Does heavy wall borosilicate glass crack easier due to temperatute changes versus borosilicate glass that isn't heavy walled?
Chemetix - 24-3-2018 at 19:22
In general yes! LearnedAmateur - 25-3-2018 at 01:21
Yes, glass is a mild insulator (I’d say between that of plastics and metals) so it takes longer for heat exchange between the nearest and furthest
surface. This basically means that there will be a higher temperature gradient between the two surfaces with thicker walls, and that gradient is what
causes glass to crack because of thermal stress. If you treat heavy glass like any other piece though, you should be fine - just don’t go
immediately to hitting it with a direct flame, use a gauze or at least heat outside of the flame for a minute or two first.RawWork - 25-3-2018 at 05:51
According to Handbook of Inorganic Chemicals: "Quartz is an excellent insulator. It does not break under temperature changes because of its low
coefficient of expansion. Fused quartz transmits ultraviolet light."
So use SiO2 glass. I doubt that any other glass has lower coefficient of thermal expansion. That's reason which determines will something break.
Unlike LearneAmateur said.unionised - 25-3-2018 at 06:17
Quartz is a great insulator- for electricity.Tsjerk - 25-3-2018 at 06:50
But starting to make thick wall glassware out of quartz seems a bit pricey.
Usually thick walled borosilicate is not meant to be heated anyway. Morgan - 25-3-2018 at 07:28
It's too bad someone couldn't make something intermediate between borosilicate and quartz without the high price, that is something more heat
resistant - say add just a little more SiO2 to a boro mix if possible.Yttrium2 - 25-3-2018 at 10:53
Heavy wall is used for vaccuum applications, correct?
If it has the same thermal coefficient of expansion, and is borosilicate glass, why isn't it just as resistant to cracking as thinner walled material.
Why is everyone going off to talk about quarts?
(Sorry I posted this here. Something happened where I saw only certian forum sections po up and I figured I was banned)
[Edited on 3/25/2018 by Yttrium2]unionised - 25-3-2018 at 10:58
Heavy wall is used for vaccuum applications, correct?
If it has the same thermal coefficient of expansion, and is borosilicate glass, why isn't it just as resistant to cracking as thinner walled material.
Why is everyone going off to talk about quarts?
Thin walled glass heats more evenly so it's less likely to crack when heated. Nobody but you wis is talking about quarts.
Quartz is stronger and has a lower thermal expansion so it's better for thick walled stuff.
It's much more expensive.RawWork - 25-3-2018 at 11:11
Yes, "low", not "same" (even) coefficient. Because Si is more common element than B. Also I believe Na, Ca and others could be somehow removed from
glass as they are minor. Or why not make SiO2 glass? There are quartz heaters where I see red hot filament of iron and quartz around it. Very
resistant to temperature.
It's true that thicker something is the more resistant to pressure or temperature changes it is. That's why lead glass is used in CRT.
Why not just use CRT? They are now almost free. They are resistant to pressure and temperature changes enough. https://www.youtube.com/watch?v=qp6tNaUvfNIunionised - 25-3-2018 at 11:22
They do make silica glass. It's refereed to as fused quartz, and it's what people have been talking about here.
The problem is that it's expensive- because it is difficult to work with.
It is not true that thicker glass is more resistant to temperature changes- You have got it backwards. Thick glass is more likely to crack with
thermal shock.
Lead glass is a good electrical insulator which helps, but the real reason they used it in CRTs was to block Xrays. Yttrium2 - 25-3-2018 at 11:52
Ultimately, I'm wondering which distillation kit to go with.
There is a seller on Amazon called dinglab, but it's heavy walled glass and a few bucks extra, however everyone is ranting and raving about there kit.
