
Logan of Doesn'T Matter, IL on Oct. 20, 2009
Just ran across your article about exploding Pyrex. After reading the subsequent response from World Kitchen's lawyers, I felt that I needed to offer a rebuttal to some of their claims, since as a scientist I can tell you that the lawyers are seriously spinning the facts and misdirecting attention so as to avoid the blame that their company rightly deserves.
First off, I AM somewhat of a glass expert. Probably not as good as the experts you consulted from your original article, but I do hold a MS degree in Glass Science, and am currently doing materials research into glass-ceramic materials. With that said, some things you might want to consider. For ease in correlating arguments, I'll refer to the statements put out by World Kitchen's lawyers using their numbering system.
1. "Contrary to what Consumer Affairs Says, World Kitchen Did Not Change the Formulation of Pyrex Glass Bakeware; the Formulation is the Same as that used by Corning."
Response: Granted, I do not personally know when the formulation for pyrex glass was changed from borosilicate (BS) glass to soda-lime-silicate (SLS) glass. I don't work for Corning and don't have access to those records. What I DO know for certain is that after World Kitchen purchased Corning's kitchenware division they DID SIGNIFICANTLY change the formulation of the bakeware under the CorningWare brand label. That change was from a very strong (and extremely thermal-shock resistant) glass-ceramic material to a much weaker (and cheaper) stoneware ceramic. Although the materials changed, the dish appearances and names did not change. Thus, we have a very concrete example of World Kitchens deliberately changing product compositions for financial gain while depending on consumer expectations of the previously superior product to continue driving sales. If we cannot trust this company with the way they adulterated the CorningWare product line, why should we believe that they are telling the truth about Pyrex?
There is a simple way to test their claims. Just purchase several "antique" pyrex dishes from estate/garage/auction sales and send those off to a trusted facility to test their composition and construction. Based on the product stamps and/or packaging you can confirm if they were manufactured prior to 1998. If an independent lab can confirm that an old "beat up" dish still possesses superior composition and tempering than the new products, then your original calims will still stand, despite the lawyers' bluff.
2. "Contrary to what Consumer Affairs Says, Pyrex Glass Bakeware is Properly Tempered."
Response: In point number two, World Kitchen's lawyers posit that the tempered SLS glass is of equal (or superior) quality to that of BS glass. Despite their insistence, the scientific fact still remains that SLS glass -- tempered or not -- will ALWAYS have a thermal coefficient of expansion (COE) which is much greater than that of borosilicate glass. The COE for a glass is a physical property of the material and is a function of glass composition only. It is this thermal expansion that is ultimately responsible for causing bakeware to break in the oven when the Pyrex tempering fails to constrain the thermally-induced stress. Thus, as you and your glass experts initially stated, SLS glass articles are inherently inferior. What you'll notice in the lawyers' carefully worded response is that they claim the tempered glass is "comparably resistant to breakage," not comparably resistant to thermally-induced stress. However, it is only "comparably resistant" because the tempering process adds enough strength to cover the inherent flaw caused by the difference in glass composition. Borosilicate glass does not require the same tempering because the material itself is inherently superior. A tempered borosilicate article would then be vastly superior in not only thermal shock resistance but also mechanical resistance, leaving no advantage at all to the SLS dish.
3. "Consumer Affairs Ignores the Scientific Fact that Pyrex Glass Bakeware is Tempered Differently than Flat Glass."
Response: "Tempered Differently" is NO excuse for TEMPERED POORLY. As a glass expert, I'll agree with World Kitchens than it is very difficult (and probably not worth the time and effort) to temper every square inch of a bakeware dish as evenly as a flat panel of glass. Also, I'll concede that Pyrex bakeware would not be expected to dice when it breaks. I've intentionally broken several antique Pyrex dishes in the course of my research, and they do indeed break into large shards instead of small crumbles. However, knowing how the tempering process works, it would reasonably be expected that two-dimensional regions of similar thickness within an article (such as the centers of the dish bottoms) would exhibit the same degree of tempering, and that the tempering from multiple pieces would be equal. As your experts noted and the lawyers conveniently ignored, the issue is not a question of whether it is tempered the same as plate glass, but whether it is tempered sufficiently to protect the consumer, and the answer that we've seen from the consumer experience is a resounding No. The question thus remains unanswered, how does the quality of tempering in today's dishes compare with those from before World Kitchens took over?
4. "Contrary to what Consumer Affairs Says, Pyrex Glass Bakeware is Durable and Impact Breakage is an Important Safety Consideration."
For the most part, this response from World Kitchens is valid. But, again the validity of their response hinges on the assumption that the articles have been manufactured with sufficient tempering to increase their strength. They also cite NEISS statistics to show that thermal shock accidents are far fewer than incidents caused by dropping. What we do not know from their response, and what should be investigated further, is how the relative incident rate for breakage by dropping has changed pre/post-world Kitchen era, since a decrease in production quality should see an increase in incidents. Also completely ignored by the lawyers is the point of consumer expectations that is, consumers expect a dropped glass dish to break, while they do not expect a stationary one to shatter. In this case, even one to three incidents per year of spontaneous shattering is still too many when those could have been prevented.
5. "Consumer Affairs Misrepresents the Differences between Soda Lime and Borosilicate Glass Manufacturing, and Ignores the Damaging Environmental Implications of Borosilicate Glass Manufacturing."
Response: As a glass scientist, this argument from World Kitchens was the greatest affront, and practically had me laughing in disbelief at their attempt to redirect the argument. Dr Day's statements are solid fact, which is why the lawyers then proceed to set up several straw-man arguments around this point so that we'll try to ignore those facts. As I mentioned earlier, there is a great difference between comparing MATERIALS and comparing PRODUCTS. From a materials perspective, borosilicate glass is immensely superior to soda lime glass. That's why Corning Inc. still retains the right to make BOROSILICATE glassware for laboratory use under the Pyrex label. World Kitchen's "Pyrex" glass is only remotely similar due to their additional processing steps to add strength, and again, if they fail in that secondary process (as they apparently have) it is the consumer that suffers harm. Contrary to the lawyers' claim in this paragraph, the melting point of the glass compositions DOES impact the final product. If a manufacturer doesn't sufficiently melt the glass batch materials at a high enough temperature, it can cause stones and other inhomogeneous defects to end up in the final glass article. These defects then create stress points that induce failure in the consumers' kitchens. Finally, the "environmentally friendly" argument is laughable because the energy efficiency of the manufacturing process has nothing to do with safety of the consumer in their home, except when the company's focus on said energy efficiency (and subsequent cost savings) leads to an inferior product.
6. These arguments made by World Kitchens either involve conversations that I was not part of, or are petty personal attacks on the credibility of Consumer Affairs' website, thus I have no comment.
Bottom line: This issue is all about the MATERIALS first, and the production methods second. A material with very low thermal coefficient of expansion will not explode in a consumer's oven under normal use, regardless of the degree or quality of the tempering that it has undergone. Borosilicate glass is inherently safer because it cannot generate the amount of internal stress that soda-lime glass will. If World Kitchens really cared about the consumers and not just their stockholders, they would make their "Pyrex" bakeware out of the same borosilicate glass that Corning uses for their Pyrex labware -- the same material that the public EXPECTS when they buy a product with the Pyrex label.