Vintage Pyrex Measuring Cup Borosilicate Vs. Soda Lime Color Difference?
I bought 2 vintage PYREX measuring cups with green text from a thrift store, One large 1 liter and a smaller half liter measuring cup.
I read online that if it says PYREX in all caps then it's made from Borosilicate glass and that if it's lowercase pyrex then it's made from tempered soda lime glass.
What's unusual is that the measuring cups have different color tints to them. the larger one has a more bluish tint to the glass and the smaller one is clearer and more green.
On Wikipedia it's saying that the more bluish one is made of soda lime, but how can that be since it was made before 1998 and says PYREX?
https://en.wikipedia.org/wiki/Pyrex#/media/File:Pyrex_and_PYREX.jpg
Does anyone know what's going on or how I can tell which glass is used in these measuring cups?
Best Answer
The destructive test for borosilicate or not is as easy as fill with boiling water, wait a while for it to heat up, dump the boiling water, fill with ice. If it breaks, it's probably not borosilicate.
On the other hand, any tint is a probable indicator that it's NOT borosilicate, which has a very flat transmission characteristic in the visible range.
If you really want to get into the nitty gritty you can mix up some refractive index matching fluid, submerse the measuring cups, and see if they "disappear" - which seems to be a common means of testing for borosilicate, as it has a different index of refraction from quartz or soda-lime glass.
You can use a known borosilicate to help get the solution correct.
Pictures about "Vintage Pyrex Measuring Cup Borosilicate Vs. Soda Lime Color Difference?"
Quick Answer about "Vintage Pyrex Measuring Cup Borosilicate Vs. Soda Lime Color Difference?"
the larger one has a more bluish tint to the glass and the smaller one is clearer and more green. On Wikipedia it's saying that the more bluish one is made of soda lime, but how can that be since it was made before 1998 and says PYREX?How can you tell the difference between soda-lime glass and borosilicate?
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.When did Pyrex change to soda-lime glass?
In 1998, Corning sold the Pyrex brand to World Kitchen LLC, which stopped using borosilicate glass and started using soda-lime glass, according to Consumer Reports. Soda-lime glass is just ordinary glass. It's not resistant to thermal-shock, and it could shatter when going from one temperature extreme to another.How can you tell if a Pyrex measuring cup is vintage?
A few well-known details are fairly common to find online: D-handle measuring cups (below, left) are older, open-handle measuring cups (below, right) are newer.How is Pyrex different from soda-lime glass?
Soda Lime glass is sometimes used for glassware which is not likely to be directly and strongly heated, for example petri dishes or TLC chromatography tanks. Borosilicate glass or Pyrex is usually used for glassware that may be directly heated, such as beakers or boiling flasks.Borosilicate Pyrex vs Sodalime Pyrex
More answers regarding vintage Pyrex Measuring Cup Borosilicate Vs. Soda Lime Color Difference?
Answer 2
I think the big question is what is considered vintage? I recently purchased several "vintage" Pyrex measuring cups that have no metric markings. I was thinking they must be fairly old. Marked on the cups, however, they say microwave safe. Microwaves were commonplace in the 1970s. Not so vintage in my book.
Answer 3
As a chemist I don't think that the difference between the two glass compositions would make any difference to you as a cook.
The question is my mind is "vintage." It used to be that the handle on a measuring cup was connected at both ends. How the liquid heats in a microwave causes stresses on the glass. If you put a measuring cup where both sides of the handle are connected in a microwave then it is much more likely to break since a microwave doesn't heat the liquid evenly.
Sources: Stack Exchange - This article follows the attribution requirements of Stack Exchange and is licensed under CC BY-SA 3.0.
Images: Pixabay, Min An, Craig Adderley, Klaus Nielsen