Purple Glass bottle

zmalonw

I found a slightly purple glass bottle this weekend. It has 10 sides and there is a star with a s inside along with a 13 right below it. I cant find much on it other than bein a Southern Glass Co made between 1916 and 1931

historic

Got photos?

Soda bottle maybe?

zmalonw

Here are a few. There is a very faint purple tint to it. Im thinkin it started life as a clear bottle.
http://i899.photobucket.com/albums/ac191/ZachMalone/IMG_3827.jpg
http://i899.photobucket.com/albums/ac191/ZachMalone/IMG_3825.jpg

historic

A picture says it all. This ad is from 1929 - your bottle may be a bit earlier or later of course.

The presence of manganese in some form in the glass causes glass to turn purple when exposed to UV /sunlight. The purple may become darker if you keep the bottle in bright sun over time.

zmalonw

Right on! Thank you for the info

BobB

A slight purple tint to clear glass is frequently because of the presence of manganese put in the glass batch as a “decolorizer” (to mask the bluish/greenish/brown color of impurities like iron) – except purple manganese itself will color the glass if exposed to the rays of extensive sunlight. Sometimes called “sun burned”. Because some people think the purple coloration makes it look more antique or rustic/country, there is an industry in the American southwest where collectors can send boxes of old glass, this glass is set out in the desert to cook for some weeks, then sent back “sun burned” purple. Story goes that American glass makers used manganese until their primary source (Germany) was shut off by WWI, so when companies ran out of manganese, they changed their recipes to use arsenic or another decolorizing agent in their mix. BobB

historic

Actually, bottles are exposed to radiation at food processing plants. I know the person here in the northeast who is doing this on a large scale - the irradiating is done in Massachusetts.

It is my understanding that even in strong sun, the color change takes quite a long time.

BobB

The cause is the same -- i believe it is alpha radiation but several pseudo-experts I just checked claim it to be the ultraviolet part of the light spectrum. By both sun-exposure & irradiation, it is manganese used as a decolorizing agent that turns amethyst purple. The story has been told so many times by so many well-intentioned but un-scientific collectors that the details get blurred (I just spotted a website with one version of the story claiming Magnesium ! is the chemical. No, Manganese, not Magnesium!) But this source does point to the presumed year 1915 as the cutoff for when American clear glass chemistry changed to use a different decolorizing agent; I suggest arsenic, this source says selenium, I think both have actually been used, but not Magnesium.
Through all this discussion, I do not know for sure how much bottle glass would have been "improved" by the use of a decolorizing agent; bottles are not my thing but I expect that the manganese / arsenic / selenium used in improving crystal glass used in making goblets, bowls & vases was probably not used as much in bottle-making, --where clarifying the glass to make it less discolored was not a major concern when mass-producing cheap condiment containers. When I find a potential goblet or decanter for my collection and I detect purpling, that's the kiss of death -- it's poor glass or it has been mistreated (or both), proving it is not worthy of a fine antique collection. BobB
See Elaine Henderson's website http://www.patternglass.com/sunpurple.htm ...her home is Phoenix AZ where every antique shop has old purple glass, real-fake-reproduction.

CJay

bottles were decolored so consumers could SEE the product more appealingly...since food, etc. looks Better thru "clear" (colorless) glass than aqua-tinted (natural color of glass). Manganese use was discontinued around 1920 as a decolorant primarily because it did not work too well in bottle making machines (less than 15% of the manganese came from Germany, so WWI wasnt the reason for its discontinuance). Some small scaled manufacturers or those still blowing by mouth continued using it however for a few years more. And glassware vessels may have had it in their formula till the 1930s. ???
See this article for More info:
Lockhart, Bill
2006 The Color Purple: Dating Solarized Amethyst Glass Containers. Historical Archaeology 40(2):45-56.

BobB

Thanks for this cite, CJay. I'll hope to look it up when I next get over to the university. The technology of the bottle making machine isn't among my strengths, but this correlation makes sense. I have often seen pieces of the late-late pressed pattern glass (ca.1910-1925) in which the presumably clear glass was murky grey-purple and this suggested to me that the switch from pot to tank furnaces made the earlier (manganese) recipe unsustainable when cooked in the tank. And the new bottle making technology, of course, is based on continuous tank feed. So bottle makers changed their recipe during this period while the pressed table glassware industry went the way of the dinosaur. BobB