, by for instance using a stainless-steel object as the sacrificial anode for electrolytic de-rusting. But the metal itself is benign.
I got my chromium, and a few other trinkets over the years, from eBay seller "The Mists of Avalon" (on eBay Australia, on eBay UK). From their name, you'd expect them sell a lot of metaphysical wank - and yes, they do! But right next to their "Wiccan/new age/spiritual/pagan" and "Healing/metaphysical crystals" categories, though, they've got umpteen science collectibles, and the listings for those items don't even contain the traditional fanciful explanations of the supposed effects of the periodic-table sample you're considering buying on chakras and meridians.
At the moment, Mists of Avalon seem to be the only eBay dealer selling these nice rock-shaped chromium lumps. They've got one listing for chunks not unlike mine, and another listing for "more than 10" bags of smaller lumps. (They've also got a listing for some chromium powder, but you probably don't care about that.)
There are a few other eBay dealers selling chromium, and other element, samples of one kind or another (on eBay Australia, on eBay UK). There's SoCal Nevada, for instance; I've bought a few sciency knick-knacks from them, too. They currently have one tiny crystal of chromium, and a couple of big machined disks of the stuff.
Theo Gray's pals RGB Research will be pleased to sell you a hefty cylinder of high-purity chromium, of the same standardised 35 by 55mm size as the tungsten and magnesium ones I've got (they don't have any of the big tungsten cylinders for sale at the moment, though) for the trifling sum of $US325 plus delivery.
I'd hold out for the rock-shaped lumps, though; they really show off the bizarre nature of this substance. Tungsten doesn't look like much; its special characteristic is its extraordinary density, making it a plausible stand-in for plutonium.
The last time I used an infrared thermometer it was in a lab at university, and the thing was the size of a shoebox and cost thousands of dollars. I don't know why it took me so long to discover that now they cost fifty dollars, but I did, so obviously I bought one because at that price why not.
I've been having a lot of fun seeing what temperature my walls and ceilings and floors and computers and pets are at, but some things confuse me. The sky, for instance, reads around 5°C when it's overcast (ambient ground-level temp about 15°C), but when it's clear the sky reads about -50°C, day or night. Thanks to the University of Wikipedia I know that the thermosphere is very sparse but can be very hot, and the mesosphere below it is around -90°C; is the minus 50 just averaging those out?
Also, when I shoot the side of a saucepan with boiling water in it, I get a reading of only maybe 50 or 60°C, even if I'm shooting a part that's above the water line and clearly above 100°C because if I slosh the water around it hisses when it touches the inside of that part. What's up with that?
Pablo
The non-contact infrared thermometer is, indeed, a fantastic tool, and toy. Cheap ones usually aren't pinpoint accurate and may be quite severely inaccurate outside their specified temperature range; a -35-to-230°C cheapie, for instance, may still give numbers well outside that range, but shouldn't be trusted.
But as you say, point-and-shoot temperature measurement for under $100 is pretty darn fantastic, even with caveats.
Actually, the absolute lowball price for IR thermometers on eBay these days is less than ten US dollars, including delivery. (The same search on eBay Australia, for any Aussies for whom the "geotargeting" for the other search doesn't work.) You've got to wonder how accurate a $7.50 thermometer can possibly be, and the cheapest ones also run from little button batteries that may not last very long, but I still think a sub-$10 IR thermometer you can put on your keyring qualifies as Living In The Future.
(Most non-contact thermometers have a laser sight, too, allowing you to entertain your cat while you measure its temperature.)
What these thermometers actually measure is lower-frequency thermal radiation. Thermal radiation is light, and can be of high enough frequency to be visible to the human eye - red-hot metal, tungsten light-bulb filaments, et cetera. What people usually mean when they refer to thermal radiation, though, is invisible long-wavelength infrared light. Cheap non-contact thermometers all measure medium-to-long-wave IR, with wavelengths in the neighbourhood of ten micrometers (µm, often written as "um" to avoid the hard-to-type Greek letter Mu).
I think the most common wavelength specification is "8-14um", which includes, according to a common definition, the very bottom of the mid-wavelength band and almost all of the long-wavelength band.
(Medium-infrared is a few octaves below the 700-to-800-nanometre near-infrared that human eyes can actually detect, if it's bright enough. I've made both versions of those IR goggles, by the way; they work great!)
