Some of you may be aware of a guy on eBay called Echowzh (Laboy) selling glassware out of China. I noticed his auctions a long time ago, but already
had most of the things I would have been buying from him.
I did notice he was selling ground thermometers rather cheaply and, when my more expensive Ertco thermometer gave up, I thought I'd give him a try. A
ground thermometer combines a number of glass and equipment making problems because he has to fill it with mercury, get the taper right and the scale,
making me feel it'd be a good test of how well he might be able to make other things.
I should point out straight away, the guy has quite a lot of positive feedback on his account. He was selling the thermometers as 75mm immersion,
whereas I wanted them to be 25mm. I asked and he replied within a day or two saying that was fine and to add a note when paying. That is something the
bigger brand names frequently do not do. They either take weeks to reply or don't bother.
At $15.50 each (about £10) they are considerably cheaper than any well known brand. I would be expecting to pay at least £40 for
one from anywhere else and they're usually £60 to £80.
At that price, I was going to pay it if only to see it. For £10, it is entirely unrealistic to expect the same level of quality from it as something
almost ten times that (I get annoyed at the guys who expect import mini lathes to equate to a $15k Monarch; clearly the Monarch will be better, and
fk'ing expensive too!).
I paid on the 30th of November. He took them to the post office (in China, tracking them) on the 11th of December and today, the 21st of December, in
the UK (straight through Customs without stopping)....
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Loads of fluffy stuff
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Excellent, two massive spliffs for Christmas!
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OOoooOOOooo what's it going to be like!!?!?!?!
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Quick look at the bulb and cone, looks okay
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The scale has been etched into the glass somehow, but the pigment wiped over it doesn't seem too intent on staying put
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I'm feeling all art deco'y on this vibe man.... It seems the cone has been formed by warming the glass and squeezing it together perhaps, to buldge it
out. Hence the background of the scale becoming a swirly pattern in the grind. It is in the grind however, not poking out the sides
of it, creating a corrosion issue. The cone may look warped in the photo. That is actually a fault of the camera, it's a £120 pocket camera and the
fish eye effect is a grinding error on the lens it's self.
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Sat next to the far more expensive Ertco thermometer. Made in Germany, naturally...
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The Ertco people seem to have taken a different approach and encapsulated a normal thermometer within a thermowell.
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I think this is how they've done it not only due to the lack of swirly artwork in the cone but also because the bulb is burst, yet the mercury is
still sat in there, even under vacuum; so there must be two layers of glass in there or it'd have all shattered and emptied out. There are black lines
running longitudinally along the stem, which will be the interface between the two pieces. And it makes a 'twangy' sound when flicked, the inner bulb
rattling against the thermowell. There are splodges of mercury in the interface.
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Echo's modification of the order to 25mm immersion means it does actually fit a 25mm immersion socket.
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Virgin grinding needs lubrification! Looks nice and clean, no gross mess ups. The surface finish could be a bit finer, but it's not rough. I've seen
far worse.
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Slight scuff marks on the stem from grinding. -0.1%. That's a bit mucky, but I've seen faint traces of joining problems (microscopic bubbles) even in
the really expensive glass.
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That pigment's getting out of there. We can consider that a none starter, as it's pretty much gone just in the space of time it's taken me to take
these photos.
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I tried fitting the thermometer into some seriously pricey glass with a small dab of grease and, giving it a spin, couldn't see any voids running
lengthwise. On removing it, I noticed this faint band (look to the left of the pencil tip, then the right). That could be an indication of the taper
not being dead on. http://img408.imageshack.us/img408/3530/img0149wh.jpg
In that the gradient is slightly off, but it is concentric (the band runs around the circumference in a perfectly straight line). I tried adding a
touch more grease and it disappeared. Not perfect but the majority of it sealed with barely any grease, and it is mainly the concentricity that is the
major issue. If that was off, there would be a gap running along the entire length of the taper, making it a cronking POS for anything involving
pressure differentials. As it is, that'll work fine.
