Metals that had been previously used for doorknobs , such as iron, brass and bronze, were needed to manufacture airplanes and other necessities for the war. Prices for vintage glass knobs vary widely, depending on condition, rarity, style, and color. Why do old glass bottles turn purple? Category: hobbies and interests beadwork. How can you tell how old a glass bottle is?
What makes old glass blue? Is there purple Depression glass? Indiana Glass Company. What makes purple glass purple? How do you make purple glass? What is manganese glass? Does glass change color over time? What color is glass naturally? What is the rarest color of Depression glass? Why is it called Depression glass?
What is black amethyst glass? What does EAPG mean in glassware? I would like to know if Glassware made in a factory can also be reversed, like Fostoria and Cambridge and Heisey glass, most all their glass in clear will turn purple and I would like to know if that too can be reversed. Thank you for reading and I hope to hear back from you soon.
I hope you will send me an email,and maybe if there is a site that people can go to and see how this is done. BUT the process is risky, involving very slow, gradual heating to a high temperature in an oven, over a number of hours. And it may or may not have any effect depending on the piece involved. The possibility of breakage is always present. There might be other ways. I am not sure about this. Personally, I would NOT recommend any effort to try reversing the color changes, but that is only my own opinion.
Thank you for writing! Thus, it is possible that their purple or sun-colored glass manufactured during this early time period could also be altered by thermal treatment…but, as pointed out, there are many variables associated with the glass chemistry and manufacturing process that could affect the result of such.
As these three companies made more expensive and higher quality glass items, their glass formulations might not respond to thermal treatments as the cheaper glass formulations would. All attempts have been successful with zero failures so far…. Hi James, I know this is addressed specifically to Rick, but may I interject as well….. Also, what color were the circa s beer bottles, before and after? Can you provide some sources that give more detail on the specifics of these cases? Thanks and take care, David.
Hi James, Thanks a lot for your info. Hi there! I know that purpling antique glass is a controversial topic obviously , but I feel I must speak out as a collector. I started hunting for old bottles back in the early 80s with my Dad in the ghost towns and mining camps of the western U.
I have come across several old bottles and jars over the years that turned a beautiful DARK purple by nothing more than good old sunshine! To say that ALL deep amethyst glass has been artificially irradiated is absolutely ludicrous! The amount of manganese that was added to any given batch of glass prior to , was haphazard to say the least. Some glass when exposed to ultraviolet rays will only slightly purple to a faint pink tint, while others will turn the deepest royal purple.
Also the amount of time the glass has been exposed is also a factor… I have set clear glass bottles by on my window sills, and within two weeks they have already begun to purple! However, I will stand by one of my main points, which would be this observation: If you run across a large accumulation or collection of dark purpled glass for sale by one specific dealer at a flea market or antique mall, you can be pretty certain they were irradiated.
I have seen this a number of times at various venues in the Midwest. In all cases, the glassware had been irradiated, and there was a mix of bottles, jars, flasks, and maybe a few insulators or other items such as lamps or other EAPG mixed in the inventory that were not in their original colors.
Thanks very much for your post. I appreciate your thoughts! Maybe you could enlighten me about a compote I bought. It appears to be mid century and is a clear, pale purple lilac? The weird part is that it glows bright green under a black light! I thought uranium glass was usually green or yellowish.
Any ideas about what is going on? My address is listed on the right hand bottom corner of the page. Best regards, David. Another name for it is Alexandrite. Neodymium is a rare earth metal used to color class and it changes cplor under different types of lighting. So is sun purpled maganese glass but sea glass collectors frown upon anything altered manuallty and not by mother nature. Neodymium glass was made to be that color.
My purple bottle collection is at 31 as of right now, but what I gather from your article is, they are all fake? I know this subject is very confusing, and there is alot of misinformation out there.
The color of some irradiated bottles will gradually fade over time, if left out in the sun for several months. If you can, please contact me through my email address lower right corner of any page on the site and send me some pics of the bottles. Thanks, David. Hi Dan, Since this is a free country so far , you are welcome to say and believe anything you want to. I will admit that there are many purple bottles, jars and other glassware that were made in a purple color to begin with and have always been that color from the beginning.
Bobby Glass, it might be and it may have been glass that was purple originally. One possible way to tell would take time and I don't know how much time. We do restoration work on churches and often run into glass that has had parts of pieces covered by lead or moldings and the glass is still perfectly clear where the lead or moldings around the leader panel kept that section from UV exposure. So you could take some and tape off a bit with some light safe tape probably electrical, duck, etc.
Although, I also don't know if the glass reaches a certain stage of purple and then never gets any darker? I'm thinking that may be the case as they are always pretty close to that same shade. Any idea why, when heated in a torch, the purple disappears and the glass turns clear again?
Same happened with red glass though I'm certain the red started out that color, and wasn't discoloration due to UV. Thank you all for your comments! I have a pair of glass candlestick holders that display a purple tone to them. Does this mean that they would have been made in late 19th to early 20th century?
Add a public comment to this entry. To ask a new question, submit form at libanswers. Ask a Glass Question. Ask a Glass Question Question. Which of the following BEST describes your question? Selected Files:. Check to receive an email confirmation of your submission. Later chemists introduced pyrolusite into the making of glass to balance impurities. For example, if the sand used to create glass contained traces of iron, the untreated glass produced would have a yellow appearance. The introduction of pyrolusite would balance the yellow tint with purple, causing the final glass product to be clear in appearance.
The element manganese found within glass will remain colorless as long as it does not oxidize to form manganese oxide.
However, radiation from the sun will cause manganese to oxidize. Glass exposed to sunlight for a long period of time will turn purple if it contains manganese. However, glass that contains manganese that is not exposed to sunlight, UV light or other forms of radiation will retain its clear appearance. Tin Oxide Uses.
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