Get out your Geiger counter! Certain 19th century green glass can zing with radioactivity…. but the luscious green colours produced will have you in awe. Line up a few pieces of antique “uranium glass” on a window sill, and “when the sun is over the yardarm” you will have a sure visual cure for the blues of winter. (Banner photo courtesy of Dave Peterson at

This 19th century condiment server is a pale green in regular light…

….but a UV light or the sun’s natural UV rays will make the green glow in  fluorescence. (Image via

Uranium glass (or ouraline as it is termed in French), is glass which has had uranium added for coloration. The proportion ranges from minuscule levels to about 2% (although some 20th century pieces were made with up to 25% uranium).

19th c. Bohemian dog buttons in uranium glass.( images via

It is the uranium which makes this 19th c. glass box glow, not the reactivity!  Sold for 450 euros at auction.

One might deduce that uranium glass glows green because of  reactivity, but this is not the case. “It is the chemistry of uranium that makes the glass glow, not radioactivity”, explains expert Barry Skelcher (whose collection once numbered over a thousand pieces).  Uranium glass glows green under ultraviolet light. Under normal lighting, uranium glass objects can range from pale yellow to medium green, varying from opaque to transparent.

Uranium glass keg and mugs produced in Ohio by the Cambridge Glass Co. in the beginning of the 20th c. (Photo via Dave Peterson at

A bit of history…

Even before the discovery of uranium as an element, uranium compounds were used for centuries as a coulourant for glass. We can date uranium glass back to at least 79 AD in the form of a mosaic fixed in a small niche in a wall of the Imperial Villa on Posilipo near Naples. This mosaic combined yellow glass with 1% uranium oxide.

Somewhere in this wall decoration of the Imperial Villa in Posilipo, one finds uranium glass mosaics dating from 79 AD.

In the late Middle Ages, pitchblende (or uraninite) was extracted from the Habsburg mines in Bohemia (now part of the Czech Republic) to be used as a colouring agent in the local glassworks. German chemist Martin Klaroth discovered the uranium element in 1789 and further studied its use as a colourant for glass. Originally, uranium was seen as nothing more than just another mineral to colour clear silicon dioxide, the main constituent of glass. Scientists already knew that cadmium turned glass yellow, cobalt produced a blue, manganese brought out violet hues and certain compounds of “gold” turned red when heated, blown and cooled.

This Bohemian cup and saucer were produced for the Persian market around 1850.  (Photo via Dave Peterson at

If there is a signature red crystal, it’s Baccarat.

Even today, red glass in general is often considered the most coveted and expensive, no doubt due to this association with gold. Baccarat goes so far as to emphasize the fact by identifying each of their contemporary chandeliers with one “red” signature crystal.

Baccarat oval molded glass plate sold at auction for 278 euros.

The extraction process for uranium salts was greatly refined in the 1840s leading to a surge in green uranium glass. Between 1880 and the 1920s, uranium glass became the rage. The Austrian Franz Riedel was the first major producer, but soon other European glassworks developed new varieties. For instance, Baccarat developed a green uranium glass which they named chrysoprase from its similarity to that green form of chalcedony.

Baccarat green chrysoprase  vase. (image via

Uranium glass was made into tableware and household items (some quite curious), but fell out of widespread use when the availability of uranium for civilian purposes was sharply curtailed in the 1940s.

According to UK Antique Roadshow’s glass expert Andy McConnell, at the beginning of the 20th century, uranium glass objects were often given as wedding gifts amongst the working classes. In this context, a piece of uranium glass might be the one thing of visual extravagance  in an otherwise drab household setting.

In the States, commercial manufacturing of uranium glass has ceased although small glass makers still continue to make pieces whenever vaseline cullet can be found. This is because of tighter government regulations regarding uranium dioxide, the ingredient in the batch that makes glass glow. Contemporary uranium glass is now mainly limited to small objects like beads or marbles. Small shops in Europe continue to produce some vaseline glass, but is still somewhat limited. The Riihimaki Glassworks in Finland, however, continues to produce uranium glass in designer art pieces.

