Just What is "T-Glass?"
If you've been buying and using Spectrum glass for awhile, no doubt you've run across the phrase "T-Glass". Ever wonder what it really is and how it comes about?
Originally, the "T" stood for "transition". We used it to designate glass colors that were produced during the transition from one color to another in our continuous-melt furnaces. For example, if we were producing dark blue and wished to change the color to medium blue, a shade between the two might be made as the glass gradually changed color. There was nothing really wrong with the T-Glass, it was just lighter than one standard shade and darker than another. But in order to maintain the integrity of our standard colors, these "in-betweens" had to be segregated out.
Color is just one characteristic that goes into defining a standard. As our quality control systems evolved so did our tolerances with regard to other glass properties. Each product was soon being judged for surface texture, mix proportion, light transmission and other qualities. When a glass fell outside the tolerance range, it also received a T-Glass classification. So T-Glass came to encompass any glass we make that, for one reason or another, falls outside the QC limitations for it's standard.
Structural tolerances are a different matter altogether. These are glass problems that translate into poor cutability, sheet warp, or structural weakness. Glass is not classified T-Glass for these reasons. In fact, when these problems occur, the glass is not classified at all; it is trashed. So if you buy T-Glass, you can depend on it cutting just as well as any other Spectrum product.
T-Glass is often a fine buy and a good way to save money on glass. The most common problem people encounter is needing to match it in the future. We don't make T-Glass on purpose, of course, so availability is never assured. Plus, T-Glasses with the same stock numbers may be quite different. A glass called T/132W from one run may have an inadequate texture. The same glass from another run may be off in color. Keep these things in mind when you order T-Glass.
We sell T-Glass to Spectrum distributors at a discount from the standard glass price. We encourage them to identify the product as T-Glass when they re-sell it, and most cooperate. Some are guilty, though, of advertising Spectrum glass at reduced prices and then selling T-Glass without letting the buyer know. This hurts us and the buyer too. If you order 132W from a distributor and he supplies you with T/132W, it makes us look bad. So, if you're buying discounted glass, be sure to confirm whether it is standard product or "T".