There are three factors that can throw off this sort of temperature reading.
The first is the emissivity of whatever you're pointing the thermometer at. There's no such thing as a pure black-body radiator outside Physics Experiment Land; for this reason, no real substance emits as much IR at a given temperature as it should, though many substances are pretty close. Consumer IR thermometers just make a guess about emissivity; I think most of them are calibrated for an emissivity of 0.95.
Fancier IR thermometers, like this $AU189 one for instance, not only have a wider temperature range and higher accuracy, but also let you correct for emissivity and even the distance to the target, which is the second factor that's affecting your temperature readings. The distance-to-target matters because air emits IR like everything else does; it doesn't emit much of it, because of its low density, but the more air there is between your thermometer and its target, the more the temperature of that air will skew the reading.
(The cheapest eBay thermometer I've found that claims to offer emissivity adjustment is the one found by this search, for £29.99 delivered, which is about $US48 or $AU46, as I write this.)
Emissivity is a much bigger factor than distance to target for most readings, though. Look, for instance, at the emissivity list here, or the bigger one in this PDF. Some things - unfinished wood, clay, human skin - have emissivity well above 0.9. Other things - polished metals, in particular - have extremely low emissivity, of 0.1 or less. Even rough-finished and/or oxidised metal commonly has an emissivity of less than 0.7.
What this means is that it's very difficult to get an accurate reading if you point an IR thermometer at metal cookware. Even if it's black cast iron you'll get too-low readings from a cheap IR thermometer that assumes an emissivity of 0.95, and if your cookware is shiny stainless steel, you'll have no chance.
The third confounding factor is that when you're not reading the temperature of the actual object - and if you're pointing your thermometer at a shiny stainless saucepan with an emissivity of 0.1, you're pretty close to not measuring the saucepan's temperature at all - you can easily be mainly reading the temperature of something else whose mid-IR emissions are reflecting off the actual object. Essentially, you have to treat all metal objects, in particular, as if they're plated with mirror-polished chrome, and think of what you'd see reflected in them if that were the case.
You can minimise this problem by always keeping the thermometer's line of sight as close as possible to perpendicular to the surface of any low-emissivity objects, but even this won't help much if the object is curved, like the side of a saucepan. For reflective low-emissivity targets, a perpendicular shot will mainly tell you the temperature of the thermometer itself.
(If you want to use your IR thermometer to find hot spots around your car engine, or help you tune a tiny model engine with better thermal resolution than you can get from the spittest, you're not going to get good numbers by shooting the bare metal. A spot of matte-black paint or chalk on the head ought to give you decent results; high-temperature tape made from Kapton or Mylar won't curl up or melt at model-engine temperatures, but it has very low emissivity with most backing materials. Fibreglass tape might perhaps work, since glass generally has quite high emissivity.)
Water and ice have an emissivity above 0.9 and are opaque to medium- and longer-wave IR, so you'll get accurate temperature numbers if you point your thermometer into a pan of water, even if you can clearly see the bottom of the shiny pan in the visible spectrum. This goes for the water in clouds, too; there's a lot of air with invisible but high-IR-emissivity water vapour in it between you and the cloud, but if you point your thermometer at a cloud and get a reading of 5°C, that's probably pretty accurate.
(Clouds themselves can be seen because they're made of tiny liquid water droplets, not water vapour.)
When you shoot your thermometer at the empty sky, especially at night, you'll probably get the lowest reading that your thermometer can manage - commonly -50 or -60°C (-58 or -76°F). As I've mentioned before, all that's between you and the near-absolute-zero temperature of deep space, when the sky is clear, is air, and whatever dust and water vapour it happens to be carrying. The result is very little mid-IR light, and very low IR-thermometer readings. Even with the whole thickness of the atmosphere between you and space - or, if you're not shooting straight up, considerably more than the vertical thickness of the atmosphere - you'll still probably get as low a reading as your thermometer can deliver.
Digital cameras, by the way, can see near-infrared very well; their sensors are actually more sensitive to it than they are to visible light. (Film cameras are different; film tends to be more sensitive to ultraviolet than visible light.)