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Into ye olde still head... looking decent in terms of sealing.
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I'm going to check the 100C mark by distilling some deionised battery water through this m'ere vacuum jacketed vigreux column.
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That's not going any higher, it's 99C.
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That's the air pressure today according to my weather station (there are a series of docks within a few hundred meters of my house, so I am at sea
level). The local observatory says the air pressure is 1017.7 mbar.
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Into some ice!
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Next one at the BP, slightly under 99C.
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Note how the scale on this thermometer is not lined up with the white background.
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Crickey! That's a bit much. I actually had a photo of this at 0C in the beaker and was wondering if I'd made a mistake. I redid the test with the
other one in the beaker at the same time (reading 0C) and this one was still giving a good few degrees positive of 0. There's an issue with the
zeroing there. Still, I doubt many people will actually use these for 0C distillations.
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Grinding
I'd call that okay. It'll be fine under vacuum and is nearly as good as the branded glass. It'd only need to be better for genuinely demanding things,
like bonefide anhydrous work (septums, lockable syringes et al). Bits of grit, and shite et al, would account for a leakier taper than any gradient
error on this.
Accuracy
It's definitely off, no doubts. Ground thermometers like this are usually used for distillations and will be around 100 to 200C. They both gave 99 for
boiling water, which isn't too bad. Provided the error is linear and you have some good references to check it against, you could account for the
scale error by producing offsets.
The importance of the scale being highly accurate also depends on what precisely you are doing. For many distillations, simply knowing the band to
within 10C will allow you to be reasonably sure you are removing the product you intended to get as there will be significantly large jumps between
many of them. If the mercury is not moving, it is a solid fraction, regardless of the temperature being read off.
If you are running a vacuum distillation, something ground thermometers are good for, and are trying to get an absolute temperature, I can give you a
prime example of other errors.
His thermometers have given me an error of 1C at the boiling point of water under 1 ATM of pressure.
Imagine you are instead distilling a high boiling material under vacuum, one that boils at 186.3C under 1 ATM. You reduce the pressure and it begins
boiling at 99.3C when it should be 100.5C. Even with the best thermometer around, it would only require your pressure gauge to be wrong by 2.1 mmHg to
recreate the mistake. That's 0.27% error in the pressure, not a lot at all. If your pressure gauge is on the other side of a condenser, it may not
actually be reading the pressure the boiling material is exposed to anyway.
Aesthetics
Certainly not winning any sashes in the beautiful ass pageant! But that's not what scientists are interested in right? It's all about the personality,
and numbers... "Hey baby! I got a triple A on my grade sheet!"
I don't mind the weird swirly thing in the cone, but there are two practical problems on the finish.
The pigment rubbing out does make them harder than they need to be to read.
And on that point, the scale on one thermometer is not directly in front of the white background.
I expect I can replace the pigment with something else. But, with it being engraved, I might not even bother with that.
Buy it again?
For the money they're okay. It is painful buying the branded ones, even with their higher quality, when the bill rolls over a hundred for two of them.
You can see how little it takes to mess one up given that the bulb on mine is still intact but shattered internally.
With this being a fairly difficult item for him to get right, I suspect his normal glassware is of decent quality.
I have spent many, many years and so many hours I've lost count, and a lot of money (be a few thousand by now), searching out bits of glass and
waiting months for bits I was after to appear. For the guys who don't use it at least once a week, who haven't had much practical experience or are
short on cash, you should check out Mr Whizzy.
What I have seen thus far says, it is not the best, but it is also not junk. And it is cheap.
[Edited on 5-23-2013 by Polverone]peach - 21-12-2011 at 16:31
I spent a while wondering how he might have calibrated these.
Against boiling water, ice, room temperature, a few of those?
I decided the likely candidate was measuring from the top of the cone and laying the scale at a set distance from that.
What's interesting about that is that one reads degrees incorrectly at 0, one is fine at 0, yet both read about the same at the BP of water.
