SuperOxide
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How to tell borosilicate from non-borosilicate glass
I have a pretty decent amount of glassware, a lot of it I buy from Biotech Bargans and they buy it from colleges or companies that have labs and are
shutting down or getting rid of excess glassware. A lot of what I get is Pyrex, Chemglass, Ace, Laboy, etc. And I try to steer clear of anything
that's soda-lime. I know the difference between PYREX and pyrex. And according to this article, you can tell the difference between borosilicate and soda-lime by the color of the edges:
| Quote: | | If you have a dish at home that you want to test you can also try just looking at the hue. If you look at the edge of a dish and it is made out of
soda-lime glass it will be a blueish-green hue. If the glass is Borosilicate then you should not see any color. |
So this was my quick test that I would use, but the problem is - A lot of the PYREX stuff I have (some of it was new, some used) has that green color.
And I tested some of this by cranking my hotplate up to pretty high temperatures and then putting the glassware on it, filled with cold water to see
if it would break (as well as some other tests that break things like salsa jars pretty easily), and I haven't had any of them break.
I've never had any of these break or crack during any experiments/synthesis I've done, and I have definitely abused some of it quite a bit.
I posted some pictures to an Imgur album and put captions to each one. https://imgur.com/a/XEUXJB7
Im hoping someone can make some of these make sense. I could maybe believe that some of my Pyrex is fake, but all of it? No way. Some of it is from
Germany, some from BiotechBargans, some from other sellers.
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Twospoons
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The green tint is from traces of iron in the glass. No reason why borosilicate couldn't have that too. I know you can get iron free soda-glass ( its
just costs more), so it would not have that tint.
Borosilicate should be harder than soda, so there is always the scratch test.
Helicopter: "helico" -> spiral, "pter" -> with wings
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Chemetix
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All the glassware you have is borosilicate. There is practically no one making soda glass beaker like the ones you have. The decals seem like older
Kimble glass at least on one item that I can make out, but that's circumstantial.
Really, the only scientific glass that commonly isn't borosilicate is burette or other volumetric ware. It's termed AR glass which is a type of soda.
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SuperOxide
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Quote: Originally posted by Twospoons  | The green tint is from traces of iron in the glass. No reason why borosilicate couldn't have that too. I know you can get iron free soda-glass ( its
just costs more), so it would not have that tint.
Borosilicate should be harder than soda, so there is always the scratch test. |
I see, that makes total sense. Thanks!
| Quote: Originally posted by Chemetix | | All the glassware you have is borosilicate. There is practically no one making soda glass beaker like the ones you have. The decals seem like older
Kimble glass at least on one item that I can make out, but that's circumstantial. |
Right, but it's not like that doesn't happen. For example, I think in that Life After Detonation thread he said he was using a "Pyrox"
soda-lime beaker without realizing it.
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Tsjerk
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You can easily test what you have by boiling some water in the beaker and cooling that in an ice bath. Soda lime can't handle anything more than 30 -
40 degrees heat gradient over a certain distance. This gradient you can easily reach with boiling and freezing water while borosilicate should easily
handle these gradients when not thick vacuum glass or something.
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unionised
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I think Pyrex cookware is available in a range of colours.
The traditional way to tell soda glass from borosilicate was by refractive index.
Pyrex "disappears" in glycerine.
Not very useful if you are looking at a whole beaker, but handy if you are glassblowing and have lots of tune + rod.
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Dr.Bob
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I have seen borosilicate with clear, green, blue green and other tints, as stated, it is the iron content, which does not change the temperature
stability. There are a few simple density and refractive index tests for boro verses soda lime, but almost all lab glass is boro. I'd guess there
is some way to see with a UV-VIS or some other simple test, but rarely done.
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Twospoons
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Reading around I found the density and refractive index ranges for boro and soda overlap. Only distinctive diff I could find was hardness : 7 for
boro, 6 for soda
Helicopter: "helico" -> spiral, "pter" -> with wings
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yobbo II
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Soda glass will fluoress under UV light a bit.
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SuperOxide
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I think what Twospoons and Chemetix mentioned is pretty convincing. The color is just from some iron contamination (which when I Google it, seems
pretty accurate), and it would be very unlikely that anyone make such glassware in soda-lime, especially the 4 and 6L erlenmeyer flasks.
