The "pyrex", made of soda lime glass, by World Kitchens is not made in China. It is made in the US at the old Corning Charlerois, PA. Pyrex plant which they bought. It is all usually still marked in some form "USA" so this is not reliable. WK actually claims that Pyrex was made of soda lime glass since the 40s and it is true that some was made of soda lime glass. It was all the opaque, mostly white type and all made at the Charlerois plant. The clear colorless, borosilicate Pyrex was made in other plants. Evidently the plants are specific to the type of glass. The problem with the soda lime is that it will only tolerate about a 100F difference of temperature within the piece of glass. Borosilicate tolerates about 300F. Pyroceram, the old Corningware tolerates 8-900F difference within the piece. Corningware was also bought from Corning by World Kitchens and now is stoneware, made in China. They did in 2009 start manufacturing pyroceram again, in France but it is prohibitively expensive. It is easy to find the real stuff on the secondary market and often in pristine condition. There is also another Corningware, SimplyLite, vitrelle glass made in Corning NY but it may have been DC'd There are some ways to tell the difference between the old and new Pyrex, but all you can do is reduce the risk of shattering not elininate it. I would not use anything in the oven or with heat.- --marked "pyrex". lowercase--This is the newer trademark and if you look at the http://www.pyrex.com/ website, the borosilicate glass is still trademarked "PYREX" and the soda lime is "pyrex". Clear colorless "PYREX" is most likely borosilicate. Some of the newer "pyrex" dishes have really big handles which cool more rapidly and increase the chance the dish will shatter. --anything opaque. These are vintage and marked marked "PYREX" too and mostly are white. They are soda lime glass --anything needle cut-I have a cute little pie pan but the needle cutting damages the integrity of the glass This would be on a vintage PYREX piece. --anything with visible damage, nicks or cuts Glass can bruise and shatter without warning. --avoid thicker pieces, with bluish or green coloring This is a little more subtle and there is a bluish clear early "PYREX" marked flameware that can be used on gas or electric elements with a trivet. http://en.wikipedia.org/wiki/Pyrex#mediaviewer/File:Pyrex_and_PYREX.jpg I decided to replace my PYREX with pyroceram where I could. There is Corningware,Arcoflam, Narumi, Pyrosil, Pyroflam and the old Visions line made of Calexium. The pyroceram is smooth on the bottom. The stoneware is thicker and has a bump round the edge. The stoneware says no stovetop or broiler. http://cookinwluv.blogspot.com/2011/07/blue-cornflower-corningware.html I don't like pyroceram on the stovetop because it doesn't cook evenly but it is great for bakeware. The only problem is you can't see through it. Corning tried to address the poor heat conduction by making the "Rangetopper" line that has metal on the bottom. I think this is to avoid the exposure of the heat from the element coming on for preheat.
