Hi,
I have several crystallising dishes with no markings on them. Not sure if they are made out of borosilicate glass or regular soda lime glass. I bought
them over the years at few occasions. Too long time ago to remember what is what. At least some are borosilicate, but not sure if all.
More useful if they are borosilicate for obvious reasons.
Even if they are made out of soda lime glass they are still very useful therefore I do not want test them by heat stressing.
Is there any non destructive way to determine type of glass ?
No NASA lab equipment available
Just average+ amateur chemistry/physics lab and kit.Twospoons - 7-12-2024 at 21:47
Useful info but I think hardness test on glass will be destructive. Also how can you test that at home without one of those fancy rockwell hardness
testing machines?Deathunter88 - 8-12-2024 at 21:04
You can tell the color difference very easily at the rim. Soda-lime is a blue-teal-greenish color, whilst borosilicate is a pale straw yellowish
green. Just compare it side by side with something you know is soda lime.
[Edited on 9-12-2024 by Deathunter88]Texium - 8-12-2024 at 22:22
You can tell the color difference very easily at the rim. Soda-lime is a blue-teal-greenish color, whilst borosilicate is a pale straw yellowish
green. Just compare it side by side with something you know is soda lime.
While this is often true,
it is not a guarantee. The green tint that’s most common in soda-lime glass is caused by iron impurities, which are not an intentional, necessary
part of the process of making soda-lime glass. So it’s perfectly possible to have soda-lime glass with little or no green tint, but usually it’s
made from cheaper, often recycled raw material, so iron, being pretty ubiquitous, is almost always present. This doesn’t matter since it’s mostly
used in applications where low cost is more important than quality and appearance.
On the other hand, borosilicate glass can have a green tint if there is iron present in the batch, but borosilicate is always made from new raw
materials and likely draws from higher quality sources due to its high value applications.
It’s rare, but I have seen several examples of soda-lime glass that look like borosilicate, and a couple cases of greenish tinted borosilicate.Deathunter88 - 9-12-2024 at 02:10
Yes, but sometimes in home chemistry we need to go by the "if it quacks like a duck" methodology simply because we don't have the resources to do it
the "right way". In my experience it’s rare for boro glass to have more a green tint, so he can almost certainly rule out his glass being boro if it
does have one.
Another easy test is to check the refractive index. Boro glass just happens to have the same refractive index as vegetable oil or glycerin, so if you
submerge the piece into a container of the liquid it should essentially vanish. Just look up "how to make glass disappear" on Youtube for more info.
I'd say if his glass passes both the eye test and the refractive index test, he can be confident it is boro glass. Maybe just don't use it for boiling
concentrated nitric acid.
[Edited on 9-12-2024 by Deathunter88]
[Edited on 9-12-2024 by Deathunter88]Texium - 9-12-2024 at 07:37
I agree it’s a useful heuristic to know, and if it is greenish like typical soda-lime glass, I wouldn’t risk using it. I just wanted to make sure
that the information being presented was accurate. The way you worded it made it sound like you could be 100% confident in the type of glass based
only on the color, when in reality it’s probably more like 95%. I know it’s an edge case, but I wouldn’t want it shattering on them if it turns
out to be unusually yellowish tinted soda-lime glass.
The refractive index test should be more reliable, that’s a good suggestion.
