Uranium glass is a fascinating topic for glass collectors, often drawing them in with its unique characteristics and becoming a must-have. This type of glass reacts to ultraviolet light, displaying a distinctive 'glow' under UV exposure. Its history dates back many years, but it saw a significant rise in popularity during the depression era. Glass items from this period containing uranium are often called Vaseline glass, encompassing a range of items like bowls, cups, and plates, primarily functional rather than artistic.
To understand uranium glass better, let's first explore what uranium is. In simple terms, uranium is a radioactive isotope, meaning it emits radiation. Radioactivity involves the release of energy due to atomic breakdown, and this energy release can be hazardous. It's important to note that there are three types of radioactive emissions: alpha, beta, and gamma rays. Understanding these is key to assessing the safety level of radioactive elements. While alpha and beta rays can't penetrate skin and are only harmful if ingested, gamma rays are more concerning as they can penetrate skin and alter DNA. Gamma rays are particularly formidable because they can travel long distances, off memory around 800-900 km, and are not easily stopped, even by materials like lead. As gamma rays pass through lead, they come out the other side as X-rays which is also harmful in high doses.
Now, why this detailed explanation on radioactivity? It's because I want to share my personal journey with uranium glass. Having a strong science background, with several certifications in radioactivity and radiation safety as well as experience in a laboratory, I was initially wary of collecting uranium glass due to its radioactive nature. Despite assurances about the safety of depleted uranium oxide, I maintained my skepticism. Depleted doesn't mean non-radioactive; it merely indicates a lower concentration of the radioactive isotope. Therefore, depleted uranium is not necessarily safe.
My skepticism persisted until I acquired a Fenton uranium glass boot from the 1940s. Despite being captivated by its glow, I remained cautious and decided to conduct a thorough test using a Geiger counter, a device for measuring radiation. The Geiger counters used in these studies are calibrated regularly and maintained by professionals, as I work in an environment where this is very important. I would also like to add that this equipment doesn't differentiate between ray types. Normal background radiation usually measures up to 30 counts per minute (cpm), with slight variations. My investigation into the uranium glass piece was grounded in my extensive laboratory experience, ensuring accurate and reliable results.
Study 1 – Analysis of a 1940s Uranium Fenton Boot
In this study, a team of professionals, including myself, set out to assess the radioactivity of a Fenton uranium glass boot from the 1940s using a Geiger counter. Initially, the Geiger counter recorded a background radiation level of 32 counts per minute (cpm). As we moved closer to the Fenton piece, the readings increased significantly. At approximately 16 inches away, the counter showed 110 cpm, and at about 12 inches, it registered 132 cpm. Nearing 5-6 inches from the glass, the reading spiked to 268 cpm. The most alarming reading came when the Geiger counter was placed directly above the glass piece, showing a staggering 2766 cpm.
This substantial increase in radiation levels indicated that the glass piece was undoubtedly emitting radiation. To determine the proportion of gamma rays, we conducted further tests. We know that uranium emits a small amount of gamma radiation. By shielding the glass with plexiglass, to filter alpha and beta rays, and positioning the Geiger counter about 5-6 inches from the opposite end of the plexiglass, we discerned that out of the 236 cpm (factoring out the background radiation), 28 cpm was attributable to gamma rays. This finding was concerning, as any level of gamma radiation is unsafe and should be avoided.
Given these results, I immediately decided to remove the uranium glass piece from my collection. This experience intensified my concerns regarding the safety of collecting uranium glass, especially those pieces dating back to the 1940s.
Conclusion: The study reveals that certain uranium glass pieces from the 1940s exhibit dangerously high levels of radioactivity, posing a significant health risk.
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Study 2 – Analysis of EDAG Uranium Glass from the 1960-1970s
Over time, I accumulated several pieces of EDAG, Canadian vintage art glass with uranium content. These pieces were aesthetically pleasing, and I was keen on retaining them in my collection. However, given my previous findings about uranium glass, I was compelled to conduct a thorough scientific assessment before making any decisions. My hypothesis was that not all uranium glass is created equal, and with the advancement of years and stricter radiation regulations, these later pieces might exhibit different characteristics.