Riihimaki Lasi Yellow Paukkurauta Vase/Bottle
artist:  Erkkitapio Siiroinen

Anyone for iso-typing? Steve Klein’s steam punk keyboard is one of the more unusual objects one finds in uranium glass.(Images via )

19th c. uranium glass household objects like this juice squeezer are popular finds in flea markets. (Images via Thomas A Durston)

About the only form of uranium glass still made today is found in marbles. (Images via

Thus far, I have purposely avoided bringing up the subject of “vaseline glass”. By the end of the 19th century, glassmakers discovered that certain mineral additions to uranium glass, when tempered at high temperatures, lead to increasingly opaque varieties of colour –traditional transparent yellow or yellow-green to an opaque white. In the United States and Australia, this new glass got the nickname “vaseline glass” because of its similar appearance to petroleum jelly. Confusion reigns in the terminology of “vaseline glass” and it often is used mistakenly as a catchall definition for any pressed, pattern, or blown glass with a urinous colour. In the UK, the terminology for uranium or vaseline glass is Primrose Pearline, Davidson, Greener and Sowerby.

The candlestick on the left is “vaseline” glass, while the glass mug in the center has been colored with iron and if it glows, would be considered “uranium” glass. (Image via

Vaseline glass is not harmful but does emit a very small amount of radioactivity.  Both vaseline glass and uranium glass will glow a neon green when exposed to UV light but for collectors in the US, vaseline glass is yellow to yellow green.

Today, the production of vaseline glass by major glass companies like Fenton Glass and Mosser Glass has ended but individuals like jack Loranger still produce a limited amount of pieces when vaseline cullet can be found.

Uranium glass is affordable. At auction, a mere 10 euros for this 19th c. Moser vase.

The popularity of uranium glass began to wane long before concerns were raised over the potential harm of radioactive materials. What makes uranium glass so unique is that it fluoresces under ultraviolet (UV) light. Even without black lights or UV lamps, uranium glass gives off a slight green glow in ordinary daylight, courtesy of the sun’s natural UV rays. At dusk, the effect of ultraviolet light is more marked and glass coloured with uranium will appear to glow. One collector divulges his methodology for picking out uranium glass quickly. At an outdoor antique show, he waits until the sun begins to go down, he can then look about and easily pick out the glowing objects in the various stands.

At dusk, the uranium glass objects at a flea market stand begin to glow. (Photo via Dave Peterson at

While the 19th century was fascinated by the glow of uranium glass, the electric light became more widespread in homes in the 20th century.  The fascination for the evening glow of uranium glass was lost to the light bulb, a fact which contributed to uranium glass’ fall from fashion.

This silver and uranium glass perfume bottle was recently sold at auction for a mere  30 euros.

Novelty items like this wheelbarrow, produced by Adams & Co. in Pittsburgh, were used to hold matches or salt. (Photo via Dave Peterson at

Highly collectable and fun…

Uranium glass is easy to collect. On both sides of the Atlantic, one finds 19th century examples in the form of butter dishes, plates, biscuit jars, vases, door stops and decorative objects.  Flea markets and garage sales abound with uranium glass finds at affordable prices. An important set of hand blown ouraline glassware by Émile Gallé (the French artist considered to be one of the major forces in the French Art Nouveau movement) fetched 1.100 euros at auction February 11th at the Hotel Drouot  Paris.

While there are a number of associations for uranium/vaseline glass oficianados internationally, one of the most dedicated groups is Vaseline Glass  Collectors, Inc. Association Treasurer, Tom Foozer, a collector and enthusiast describes the group’s founding in July, 1998:

“… fifty or so vaseline glass enthusiasts from around the United States met at the Kansas City, MO airport, bringing with them treasures they had collected over the years.  Table were aligned around the room to display these treasures and that’s when the magic happened.  The diversity of manufacturer’s glass, the vivid colors of red, blue and pink blended with the glow of the vaseline glass and was quite a sight to behold!  Never before has any of us seen so much vaseline glass in one place!