I was just being paranoid... lol
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Texium
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I think the color thing is a common misconception that has developed because most borosilicate lab ware is colorless, whereas most soda lime glass has
a green tint. Really it’s a correlation-not-causation situation. It’s more likely that higher value borosilicate glass destined for lab ware will
use higher quality ingredients with fewer impurities. Thus, no color.
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Morgan
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Saw this overly high melting point not caught yet.
"Borosilicate glass melts at about 1,650 °C (3,000 °F; 1,920 K)."
" Borosilicate is referred to as "hard glass" and has a higher melting point (approximately 3,000 °F / 1648 °C) than "soft glass", which is
preferred for glassblowing by beadmakers."
https://en.wikipedia.org/wiki/Borosilicate_glass
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clearly_not_atara
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Just get a source of thermal neutrons and measure the absorption cross-section. Borosilicate will definitely be much more avid.
What's that you say? You don't have any neutron sources? Radiation equipment is strictly regulated and very expensive?
Fine, test something boring like the density or refractive index 
[Edited on 04-20-1969 by clearly_not_atara]
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Sulaiman
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I doubt that the sales quantity of 6l flasks would make counterfeiting profitable.
For specifications check the manufacturer's website 
e.g.
Attachment: 4980-6L.pdf (5kB)
This file has been downloaded 124 times
CAUTION : Hobby Chemist, not Professional or even Amateur
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Dr.Bob
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We have borosilicate test tubes in many shades of clear, greenish, and green edges, just depends on the batch and maker. Maybe newer cheap
glasssware might be fake, but older stuff is good, in every case that I have seen. As stated, not a big enough market to make fake Pyrex until China
got into it.
Looks like Biotech Bargans is a pretty good source of stuff. We used to have several places like that, but all have eventually closed or shifted to
other materrials. Most here were thrift stores that got a ton of stuff from a closing science business or such, but now most are closed, so few left
to close now.
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Morgan
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| Quote: Originally posted by Morgan | Saw this overly high melting point not caught yet.
"Borosilicate glass melts at about 1,650 °C (3,000 °F; 1,920 K)."
" Borosilicate is referred to as "hard glass" and has a higher melting point (approximately 3,000 °F / 1648 °C) than "soft glass", which is
preferred for glassblowing by beadmakers."
https://en.wikipedia.org/wiki/Borosilicate_glass |
The actual melting point of borosilicate glass
THERMAL PROPERTIES melting point 1252°C
softening temperature 821°C
(Wikipedia only 400 C off the actual melting point or about the temperature where pure fused quartz melts.)
https://www.imetra.com/borosilicate-glass-material-propertie...
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blogfast25
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I'm not sure what you mean here. This page:
https://www.swiftglass.com/blog/borosilicate-material-focus#...
... also gives the MP as 3,000 F.
Your IMETRA page is full of small errors which don't inpire me with much confidence, e.g. alumina is called 'alumina oxide' and the refractive index
of borosil is stated as "1.471 nm"
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Morgan
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I could have sworn borosilicate glass had a lower melting point than fused quartz. I didn't pay attention to the refractive index topic so yes that
site is probably not a stellar source. Perhaps it was the "partial melting" or slumping I was thinking of and to completely melt Pyrex it is that high
of a temperature.
Here are some other sources.
(see thermal properties chart/melting onset)
"For each property being compared, the top bar is fused quartz and the bottom bar is borosilicate glass."
https://highlyeducatedti.com/blogs/information/thermal-shock...
WHY NOT BOROSILICATE GLASS?
• Material will not maintain its shape if exposed to thermal conditions greater than 450C for long periods of time.
https://rayotek.com/tech-specs/material-comparisons.htm
"It also has a high melting point of approximately 1648°C, making it more heat resistant than regular glass. It is known that above 525°C, the glass
begins to soften and above 860°C, it begins to liquefy." (How confusing)
https://materialshub.com/material/borosilicate-glass/
PRODUCTION AND SPECIFICATIONS OF GLASS WAFERS
Material Properties of Quartz, Fused Silica and Borosilicate Glass (See Chart)
https://www.microchemicals.com/technical_information/glass_w...
[Edited on 23-12-2022 by Morgan]
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blogfast25
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| Quote: Originally posted by Morgan |
"It also has a high melting point of approximately 1648°C, making it more heat resistant than regular glass. |
Highly 'precise' statements of the 'MP' of borosil glass are probably oxymoronic, as it is't crystallin and thus doesn't have a precise MP. That and
the fact that its composition varies somewhat from source to source.
