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Volume 2 / Issue 4
Yellow-green, fluorescent, and slightly radioactive, vaseline glass enjoyed great popularity in the latter part of the 19th century up until WWII. The reason for its abrupt disappearance from the consumer market is historically understandable: vaseline glass’s unique color comes from small amounts of uranium oxide. The term “vaseline glass” originates from its distinctive yellow-green hue, which is similar in appearance to greasy Vaseline jelly. Like many uranium-containing minerals, it also glows a bright green color when exposed to longwave ultraviolet light. The accompanying photograph shows a small collection of vaseline glass illuminated by UV light.

Like the uranium in vaseline glass, small amounts of metallic compounds are also responsible for the colors of more common types of glass. Amber bottle glass relies on iron and sulfur for its distinctive hue, while the various shades of green come from chromium oxide. Brilliant blue wine bottles are colored by cobalt.
The SEM micrograph above shows a small chip of vaseline glass slag in back-scattered electron mode. Because heavier elements reflect more electrons than lighter elements, a cord of uranium-rich glass shows up as a bright streak in the image. The EDX spectrum of the cord confirms the presence of uranium (red arrow), among other glass forming elements.

Although a uranium-containing candy dish might sound like a health hazard, incorporating heavy metals into glass is safe due to the relative inert nature of glass and its stable structure. Large heavy metal ions have virtually no mobility inside a silica glass network, which locks them tightly in place. In fact, high-level nuclear waste is made into special glasses before being buried in a process called vitrification. These glasses are designed to trap radioactive material for thousands of years until it can decay into less harmful isotopes. Luckily for consumers, the stability of glass also means that the chromium in millions of green bottles will not be leaching into their beer any time soon.
Although AGR hasn’t yet found uranium in our customers’ glass, we have applied a variety of analytical techniques to determine fracture causes, contamination sources, and cosmetic defects in products ranging from lamp globes to champagne bottles. Contact us if you need assistance with your glass problem.
We know glass – even the weird kinds.


AGR White Paper published in Glass Worldwide

“Filling Line Impact Measurement” is the topic of the AGR Technical Paper just published in Glass Worldwide Magazine the Nov/Dec issue. The paper authored by Senior Scientists William Slusser and Steven Spence discusses measurement of filling line impacts and the relationship to impact testing. To read it visit our Library - White Paper section of our website.

AGR Gets very favorable reviews at Glass Problems Conference

Senior Scientist Peter de Haan received very strong reviews for conducting his short course entitled “Breakage Analysis of Glass Containers” at the 76th Conference on Glass Problems held recently in Columbus, Ohio.  Most notable, reviewers said the following:
  • When asked about the Ability of the instructor to communicate course material, 100% gave an excellent rating
  • Rating the quality of the course, 76% said excellent and the remaining rated it Good.
  • 88% said “excellent” when rating the  “knowledge of the instructor” and the remaining all said “good”
  • The only  negative was a comment that the “class was too short”,  yet one attendee  stated they were “impressed how much was covered well in a 5 hour period”
If you were unable to attend the Glass Problems Conference but would like to attend an AGR Training Seminar, we have lots of opportunities for you. Seminars in 2016 are planned for Bangkok, Thailand, Munich, Germany, Krakow, Poland and Butler, PA, USA. Visit our website to learn more about our full range of Training Seminars or contact us to schedule Private Training at your facility.

Fracture Diagnosis:

Proper interpretation of fracture surface markings eliminates guesswork and avoids the implementation of the wrong corrective actions all of which can save time and money.
The Goal of fracture diagnosis is to locate and identify the fracture origin. Proper interpretation of fracture surface markings:  
  • Indicates the direction of travel and the leading edge of crack propagation
  • Confirms the exact location of the fracture origin
  • Indicates the magnitude and types of stresses present
There are several types of surface Markings:
  • Ripple Marks
  • Striations
  • Dwell Marks
  • Fine and Course Hackle
Knowing which fracture surface markings are useful and properly recognizing them is the key to diagnosing  the cause of the problem.  If you would like to learn more, sign up for one of our “Testing and Fracture Diagnosis of Glass Bottles” Training Seminars held around the globe. Visit our Seminar Catalogue to learn more.

Q: What is the optimal knurl design?

A: Occasionally we are presented with a question regarding the optimal knurl design for a specific glass container design. While it is possible to optimize a container design to improve its resistance to expected loads in a filling line and/or in a trade situation, determining an optimal knurl design is a more complex endeavor.

In a study performed at American Glass Research four different knurl designs were modeled and evaluated through  finite element analysis. The objective of the study was to evaluate  the effect of the knurl shape on the stresses generated on the bearing surface for internal pressure loading.  The knurl types investigated were the radial bar, slanted bar, crescent, and spherical knurls.
The results of the finite element analysis for the four knurl designs are represented graphically in the following pictures:
Looking at the graphical results  it is instantly apparent that the determination of an optimal knurl design is not a straightforward matter. The blue color indicates regions of lower levels of stress, darker blue being a  more significant level of stress relief. Tensile stress concentrations are indicated by the red color, darker being a higher tensile stress concentration. While the levels of stress relief vary at the tips of the knurls, there is also a tensile stress concentration visible at the base of the knurls. The dilemma that presents itself is that handling damage will not be solely confined to the knurl tips and might also find its way into the valley between the knurls. While in this study the highest degree of stress relief at the tips of the knurls  was found with the crescent and spherical knurls, both knurl designs also exhibited the highest tensile stress concentration in the knurl valleys.

The optimal knurl design is often a trade-off between the level of offered stress relief at the tips of the knurls and the magnitude of the tensile stress in the knurl valleys. The key in designing the optimal knurling is to ensure that the tensile stresses in the knurl valley do not exceed the expected surface strengths for those locations.

American Glass Research can assist in determining the most optimal knurl design for any given container design and application.

To learn more about our Design Study Capabilities or to Contact our design team click here.
Using heavy metals for their vibrant colors has a long history in consumer products, sometimes with disastrous results. Perhaps the most famous example is lead oxide in white paints. Another well-known example is a particular vibrant hue of red glaze used for dinnerware serving sets produced until the 1960s. The glaze, sometimes called “Fiesta Red,” also relied on uranium dioxide for its color. Although the radioactivity was orders of magnitude higher than in vaseline glass (see feature story above), the health risk was still negligible as long as the glaze was outside the human body. Unfortunately, the glaze could wear off with usage, resulting in the leaching of the radioactive element into food and beverages.
As for vaseline glass, don’t expect to see vibrant yellow-green bottles gracing the shelves of a grocery store near you. Modern production is limited to a few art glass manufacturers, who focus on decorative objects. The vaseline glass in circulation is largely relegated to antique stores where it commands respectably high prices. If you decide to go searching for some, take a small black light with you. Otherwise, you might be fooled by more common yellow glass – colored with cadmium – rather than the uranium variety.
AGR Training Seminar participation worldwide was exceptionally high in 2015. While new seminars were added to the schedule to meet the demand, several of our more popular seminars filled early and left some potential participants disappointed.  Our  “Fracture Diagnosis” seminars reached capacity both in the US and Germany closing out participation to many would be attendees.  The highly regarded  “Evaluation and Lightweighting of Glass Container  Designs” also filled to capacity in Krakow, Poland.  A new “Audit of Glass Plant Operations” was added to the schedule and many private seminars were held on-site around the world.  To see the full 2016 Training Schedule or to schedule private training at your location, contact us.
American Glass Research
603 Evans City Road, Butler, PA 16001
Tel: +1 (724) 482-2163
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