It is generally accepted that the ultra-violet light initiates an electron exchange between the manganese and iron ions. This changes the manganese compound into a form that causes the glass to turn purple.
Because it takes so long, some people expose the glass to UVC lamps in a box at high intensity for 3–4 weeks to get them to change from clear to lavender.
The first collector to attempt dating purple glass was Grace Kendrick (1963:54–56). Ken- drick dated the phenomenon of “sun-colored glass” as lasting from 1880 to 1914.
Chemical description
However, in large quantities, glass treated with manganese dioxide photo-oxidizes when exposed to ultra-violet sunlight over a period of years to decades. The result is glass that changes from a clear to a lavender-purple color.
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.
Following the Cold War, restrictions on uranium glass were completely lifted. During this time many older pieces entered the free market and new pieces continued to be produced in small quantities into the 2000s.
For the radiation to turn quartz purple, the quartz must contain trace amounts of iron. The color change is due to the fact that the radiation exposure results in an oxidation of the iron impurities (Fe+3 to Fe+4) which changes the absorption spectrum.
If there is no mark on the glass, there may be other signs that can help you work out how old it is. It may have mould marks, show the pontil mark of blown glass or have identifying characters within the glass, such as bubbles. All of these can help you find out more about your glassware with a bit of research.
Glass is particularly susceptible to radiation-induced coloration/discoloration due to its amorphous, non-crystalline structure. The nature of the optical changes vary, but usually consist of coloration in the visible light region and the formation of absorption bands in the infrared and/or ultraviolet regions.
Purple glass is made from the metal oxide manganese, which is added to the batch ingredients. Many glass manufacturers, such as the Imperial Glass Company, produced purple glass. It is also possible that your glass piece might once have been clear but turned purple when exposed to the sun.
It is simply caused by alkali (soluble salt) being leached from the glass by slightly acidic water and then forming fine layers that eventually separate slightly or flake off causing a prism effect on light bouncing off and passing through the surface which reflects light differently, resulting in an iridescent ...
Over time, UV rays will weaken and breakdown these dyes resulting in a purple appearance. If you want to avoid purpling of your window films, you will need to buy high-quality coatings, preferably coatings which have been metalized and are thus more stable.
Neodymium Glass (365nm / 395nm)
Neodymium glass (sometimes referred to as Alexandrite glass), changes color according to different lighting conditions. The glass appears lilac (or sometimes pink) in natural sunlight or yellow incandescent light, and smoky blue in fluorescent/white light.
Pink and crystal (clear) are two of the rarest colors of Depression glass.
The best practice when approaching vintage glassware is to steer clear from using it on a daily basis, and don't store things in it for a long period of time, Dr. Kosnett recommends.
Depression glass is the term for the colored or transparent glassware that was mass-produced in the United States during the 1920s and 1930s. Pink and green are the best-known colors, but you can also find it in red, amber, yellow, blue, white, and clear.
Solarization of Glass
An interesting characteristic of colorless glasses which contain manganese dioxide as a decolorizer is their tendency to turn different shades of purple when exposed to the rays of the sun or to other ultra-violet sources. It is a photochemical phenomenon that is not yet perfectly understood.
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.
Quartz, one of the most abundant minerals in the Earth's crust, is composed of silicon and oxygen and in its pure state is colorless. When iron replaces some of the silicon atoms, the color is purple.
Uranium glass is considered to be radioactive, but the level of radioactivity is very low. This generally means that there are no negative health impacts when you handle the glass correctly.
However, since uranium is radioactive, you can also be exposed to its radiation if you are near it. Even if you are exposed to uranium, you might not be harmed. Whether you are harmed will depend on such factors as the dose (how much), the duration (how long), and how you happen to contact it.