Speaking to one another about the glass allowed us to learn where it came from, who the manufacturer might be and best of all, the chance to see pieces that many of us did not know existed.  The commonality we shared in our love from this glass and our willingness to share what we know became the fundamental charter for our club.  That desire to share and educate still exist today.”

Tom says that Vaseline Glass Collectors, Inc. (VGCI) meets once per year, typically in October to carry on what was started 20 years ago and that over the years club members have developed friendships that will last a life time. If you have a question, don’t hesitate to contact them on their website or via their facebook page  With over 3,400 followers, any questions you may have are welcomed and they are always interested in seeing what treasures you may have discovered!

This rare example of a uranium absinthe glass fetched 1.500 euros.

Another enthusiastic group of collectors (especially in Europe) are the “Artemisophiles” (people who collect antique objects linked to absinthe) – no doubt it is the colour which attracts them.  One of the most expensive examples of uranium glass to come up for auction combined two edgy subjects – absinthe and uranium glass – in the form of a drinking glass with a liquor dosing feature incorporated in the stem.

You can’t get quirkier than this uranium glass bulldog door stop.(images via: Globe Antiques & Collectibles)

The English firm of George Davisdon & Co. produced this Somerset pattern in 1895.  (Photo via Dave Peterson at

Is uranium glass dangerous?

The glass emits radiation, but the amount is infinitesimally small. Granted it is “uranium” we are talking about… but our bodies are subjected to higher levels every day from household objects like smoke alarms and foods like bananas, spinach and baked potatoes. (The only way to get enough uranium into your system to do you harm would be to grind up a piece of uranium glass and swallow it.) It should be noted, however, that the Environmental Protection Agency in the US has cautioned against using uranium ware to hold foods or drink. (Not to digress, but this warning also applies to orange-red Fiestaware currently all the rage for lovers of 1950s and 60s design.) Perhaps it is best to consider your uranium glass as art objects rather than utilitarian vessels.

Hold the milk…It’s probably prudent to listen to the EPA and turn these 1880s alphabet mugs into decorative objects. (Photo via Dave Peterson at

Is the “sun over the yardarm” on the subject?

In closing (and slightly off the beaten subject) but in the interest of crossing all the t’s and dotting the i’s, I began this post employing the adage “when the sun is over the yardarm” referring to the time of day when uranium glass should do its magical thing. As you probably know, this is a traditional nautical expression indicating the time when it is acceptable to have the first alcoholic beverage of the day. (I always assumed this might be around 18 hours – coinciding with high tea perhaps?)

The sun is over the yardarm somewhere….

But no… the course of researching this post, I discovered that in the north Atlantic, where the phrase seems to have originated, the sun would show above the foreyard of a ship at about 11 o’clock in the morning. (Many ships would then do a “stand-easy” and officers could slip below deck for their first rum of the day.) This is a tad early even by my standards.

Inexplicably, I have been waiting years for an essay opportunity to use the yardarm expression.  So rather than rephrase my first paragraph, let me leave it “as is” and add a point of precision on the subject of the yardarm and uranium glass.

If you begin studying your uranium glass “when the sun is over the yardarm” (i.e. before lunch), the only way you will see the magic is if you lighten up somewhat on the uranium and go very, very heavy with the rum. Granted, there is no telling who or what will glow after that!

One needs to be patient and wait till the sun goes down to admire the magic of uranium glass. “Game of Thrones” author George R. R. Martin once observed, “When the sun has set, no candle can replace it.” That might be true, George, but uranium glass was certainly the 19th century’s means of trying.

The sun is definitely over and under the yardarm for this 19th century uranium glass skull! (images via:

Very special thanks to VGCI’s glass enthusiasts Tom Foozer (text) and Dave Peterson (photos) for their invaluable assistance with this post.

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