Under similar conditions and using comparable equipment to the previous study, I embarked on study number 2. I selected a variety of EDAG pieces for testing: a plum-over-green uranium ashtray, a blue-over-green uranium gondola, and a plum-over-green uranium basket. The results were surprisingly reassuring. None of the items tested registered radiation levels above the background count of 32 cpm. This was consistent even when the Geiger counter was placed directly above and around the pieces (Geiger images not shown as there was nothing significant to document).
This finding suggests that EDAG uranium glass pieces from this era do not emit excessive radiation into their surroundings, essentially indicating that they are safe for inclusion in an environment. It's crucial to note that this doesn't imply these items emit no radiation; rather, the emission levels are not higher than the typical background radiation we encounter daily.
It's also important to dispel the misconception that all uranium glass will trigger a Geiger counter. This is not always the case. Additionally, many household Geiger counters may not be accurately calibrated (a process that should ideally be done monthly by a professional). Hence, readings from such devices should be approached with caution, understanding that only some uranium glass will activate a Geiger counter.
Conclusion: The study on EDAG uranium glass from the 1960-1970s reveals that these pieces do not emit harmful levels of radiation, making them safe for regular environmental exposure. This finding highlights the variability in uranium glass and underscores the importance of accurate testing and calibration in assessing their safety.
Study 3 – Examination of Victorian Glass from the 1880s
I was given a Victorian bridal basket, an ornate glass piece typical of the Victorian era. The basket, featuring a ruffled rim that included uranium glass, immediately piqued my interest and concern. Given the era in which it was crafted, it was uncertain whether the glass contained the later-known depleted form of uranium oxide. The understanding of radiation was still in its infancy during the 1880s; even Marie Curie, who discovered radium and other radioisotopes around 1910, suffered from radiation poisoning due to her exposure. This historical context set the stage for my apprehension about the safety of this Victorian piece.
Thus, I initiated study 3, focusing on the Victorian bridal basket. The Geiger counter's reaction was immediate and alarming. As the pointer edged towards its limits, the lab was filled with the loud clicking the Geiger emits when faced high radiation levels. The readings oscillated between 425-500 counts per minute (cpm). After subtracting the 32 cpm background radiation, the resulting radiation level was extraordinarily high. The severity of these readings rendered any additional testing, such as using plexiglass shielding, unnecessary.
The conclusion was clear and decisive: this Victorian glass piece, while historically and aesthetically significant, was emitting dangerous levels of radiation. I decided unequivocally against keeping this potentially carcinogenic item in my environment. The study underscored the variability in safety and radioactivity of uranium glass across different eras, with this particular Victorian piece posing a significant health risk.
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How to Identify Uranium Glass
As we wrap up this blog on uranium glass, I'd like to offer some guidance on accurately identifying this unique type of glass. There's often confusion and misinformation surrounding its identification, sometimes exacerbated by altered photographs in sales listings. It's essential to recognize that various minerals, chemicals, and metals can cause UV-reactivity in glass, not just uranium oxide.
A frequent mistake involves confusing manganese with uranium. Manganese, a metal used to create purple hues in glass, is often employed to neutralize green tints and achieve a crystal-clear appearance. This means manganese can be present in a variety of glass pieces, especially in leaded glass where it offsets the lead's color. Under UV light, manganese exhibits a mild green glow. This subtle glow often leads to the incorrect identification of glass as containing uranium, particularly when photographs are enhanced to exaggerate the effect. Remember, uranium glass glows intensely, deeply, and uniformly. Any muted glow or stronger fluorescence along lines or creases suggests the presence of manganese, not uranium.
There are other UV-reactive components used in glass-making, but their glow is distinct from the green or yellow typically associated with uranium. To illustrate the difference, let's compare the glows under UV light at wavelengths of 365nm and 395nm. A 365nm UV flashlight is generally preferred due to its minimal violet light emission, which enhances fluorescence. However, this very property can lead to confusion, making manganese appear more like uranium due to the stronger fluorescence. Keep this in mind when using a 365nm light source for identification purposes.
UV light 365nm wavelength
Chalet Glass egg showing Manganese vs Uranium in an EDAG piece
UV light 395nm wavelength
Chalet Glass egg showing Manganese vs Uranium in an EDAG piece
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