I have had a number of new collectors ask about the presence of Uranium in depression glass, and, in particular, they wonder if it might be dangerous. So I got to thinking that maybe collectors ought be interested in some of the Ingredients that were commonly used to produce our beloved depression glass. First off, let ne calm, any fears you might have about the uranium. Yes, it was an ingredient used to color yellow and green glass. That is what makes the glass glow under a black light. That is what makes "vaseline glass" have its wonderful color. But it is not at all dangerous. The amount of uranium oxide that was added to a batch of glass was miniscule compared to the amount of other ingredients, and the uranium oxide itself was not a highly radioactive substance (uranium used in the atomic bomb was highly refined to extract a particular type or uranium which is actually quite scarce).
There were other scary-sounding ingredients used in making glass, so let's take a closer look at what went into our favorite collectibles. The principal ingredient in glass is pure white silica sand. It has to be at least 98% pure, or it is unsuitable for glassmaking. The next largest ingredient is soda ash. Most of the glass formulas, regardless of what type or glass you are making, consist of these two Ingredients. Fairly harmless, right? There are two types of glass that were used to make glassware during the depression years: lime-soda glass and lead glass. For the lime-soda glass, you would add lime to the silica sand and soda ash (it figures that you'd add lime to lime glass). For lead glass - surprise - you add lead to the silica sand and soda ash. Lime-soda glass was used to make most of the pressed dinnerware items in depression glass patterns. The lead glass was used to make blown items like stemware and vases. Regardless of which type of glass was being made, arsenic was added to the glass formula. That's right - arsenic. It was specifically used, along with sodium nitrate, to reduce the bubbles that formed as the ingredients were being melted. In fact, if the arsenic and sodium nitrate didn't do a good enough job in reducing the bubbles, workers tossed in two or three potatoes! Yes, potatoes. They would explode in the mixture, releasing lots and lots of bubbles.
If the manufacturer is making colored glass, then there were additional chemicals added to the glass mixture. Some of these include compounds of the following elements:
Where a formula for glass might call for 1,400 pounds of silica sand and 540 pounds of soda ash (these numbers were taken from an actual glass batch formula), the coloring agent for the mix might be something like 4 pounds of uranium oxide. Four pounds of anything mixed in a ton of other stuff is a pretty insignificant amount. The amount of arsenic added to the same formula might amount to about 5 pounds, and all of it is essentially used up in the process of removing the dissolved gas bubbles before the pot of glass is ready to be used. Similarly, small amounts of the coloring agents are used for the various colors. To make lead glass, using the same 1,400 pounds of sand, the company might use up to 6OO pounds of lead compound. That doesn't mean that you have anything to worry about - the lead is part of the glass itself, and the lead compound is what gives the glass its clarity.
As World War II progressed, some of the ingredients used in the making of colored glass became strategic for the war effort. The glass companies discontinued most colored glassware by around 1944, making mostly crystal. After the war ended, the buying Public wanted different colors and treatments -- things that didn't remind them of the hard times they had suffered during the depression years. So the post WW II colors were often quite different from depression glass colors, but the same "toxic" ingredients were still used to produce colored glass, and they are still being used today.