Unexpectedly, the manganese dioxide transforms into a pink or purple tint when exposed to ultra violet rays from the sun. So most glass that “purples” can be dated between 1880 and WWI. Now you knooooow!
Manganese glass will turn purple after a long exposure to uv light. People will set it out in the sun for a long time and it will start turning a shade of purple. The longer it's left out, the deeper the purple will get.
It is manganese that will cause glass to turn purple if exposed to the sun for a period of time. My parents collected all kinds of items and we went to old dumps where they would dig for bottles. My Mother would then put some of the bottles in the sun to get them to turn purple.
Glass that contains manganese will turn lavender when exposed to UV light over time. When I say time, I mean years of exposure to sunlight. 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.
Colored Glass Knobs
Perhaps the most unique is uranium glass, which gets its yellow-green color from trace amounts of uranium in the mold, creating a subtle glow under ultraviolet light.
As uranium glass was used to manufacture household items, some pieces are incredibly common and can be picked up at a relatively low price.
With the nation recovering from World War II, the 1950's were a more prosperous time and metal knobs replaced glass as the door and cabinet hardware of choice in most modern homes.
Manganese was used in tableware by 1865 and in flat (window) glass in the U.S. long before 1880. A practical end date for manganese use in all but specialty bottles is about 1920, although some use continued until the early 1930s.
Manganese deficiency in broadleaves causes new leaves to be yellow to whitish with relatively wide, green areas along the veins. On severely affected leaves, brown dead spots develop between veins. Leaf margins may become crinkled, curled, or wavy, and shoot growth can be reduced.
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.
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.
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.
During the mid and later 1800s virtually all American glass companies were using manganese in their glass formula. Around 1915 the use of manganese was discontinued and selenium became the chemical of choice as a clarifying & stabilizing agent.
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.
ADCA president Paul Woodfin says that a 19th century doorknob can sell for anywhere from $20 to hundreds of dollars. If you have a high-quality antique bronze doorknob in good condition, you may be in luck — Woodfin claims these can net you a payday of over $1,000.
There is clear evidence from studies of humans exposed to manganese dusts in mines and factories that inhalation of high levels of manganese can lead to a series of serious and ultimately disabling neurological effects in humans. This disease, termed manganism, typically begins with feelings of weakness and lethargy.
How is manganese deficiency treated? Treatment typically involves increasing manganese intake through dietary changes or supplements under the guidance of a healthcare professional. In severe cases, medical intervention may be necessary.
Manganese in the glass recipe reacting with UV radiation from the Sun. So you will rarely dig a purple bottle, unless it was in the Sun before getting buried. Set em out in the sunniest spot and wait a few months for any to show signs of purple.
Use a 2% solution of Citranox® Liquid Acid Cleaner and Detergent (2.5 oz/gal or 20 mL/L) followed by a thorough rinse to remove Manganese Oxide from glassware.
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.
It must also be operable with one hand and without tight grasping, pinching, or twisting of the wrist. Lever handles and some other types comply with this requirement. Traditional round doorknobs are not accessible, as they require tight grasping and twisting to turn.
Glass is made from melted sand. To make crystal, lead oxide and other elements are introduced during glassmaking to make silica glass. Crystal interior door knobs are heavier than glass, giving the door knob more heft and feel when used. Crystal door knobs also reflect light better than glass.
Some older doors have knobs in the middle because the symmetry of this design was popular in many parts of Europe. On 1stDibs, you'll find a large collection of antique and modern doors from some of the world's top sellers.