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Protip: You can tell soda-lime from borosilicate by using a homemade polarimeter. [1] Get a pair of polarizing sunglasses, and hold them in front of a computer

Protip: You can tell soda-lime from borosilicate by using a homemade polarimeter. [1] Get a pair of polarizing sunglasses, and hold them in front of a computer monitor at such an angle that the screen looks black. Hold the cookware in between the glasses and the screen. You should now be able to see the screen (see my synchronicitous comment [2] yesterday about the link here to quantum mechanics). If you see a checkerboard pattern, you are holding tempered soda-lime. (The pattern is due to the tempering process.) Soda-lime also has a distinctive greenish tinge when viewed edgewise. Borosilicate is clear. [1] https://arstechnica.com/civis/viewtopic.php?p=2746878#p2746878 https://arstechnica.com/civis/viewtopic.php?p=2746878#p27468... [2] https://news.ycombinator.com/item?id=19406122 https://news.ycombinator.com/item?id=19406122

Camillo 8y ago
Step-by-step instructions: 1. Buy some sunglasses. Make sure they have polarizing lenses. 2. Get a computer monitor. 3. Holding the glasses in front of the screen, rotate them until the angle is such that the screen appears black when looking through the lenses. 4. Make a note of the angle. In this configuration, the combination of the glasses and the screen serves as a homemade polarimeter. 5. Throw all that shit in the garbage. 6. Just look at the glassware edgewise, if it's greenish it's soda-lime.
- colanderman 8y ago
  But using a homemade polarimeter is way cooler.
- loco5niner 8y ago
  You're missing the point. It's fun and is a great way to see an example of polarization in the real world.
jrootabega 8y ago
That's wild, thanks! I tried with a couple of my pieces (although they do say "not polarimeter safe") and they did have some noticeable brightness gradients, though I hesitate to call them patterns. What DID stand out looked like brown scorch marks or stellar jets/magnetic poles. I don't think they were really scorch marks, but it was striking just how brown that tiny area was. Edit: got a picture but it's more of a red and blue interplay than just brown. http://imgur.com/a/0xRlg9D http://imgur.com/a/0xRlg9D Maybe it's the rgb of the monitor. And I have seen similar colors in windshield polarization. It makes more sense if you rotate the glasses and watch the brown and blue flow through the patterns
- colanderman 8y ago
  That's definitely soda-lime. (Judging both by the pattern and the logo.) The reason for that pattern according to the source I linked above is that that is the shape of the air jets used for cooling the glass during tempering. Windshield glass shows the same patterns for the same reasons.
- leereeves 8y ago
  "Not polarimeter safe" is probably a reliable indication of an inferior product. Polarimeters aren't dangerous; they must want something to complain about when someone uses one to prove their product is inferior.
fenomas 8y ago
What does the polarimeter test imply if neither of the described results happens? The glassware in my house doesn't seem to have any noticeable effect on the polarized light; it doesn't get more visible or have any particular pattern.
- colanderman 8y ago
  I am far from an expert, so take everything I say with a grain of salt. But my understanding is that what makes light visible in the polarimeter test is stress due to tempering. E.g. my soda-lime (Pyrex) bakeware shows up very clearly in this test, but my soda-lime drinking glasses do not cause any light to appear in the test (except at their bottom). I unfortunately don't own borosilicate bakeware, so my above description of the effect comes from my linked source. The only borosilicate samples I do have are a microwave dish and a candy thermometer. The microwave dish (which has a rough texture) does show some light, but in a hazy pattern, and much less than soda-lime bakeware. The candy thermometer (which is test-tube sized) shows no light in the test. So if you're looking at bakeware, it's probable that it's either borosilicate or some other type (such as aluminosilicate used in Pyrex Flameware… again just guessing here). If you're looking at drinking glasses, then they're probably just untempered soda glass or crystalware (lead glass).
  - fenomas 8y ago
    Thanks! For what it's worth I was looking at glass bakeware that advertises itself as heat resistant and microwaveable, from a company called Iwaki glass. Googling suggests they make a lot of borosilicate scientific stuff but I couldn't find any info about their consumer products.
code_duck 8y ago
Cool tip about the polarization. As far as visual ID, I don’t know about the borosilicate that was used for a kitchenware, but borosilicate can appear green, colorless or slightly yellowish. It depends on the formulation and impurities in the batch – for instance, iron causes the green color. This varies between Kimax and Pyrex and Duran used for labware and art. One could also distinguish this glass by using the index of refractivity. Glass will disappear when put into liquid with the right refraction. You can make a formula with a refractive index that matches a known glass and then compare. I’d post links but I’m on a very slow connection.