Except the distillation adapter, I guess it wasn't made to well -- the plastic pieceYttrium2 - 25-3-2018 at 12:30
Ahhhh I'm having a hard time deciding which distillation apparatus is best. I'm thinking one with a 3 way adapter that has a seperate thermometer
attachment. Can someone provide information on the chinese distillation kits? Are they virtually all the same? Cause I've noticed subtle differences
with the 3 way distillation adapter, and how the thermometer comes hooked up. Is there a difference in packaging? Which ones should I go with/avoid.
also, can someone provide information as to when and why heavy wall glass is desireable? Does it greatly increase risk of a flask cracking, or not so
much with the borosilicate glass? Yttrium2 - 25-3-2018 at 12:32
Maybe I should just get a 250ml erlenmeyer, a stopper, and a couple pieces of very long glass tubing... It would save a bit of money, and would likely
do just as good of a job for most applications (I'm guessing) aga - 25-3-2018 at 12:44
Just get the cheap stuff - works fine for everything i've tried.
The two events that destroy my glassware are Shipping and Cleaning (mostly cleaning).
Never lost a single glass item during an actual experiment.unionised - 25-3-2018 at 12:51
If you plan to use some sort of heating bath (and you should) then thick walled stuff should be fine.
I haven't seen the kit you are talking about, so I can't comment.
Perhaps others have.Yttrium2 - 25-3-2018 at 13:35
the cheap stuff as in a single flask with a really long glass tube, or the cheap stuff such as the cheap distillation apparatus? Ehh
was thinking of getting the cheapish one with the nice 3 way distillation adapter that has the thermometer and adapter as a separate piece from the 3
way distillation adapter. I can get that and a claisen adapter (so I can do steam distillation/maybe more) for around 36$ with shipping.
I've gone through a few kits during my time, its nice to see the prices dropping especially because of the way I go through kits
[Edited on 3/25/2018 by Yttrium2]aga - 25-3-2018 at 13:39
Not seen you post anything about what you've done.
Photos are always nice.
Edit:
The cheap stuff i was referring to was a 200 or 300 ml Liebig condenser and a disty head - the one that is straight with an angled arm, all
ground-glass 24/29 joints.
[Edited on 25-3-2018 by aga]Sulaiman - 25-3-2018 at 13:40
I agree with aga that damage during shipping/storage/cleaning/drying is much more likely than damage during an experiment.
So a little care during heating and cooling using heavy wall flasks may be best, especially if vacuum is planned for,
but most of my stuff is cheap Chinese wg48 - 25-3-2018 at 13:43
Lead glass is a good electrical insulator which helps, but the real reason they used it in CRTs was to block Xrays.
Lead cannot be used to block x-rays in the front plate of colour CRTs as leaded glass darkens due to the effects of the electron beam. Barium and
strontium are used instead.
Leaded glass is used in the rest of tube and incidentally in light bulbs and florescent tubes because of its lower softening temperature and
suitability in making glass to metal seals aga - 25-3-2018 at 13:44
Funny. I was trying out a vacuum distillation today and it was a nightmare.
At 100mBar it foamed like that geyser in yellowstone park that Yogi bear used as a bidet.
Bleeding PITA the whole thing.
In the end i got mad with the liquid and boiled it down in a beaker instead.
Got to 10% of the original volume with zero foaming.RawWork - 25-3-2018 at 13:54
Leaded glass is used in the rest of tube and incidentally in light bulbs and florescent tubes because of its lower softening temperature and
suitability in making glass to metal seals
Also because of resistance to extreme pressures.aga - 25-3-2018 at 14:02
Does any amateur buy cheap glass and mess with Extreme pressures ?
No. Why not ?
Cos they all got killed during the experiment by Big shards of high-speed glass.
Evolution kinda took care of those types of amateurs, mostly.
Not many amateurs dabble in high pressure, apart from the hydrothermal nutjobs, and they use steel.Yttrium2 - 25-3-2018 at 14:19
Unfortunately I've had to throw away my kits, or return them.
I'll be on my 3rd or 4th
Things I've done are
fractional distillation of ether, to get the ether from a can of starting fluid
fractional distillation of ethyl alcohol
tried making ether, but wasn't measuring temperature in Celsius and I forget what happened after that, I didn't take good notes. If memory serves me I
didn't go on with the experiment because of the high heat needed, for some reason. Think it was something coupled with the fact that I didn't have a
pressure equalizing addition funnel...
