If they set glass out and it turned purple, it proved to them and to their customers that the glass was, indeed, made prior to ca. 1915 when most, but not all, glass companies ceased using manganese and substituted selenium as the clearing agent.
true bright pink, like true bright purple, are ultra rare. Most purple sea glass is actually “sun” purple – in the old days manganese was added to glass as a clarifying agent, and manganese turns purple when exposed to UV rays – like those in sunlight.
From 1885 to 1914, manganese dioxide was used as a clearing agent by glass makers to make sure the glass remained clear. However, when exposed to the sun over time, the manganese dioxide in the glass will cause the glass to turn a purple tint. The main source of this clearing agent was Germany.
Manganese-decolored glass that has undergone a color change due to exposure to the ultraviolet rays of the sun is variously known as sun- colored amethyst (SCA), solarized amethyst, solarized purple, or irradiated glass.
The reason for discontinuation was a combination of economics and a problem in the manufacturing and processing of the blue base glass. The blue glass used in the glass Weld-Cool filter plate was a specialized type of cobalt glass ... not just plain cobalt glass.
If they set glass out and it turned purple, it proved to them and to their customers that the glass was, indeed, made prior to ca. 1915 when most, but not all, glass companies ceased using manganese and substituted selenium as the clearing agent.
Some types of blue glass — also commonly known as cobalt glass — may be more valuable than others due to their rarity, craftsmanship, or historical significance. For example, antique blue glass from a well-known maker like Blenko, Empoli, or Murano, may be more valuable than more unmarked, contemporary blue glass.
Some of the more valuable colors are cherry red, black amethyst, and ice green. Take note of the iridescent quality of the antique glass to be sure there are no worn or uneven sections.
Historically, for African Americans, the purple glass is a symbol of burials in African American cemeteries. You carry a purple vessel with water in it and smash the glass vessel on a tombstone.
Favrile glass. Tiffany patented Favrile glass in 1892. Favrile glass often has a distinctive characteristic that is common in some glass from Classical antiquity: it possesses a superficial iridescence. This iridescence causes the surface to shimmer, but also causes a degree of opacity.
Manganese is one of the oldest glass additives, and purple manganese glass was used since early Egyptian history. Manganese dioxide, which is black, is used to remove the green color from the glass; in a very slow process this is converted to sodium permanganate, a dark purple compound.
From the 1960s onward in the United States, with improvements in shipping and storage materials, glass bottles have almost completely been replaced with either LDPE coated paper cartons or recyclable HDPE plastic containers (such as square milk jugs), depending on the brand.
Red sea glass is widely regarded as the rarest of them all. The scarcity can be traced back to the past when production of red glass was not as high as the other colors. Red glass was typically used in limited quantities for specialty items such as warning lights, lanterns, or decorative glassware.
Tyrian purple: The lost ancient pigment that was more valuable than gold. For millennia, Tyrian purple was the most valuable colour on the planet.
This is significant to seaglass collectors, because it helps date pieces. It was discovered later that glass bottles made with manganesum eventually turn purple from UV-rays that hit the glass. The longer the exposure, the richer the color purple can develop, in addition to the amount of manganese dioxide used.
Is "sun-purpled" glass a good investment? On the contrary, it is tantamount to purchasing a piece of damaged glass and the value is decreased as though it had a serious crack or chip.
In the early 20th century, changes in manufacturing processes, as well as more pure batch materials, dictated different ways to decolorize glass, and the use of manganese oxide for this purpose dwindled.
Purple or as you will hear often, 'Amethyst' glass, was given its color by adding manganese oxide to a molten glass mixture of sand, potash and lime. Purple or Amethyst glass should not be confused with clear antique glass that has changed color due to sun exposure (see picture to left).
Some of the most collectible types & styles of antique and vintage glassware include Depression Glass, Carnival Glass, Milk Glass, Moonstone, Hobnail Glass, and Jadeite. One of the most popular styles of antique glass was a Hen on Nest, also known as Animal Dishes because of the variety of animals they come in.
Color and pattern, which helps identify both the rareness of the piece as well as its manufacturer. Some of the most valuable colors are cherry red, black amethyst, and ice green.
The auction record is £;520,000 ($1,078,480) for a Roman glass cage-cup of c.AD 300, known as the `Constable-Maxwell cage-cup', measuring 17 cm (7 in) in diameter and 10 cm (4 in) in height, sold at Sotheby's, London, UK on 4 June 1979 to Robin Symes (UK) of the British Rail Pension Fund.
If your glass has a blue tint to it, it is likely cobalt blue glass. There are three shades of cobalt glass; dark cobalt, which has a slight purplish hue, light or cornflower blue and medium blue. To verify its authenticity, check with an appraiser.
Cornflower blue sea glass comes from bottles and tableware with limited amounts of cobalt oxide added to the glass mixture. Far fewer cornflower blue items were manufactured, making finding this color about twice as rare… and its paler shade makes it much harder to see.
Although amber glass provides more UV protection for light-sensitive products, cobalt glass boasts a stunning visual appeal while still providing moderate light protection when paired with proper storage.