Which must mean the capillary or scale is slightly none linear.
Or he's done them at the BP of water and the scale or capillary is slightly off.
My neighbour spent many years of his life working at a local factory making special thermometers and insisted we all got up from dinner to watch a
program about building thermometers. He was rendered jobless when the entire factory shut down. I mentioned I was interested in glassblowing to him at
one point. He wasn't too impressed. I have also looked at applying for a job with QuickFit. The wage for a glassblower is about £16k (barely minimum
wage), with previous experience.
[Edited on 22-12-2011 by peach]Lambda-Eyde - 21-12-2011 at 16:37
Nice of you to do this, Peach. I always appreciate your threads, especially the pictures. Good job!
I'm in the market for a 14/23 76 mm immersion thermometer, anyone know where I can get that for a reasonable price? I hate those americans for
inventing the 10/30 joint... Not to mention the 10/18, what the fuck is up with that?
[Edited on 22-12-2011 by Lambda-Eyde]peach - 21-12-2011 at 17:04
No problems.
I don't know why the US guys use 10/18 and 10/30 joints. That is odd.
The 10 sized ones are practical in terms of the really small glass, rather than having a big 14 sized thing for the thermometer. Mercury thermometers
already take a lot longer than digital thermometers to warm up. Having a big chunk of spurious glass attached only slows that down.
I have been wondering about making my own jointed thermometers, but digital ones with platinum elements.
They'd probably cost about as much as the mercury ones, but be much harder to break, warm up quicker, be adaptable, could data log and have a nice big
display that could be read from across the room. And have a known tolerance on them.
I'd need to buy some bits and pieces and speak to the local CNC people about that first.Panache - 21-12-2011 at 17:13
I hate those americans for inventing the 10/30 joint... Not to mention the 10/18, what the fuck is up with that?
[Edited on 22-12-2011 by Lambda-Eyde]
i concur, although taking a good system and making it shit is hardly invention.
guess the thread's ok also peach, lol, nice job, take a sick day did we.
And merry christmas!!Arthur Dent - 26-12-2011 at 11:27
I'd love to get a ground glass thermometer, I only have standard thermometers with a rubber boot/ground glass adapter. So accuracy isn't perfect but
it's a heck of a lot less expensive than the lab catalog stuff. I do have a bit of glassware with the ground glass thermometer ports that I have never
had the pleasure of using...
I'll seek out that Echowhiz fellow and try it out. Many thanks, sir Peach, for your excellent review!
Robert vulture - 26-12-2011 at 15:57
That's good quality considering the price. Could be that the 100C wasn't calibrated at sea level (there's a lot of mountains in China), but that
doesn't explain the 0C error. Anyway, if you're distilling something at 0C your vacuum is too high anyway and you need to bleed.hissingnoise - 27-12-2011 at 04:47
It sure beats wrapping metres of teflon-tape around them shanks!
Funkerman23 - 17-5-2013 at 10:20
After receiving my order today of these and other bits of glass I wanted to give a newer comment on these. Just like peach both of mine( I ordered
two) when used to boil water read 99 degrees. no amount of waiting significantly changed that. However when put into an ice slush the both, despite
having slightly different sized mercury bulbs, read just a hair above zero degrees.with the current air pressure at about 1019.63 millibars water
should boil at 100.194. Some slight improvements in temperature readings possible but not much has changed since peach reviewed these. the coloring
was almost completely gone from mine as well but with luck these will and should work for my current needs. EDIT: well this is rather interesting..the
thermometer has something inscribed on the other side of the shaft. My thermometers where made by Synthware.
[Edited on 18-5-2013 by Funkerman23]Organikum - 18-5-2013 at 01:21
High quality thermometers are still very cheap on german Ebay, its GDR but those were and still are top notch.
With little time and patience you get everything from high precision to Contact-thermometers. And as much I like to buy chinese, in this special case
I would prefer the GDR made ones as they are really good.
Shipping to the US is no issue with such a small item it will cost less the 3€.
