Pyrex. What does that mean to you? Many of us think of mom, or grandma, and all the bowls and casseroles that they prepared for us.

Pyrex is a brand of milk glass, which has many other names depending on what the product is being used for. There are similar brands like Fire King, Federal, Indiana, Westmoreland, and others. Most are marked or stamped on the bottom with the company name.

Pyrex was introduced by Corning Inc. in 1915 for a line of clear, low-thermalexpansion borosilicate glass used for laboratory glassware and kitchenware. The origins of Pyrex lay in a problem the early-20th century railroad industry faced with broken lantern globes. When hot, contact by rain or snow would cause them to crack. Corning Glass was engaged to come up with a solution, which they did in the form of a glass formula they dubbed Nonex. While the perfect answer to the railroads’ breakage issue, it was ultimately unprofitable in that few of the new type globes required replacement thereafter.

The railroads got a great product and the company found a new avenue to sell the glass. Corning researcher Jesse Littleton brought home a borosilicate pan for his wife to try. In her experiments with it, she found that the foods cooked faster, at lower temperatures, with the added benefit that she could see the food as it cooked. With the new formula altered to remove lead, work proceeded to develop a cookware line from it, which the company called Pyrex.

Milk glass is an opaque or translucent, milk white or colored glass that can be blown or pressed into a wide variety of shapes. It was first made in Venice in the 16th century. American milk glass is a popular collector’s item that primarily dates back to the turn of the 19th century up through the 1950s. This delicate glassware was used to make items such as bowls, mugs, candleholders, and more.

I bet if you are reading this, you have some milk glass. Use it. Enjoy it. Do not put it in the dishwasher if it has any decor or color. Do not put it in a microwave if it has metallic paint. It can go from the freezer into the oven. I prefer to put it in while the preheat is starting, but you don’t have to. This glass should not shatter; it can go from cold to hot quickly.

My favorite pieces are the originals from the 1920s. I use my hundred-yearold pieces every day. Pyrex patterns can be rare and hard to find. The collector market is booming, but not everything you have has collector value.

As always, if you are curious about what you have, send me a picture and your questions at pamspantiques@gmail.com.