For this reason, all normal digicams have an IR-blocking filter in front of the sensor, to stop infrared, generally detected in counterintuitive ways by the differently-filtered photosites on the sensor, from giving all of yourpicturesweirdcolourcasts.
The Alphasmart Dana, which I've written about in the past, is about ten years old now. But it's still quite a brilliant little machine.
Alphasmart are in the portable-word-processor business. Every portable word processor back to the legendary portable TRS-80 has looked much the same; full-size keyboard, letterbox-slot monochrome LCD screen, and power usually from AA batteries, which last a startlingly long time.
Most of these things run some sort of proprietary operating system and only have a few built-in programs that you can't change. The Dana is different, though, because it's actually a Palm III with a keyboard and a wide touchscreen. The screen is only 160 pixels high, like those old Palms, but it's 560 pixels wide. (It also has the standard Palm green electroluminescent backlight, which works well enough but eats batteries.)
Anything that'll run on a Palm III (or IIIx) will run on a Dana, but only specially tweaked programs will use anything but the 160-by-160 middle of the screen. The built-in word processor does, of course, use the whole screen, and makes a dandy note-taker.
Alphasmart made a Dana with Wi-Fi, but mine is the version that lacks it; it has IrDA, though, for what little that's worth. Transferring text to a normal computer really couldn't be easier, though. You can save files to an SD card and plug that into a PC reader, but all you actually need to do to shift plain text is plug the Dana into a computer via USB, whereupon it reports itself as a USB keyboard (like that footswitch thing). Then just make sure you're in some text-edity sort of program on the computer, and press the Dana's "Send" button, and it'll "type" out the contents of your document. No special software needed.
The "typing" isn't terribly fast, so this isn't very practical for transferring a large document. But for everyday note-taking and journalism and such, it's great.
[Update: If you've got a Dana but no software for it, I mirrored a few files, including the stock software bundle.]
Oh, and the Dana also charges through the USB cable. Danas come from the factory with a plugpack charger as well, but if you're often near a normal computer you won't need one. (Note that the Dana won't charge from a power-only USB socket, like you get on those gizmoes that convert mains power or a car cigarette-lighter socket into USB power.)
I was moved to write this post by three things. One, the Dana deserves to be more widely known. Two, there are currently quite a lot of affordable Danas on eBay, as we'll see in a moment. And three, I am avaricious. I'm signed up for eBay's Partner Network now, and so can get a few pennies when people click on my links to said Danas.
Here's an eBay search that finds, as I write this, fifteen Dana auctions, some of which have several units available. (The search is supposed to "geotarget" to international eBay sites, but doesn't seem to be doing it for me here in Australia, so here's the same search on eBay Australia, here on eBay Canada, here on eBay UK.)
This seller is probably the one you want. They currently have two multi-item Dana auctions running. This one has six units, without batteries or a stylus, for only $US19.99 each; international shipping would more than double this, but it's still a bargain. And this auction is for "more than 10" Danas, this time with a stylus but still without batteries, for only $US24.99 each. Presuming these Danas do actually work, you really can't go wrong for that price.
The lack of a battery is a bit of a nuisance. When new, you see, the Dana came with a rechargeable battery pack which sits in the AA-cell battery bay but connects with a little two-pin plug, not the contacts on either end of the battery bay. These used Danas don't come with that battery pack (because it's no doubt long since worn out), so the easiest way to power them is with three alkaline AA batteries.
You can run a Dana from rechargeable AAs as well, but it won't charge them if they're not connected like the original battery was. And, just as with the Palm III, taking the batteries out of a Dana for more than 30 seconds will cause the internal memory to go blank. (This isn't actually a big deal unless you've installed your own applications or saved stuff in the internal memory, as opposed to an SD card.)
I made a new battery pack for my Dana by soldering up three low-self-discharge NiMH AAs, and stuffing them into the battery bay. My three AAs with soldered-on tabs connecting them together are bit longer than the original battery, and wouldn't fit in the bay, so I did a bit of butchering that has made my Dana unable to run from normal AAs any more. (There is a better way I could have done this.)
But my Dana does charge via USB, which, I repeat, is really neat. As is just about everything else about this thing. And if you don't want to monkey around with battery-pack building, you can just chuck some alkalines in it and go.
(If you'd like to know more about the Dana, you can download the PDF manual from Alphasmart here.)
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