Camillo 8y ago

Step-by-step instructions: 1. Buy some sunglasses. Make sure they have polarizing lenses. 2. Get a computer monitor. 3. Holding the glasses in front of the screen, rotate them until the angle is such that the screen appears black when looking through the lenses. 4. Make a note of the angle. In this configuration, the combination of the glasses and the screen serves as a homemade polarimeter. 5. Throw all that shit in the garbage. 6. Just look at the glassware edgewise, if it's greenish it's soda-lime.

colanderman 8y ago
But using a homemade polarimeter is way cooler.
loco5niner 8y ago
You're missing the point. It's fun and is a great way to see an example of polarization in the real world.

jrootabega 8y ago

That's wild, thanks! I tried with a couple of my pieces (although they do say "not polarimeter safe") and they did have some noticeable brightness gradients, though I hesitate to call them patterns. What DID stand out looked like brown scorch marks or stellar jets/magnetic poles. I don't think they were really scorch marks, but it was striking just how brown that tiny area was. Edit: got a picture but it's more of a red and blue interplay than just brown. http://imgur.com/a/0xRlg9D http://imgur.com/a/0xRlg9D Maybe it's the rgb of the monitor. And I have seen similar colors in windshield polarization. It makes more sense if you rotate the glasses and watch the brown and blue flow through the patterns

colanderman 8y ago
That's definitely soda-lime. (Judging both by the pattern and the logo.) The reason for that pattern according to the source I linked above is that that is the shape of the air jets used for cooling the glass during tempering. Windshield glass shows the same patterns for the same reasons.
leereeves 8y ago
"Not polarimeter safe" is probably a reliable indication of an inferior product. Polarimeters aren't dangerous; they must want something to complain about when someone uses one to prove their product is inferior.

fenomas 8y ago

What does the polarimeter test imply if neither of the described results happens? The glassware in my house doesn't seem to have any noticeable effect on the polarized light; it doesn't get more visible or have any particular pattern.

colanderman 8y ago
I am far from an expert, so take everything I say with a grain of salt. But my understanding is that what makes light visible in the polarimeter test is stress due to tempering. E.g. my soda-lime (Pyrex) bakeware shows up very clearly in this test, but my soda-lime drinking glasses do not cause any light to appear in the test (except at their bottom). I unfortunately don't own borosilicate bakeware, so my above description of the effect comes from my linked source. The only borosilicate samples I do have are a microwave dish and a candy thermometer. The microwave dish (which has a rough texture) does show some light, but in a hazy pattern, and much less than soda-lime bakeware. The candy thermometer (which is test-tube sized) shows no light in the test. So if you're looking at bakeware, it's probable that it's either borosilicate or some other type (such as aluminosilicate used in Pyrex Flameware… again just guessing here). If you're looking at drinking glasses, then they're probably just untempered soda glass or crystalware (lead glass).
- fenomas 8y ago
  Thanks! For what it's worth I was looking at glass bakeware that advertises itself as heat resistant and microwaveable, from a company called Iwaki glass. Googling suggests they make a lot of borosilicate scientific stuff but I couldn't find any info about their consumer products.

code_duck 8y ago

Cool tip about the polarization. As far as visual ID, I don’t know about the borosilicate that was used for a kitchenware, but borosilicate can appear green, colorless or slightly yellowish. It depends on the formulation and impurities in the batch – for instance, iron causes the green color. This varies between Kimax and Pyrex and Duran used for labware and art. One could also distinguish this glass by using the index of refractivity. Glass will disappear when put into liquid with the right refraction. You can make a formula with a refractive index that matches a known glass and then compare. I’d post links but I’m on a very slow connection.