I really haven't done too much.
When I was younger my parents freaked out when they saw lead balls, mixed with the ingredients for making black powder. They thought I was going to
make a claymore, or something. That was one of the first times I had to put my interests and enthusiasms on halt.
I have a very limited sense of what I can do with a simple setup, I should probably be focusing more on math and getting further ahead in school, that
way I can build more ideas but right now I guess I'm kind of burnt out (stressed out) and really really wanting to get this distillation kit.
There is a bit of a spiritual element to it for me. It gets me excited, I'll be able to use that excitement towards getting ahead in school... I
resonate with the fact that early distillations were done by alchemists trying to transmute base metals into gold. I too am trying to perform a
distillation, though it might be more so a matter of distillation of spirit. Looking back over the years, trying to find what I lost. I like the look
of the alembic, the pelican, the retort, or whatever you want to call them. I do see life and things as a spiritual journey. There is a substance I
can't capture nor define, yet. Sometimes I have it sometimes I don't, but when I do I fly. Like the early alchemists I too am trying to put things
through a bit of a crucible, trying to find a bit of spirit. Somewhere. Needless to say, I do take chemistry, school, and religion very seriously.
zed - 29-3-2018 at 15:49
Ummm.
I have purchased some Chinese Glassware recently.
Looks pretty good actually. Sturdy enough, but a little wonky. As in Cat-In-The Hat-ish.
It lacks the perfect symmetry of old-time American glassware. But, perhaps I mis-remember.
Might have been, in my wild youth, I was less discerning regarding symmetry.
I've broken my share of glassware. Sometimes, I am an inattentive maladroit. Moreover, a fair amount of my glassware, seemed to break itself.
Star cracks mysteriously appeared, in round bottom flasks. From Whence? It never mattered really. It was OK. Then suddenly, it was trash trash.
Buy another one.
If you have some budget, The Chinese can be very helpful. For I few hundred bucks, you can set yourself up with pretty nice array of glassware.
Seriously, American Glass with ground glass joints, was always pretty expensive. A very small kit, used to cost hundreds. And, that would be in the
BIG dollars of 50 years ago.
Nowadays, for a few hundred, you can put together a pretty decent collection of gear.
I've had decent luck with Deschem. From order, to delivery, from China to the US, about a week. Highly rated.
Next time out, I'll try Nanshing. They have a nice looking kit, for not very much.
Moreover, they seem to be receptive to allowing some substitutions.
[Edited on 30-3-2018 by zed]Yttrium2 - 30-3-2018 at 16:47
There is a Chinese distillation kit made of heavy walled glass, on Amazon, with great reviews, which is why I'm asking.
It's main use is for intensive vacuum applications, correct?
[Edited on 3/31/2018 by Yttrium2]zed - 31-3-2018 at 16:02
Yttrium2,
I don't know the seller. Might be great stuff. Might be fake reviews.
I've got trust for what the guys here tell me.
Though I will attempt to visit the site.
Ummm. I took a look. More expensive than Deschem, by a lot.
When it comes to vacuum, I'm sure heavy walls might be useful. But, for a smaller flasks, I don't know how much difference it makes.
The bigger the flask under vacuum, the stronger its walls must be. At a certain pressure/vacuum... depending on the size of the vessel, you must
switch to a metal vessel.
Also of note, I like flat bottom vessels. Much easier to work with. Not however, as strong as completely spherical vessels. An arch reinforces
itself. Not so, that flat bottom.
[Edited on 1-4-2018 by zed]Fyndium - 2-8-2020 at 07:14
I received a chinese desiccator recently. I suppose the small inclusions and casting errors do not matter when applying vacuum?
They appear like cracks, but they are only on the surface of the glass.
[Edited on 2-8-2020 by Fyndium]outer_limits - 2-8-2020 at 08:29
I wouldn't apply vacuum to a vessel that has visible glass breaks
[Edited on 2-8-2020 by outer_limits]Fyndium - 2-8-2020 at 09:34
Please note that these are not cracks or breaks but more like casting marks.outer_limits - 2-8-2020 at 10:28
I wouldn't use it with vacuum still, I would rather contact the supplier and try to get another one without such things.