[Edited on 23-12-2022 by blogfast25]
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Morgan
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| Quote: Originally posted by blogfast25 | | Quote: Originally posted by Morgan |
"It also has a high melting point of approximately 1648°C, making it more heat resistant than regular glass. |
Highly 'precise' statements of the 'MP' of borosil glass are probably oxymoronic, as it is't crystallin and thus doesn't have a precise MP. That and
the fact that its composition varies somewhat from source to source.
[Edited on 23-12-2022 by blogfast25] |
Tidbits
"Fused quartz is a solid material at room temperature, but at high temperatures, it behaves like all glasses. It does not experience a distinct
melting point as crystalline materials do, but softens over a fairly broad temperature range. This transition from a solid to a plastic-like behavior,
called the transformation range, is distinguished by a continuous change in viscosity with temperature."
https://www.qsiquartz.com/thermal-properties-fused-quartz/
Quartz vs Borosilicate
https://youtu.be/VbkJ_snSe58
Heraeus states the softening point of flame fused quartz is 1660 C reading from their thermal data chart.
https://www.heraeus.com/en/hca/fused_silica_quartz_knowledge...
"Borosilicate glass not only has good temperature resistance, but good thermal shock resistance as well. Borosilicate temperatures at atmospheric
pressure are up to 500°C for the strain point, while the softening point is over 800°C."
"It also has a high melting point of approximately 1648°C, making it more heat resistant than regular glass. It is known that above 525°C, the glass
begins to soften and above 860°C, it begins to liquefy."
https://materialshub.com/material/borosilicate-glass/
"The softening point (temperature at which viscosity is approximately 107.6 poise) of type 7740 Pyrex is 820 °C (1,510 °F)."
Wikipedia (Borosilicate glass)
Corning® Pyrex® 7740 Glass
https://www.sgpinc.com/materials/borosilicate/pyrex7740-glas...
[Edited on 24-12-2022 by Morgan]
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Morgan
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| Quote: Originally posted by SuperOxide | I have a pretty decent amount of glassware, a lot of it I buy from Biotech Bargans and they buy it from colleges or companies that have labs and are
shutting down or getting rid of excess glassware. A lot of what I get is Pyrex, Chemglass, Ace, Laboy, etc. And I try to steer clear of anything
that's soda-lime. I know the difference between PYREX and pyrex. And according to this article, you can tell the difference between borosilicate and soda-lime by the color of the edges:
| Quote: | | If you have a dish at home that you want to test you can also try just looking at the hue. If you look at the edge of a dish and it is made out of
soda-lime glass it will be a blueish-green hue. If the glass is Borosilicate then you should not see any color. |
So this was my quick test that I would use, but the problem is - A lot of the PYREX stuff I have (some of it was new, some used) has that green color.
And I tested some of this by cranking my hotplate up to pretty high temperatures and then putting the glassware on it, filled with cold water to see
if it would break (as well as some other tests that break things like salsa jars pretty easily), and I haven't had any of them break.
I've never had any of these break or crack during any experiments/synthesis I've done, and I have definitely abused some of it quite a bit.
I posted some pictures to an Imgur album and put captions to each one. https://imgur.com/a/XEUXJB7
Im hoping someone can make some of these make sense. I could maybe believe that some of my Pyrex is fake, but all of it? No way. Some of it is from
Germany, some from BiotechBargans, some from other sellers. |
I received a PYREX (all caps) measuring cup and iced tea pitcher as a gift in the mail today. The pitcher is a light green color along the rim but the
measuring cup has a decidedly blue color when looking at the rim. It's quite apparent.
Here you can see a bowl the company makes in boro with a blue rim.
https://icedteapitcher.myshopify.com/collections/vintage-pyr...
https://icedteapitcher.myshopify.com/products/3lcasserole-di...
https://icedteapitcher.myshopify.com/
[Edited on 24-12-2022 by Morgan]
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Fulmen
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The fundamental problem is that both are very loosely defined terms. But think about it, what are the most likely compositions? It's either going to
be something on par with Pyrex/Duran or something close to window glass, e.g. the cheapest stuff around.
We're not banging rocks together here. We know how to put a man back together.
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