I have no expertise in materials endurance and I don't know how it affects the glass durability but I doubt that has no effect.
If you want to use it be careful - use something to protect from flying glass in case of implosion. It could be event strong tape which will hold the
glass together.Fyndium - 2-8-2020 at 10:38
I will proof it to high vacuum by wrapping it in stretch wrap and most likely every time I use it because I've got rolls of that stuff. That thing has
a volume of over 5 liters so it will cause a mess if it goes off.S.C. Wack - 2-8-2020 at 10:42
If it doesn't weaken the glass (presumably it does) it says something about the quality. You wouldn't see that on even Brazilian Pyrex.macckone - 2-8-2020 at 12:54
Even good looking vacuum chambers can implode.
The best way to tell if there is a problem is by polarized examination.
Stresses stand out.Dr.Bob - 5-8-2020 at 16:41
Thick glass will withstand washing and handling better, terrible with direct flame or other harsh heating.
I have been doing chemistry for 30 plus years, and have never experienced or seen any flask break due to just vacuum. Even the older thin Pyrex round
bottoms that are 20 plus years old don't break due to vacuum, unless hit or heating under vacuum harshly (like a flame or direct hot surface). I use
a rotovap almost every day, and have yet to break a single flask on one, even though I often use a strong vacuum on it. I also dry flasks on a
vacuum manifold almost every day, none have ever broken under vacuum.
But if they get cracked in washing or moving often, and once they have any crack, even a tiny star crack, they are not safe for vacuum work. I have
used them for (after marking well) for other minor tasks, not important work, like storing material. So the thickness of the glass only matters to
avoid breakage in handleing, thicker is better for handling, but thinner is better for heating.
I have also seen a few flasks broken by pressure as well, but again, typically when hit while under some pressure. I blew a septa off a 3 RBF today
under nitrogen pressure, worst problem is if an addition funnel or condenser pops off due to pressure. (I was trying to canulate a solution from one
flask to another, and only 5-10 psi can be enough to blow off pieces if not securely fastened. ) Had I accidentily hit the flask with a piece of
steel or other glass, it could have easily broken and shattered.
So my advice is don't worry too much about the thickness, any will do, the quality of the joints is much more important, especially if doing vacuum
work. And handle it carefully, and don't use cracked glass for vacuum or critical work. And don't ever heat glass with a flame unless you really
know what you are doing, it is very hard to do without shattering the flask. Practice with water or something safe, not organics or acids. I've
seen people heat acids to distill with a flame, and that is madness. Safe for heating flammables with a flame, unless in a hood and really safe.
Fires happen, and I have seen some big ones, they grow fast. pneumatician - 10-1-2021 at 15:02
Distilling a solid salt at 360 ºC and... horrible "CRACKKKKK" :-O
new item, very fat glass, used in lower temps 2 times, 90€ in the trashFyndium - 28-1-2021 at 23:43
I have not applied direct heat to any glass since I started chemistry again a year ago, I exclusively use some sort of heating bath and my go-to has
been CaCl2 up to 150C. I ain't got a heating mantle (yet). Only exception was when I distilled sulfuric acid, but I used a flask which I determined I
was ready to lose.
It appears that you used an intensive heat source to reach that temp obviously, which led to sufficient thermal stress to crack that reactor. Large
opening would allow easier application and removal of solids, but apparently reactor glassware tends to be thicker.
Getting much above 200C with heating baths seem to be a bit tricky. People have used sand or salt baths for these, I haven't tried but apparently for
a couple of reactions I've got to see if they could be heated effectively to above, since any oil bath seems to start smoking excessively even much
below 200. Steel shots afraid me because they have very high thermal conductivity, which could stress the glass.
Perhaps a combination of pre-formed glass or ceramic wool mantle placed into a pit of steel could provide good and stable heating for high temperature
reactions.
