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How to Date Owens-Illinois Glass
If you are an avid beach glass collector, or a collector of glass bottles, jars, cups, etc, you may have noticed an odd symbol and/or numbers on your find and didn't know what they meant. I am here to clarify a bit of the mystery. Usually, the symbols are a logo for a company, and the numbers a code for where and when the particular glass item was produced. Each glass making company has their own method of labeling their products. With this hub, I am going to focus on the methods used by the Owens-Illinois (O-I) Company, and show you how to date your glass finds using the symbols and numbers indicative of the O-I company. I am by no means an expert on the numbers, nor am I an expert on how to date glass using the numbers, but I have done a lot of research on the subject, and I am relaying the information I have acquired along my internet travels.
What first led me down this path of discovery was a small piece of glass I found washed up on my local creek with the word Duraglas embossed on it (Exhibit A). Duraglas was the name given to a process used by the Owens-Illinois Glass Company, “where the surface of the hot, just produced bottles, were sprayed on the body, shoulder, and neck (not base or the top of the finish) with a stannic chloride (Tin (IV) chloride) vapor that allowed the tin to bond to the outer surface providing scratch resistance and durability to the bottles." (Lindsey, B.) Though this process is still in use today, the word Duraglas was embossed on bottles only between 1940 and the mid-1950s (Lindsey, B). Therefore the piece of glass I found was manufactured using this process somewhere in that time frame. However, without having more of the glass, I am unable to narrow that down to a specific year.
How Glass Bottles and Jars are Made at Owens-Illinois
History of the Owens-Illinois Glass Company
If that was the end of it, this would be a pretty lame blog post, but as it stands I am a fairly curious person and couldn't help digging a little deeper. (I am also a giant nerd and find this stuff fascinating.) I will never know exactly what year the previous glass was manufactured, but while digging I discovered that I owned pieces, that with a lot of persistence, could be dated to a specific year.
But first a little about the Owens-Illinois Glass Co. The history is a little confusing, and as is usual of the internet, varies from website to website, with each website having their own sources, and their own account of what happened. I’ll gloss over all that and share what seems the most accurate.
According to the Owens-Illinois Glass Company website, the founder of the company was Michael J. Owens, who invented the automatic bottle-making machine around the turn of the 19th century. You can guess from the title of machine what it did. The automatic bottle-making machine revolutionized the industry, and became the foundation of today’s glassmaking industry. As a result of the machine's success, and with the accumulation of a series of smaller companies, the Owens Bottle Co (1911-1929) grew into a prominent business.
In 1929, the Owens Bottle Co. merged with the Illinois Glass Co. forming the company it is now (with a few changes along the way). Currently the company is the largest manufacturer of glass containers in North America, South America, Asia-Pacific, and Europe, with 79 plants in 21 countries. According to Wikipedia, approximately one out of every two glass containers made worldwide is made by O-I, its affiliates, or its licenses.
1930 to Mid-1950s
Shortly after the Owens-Illinois Glass Co. merged into existence, the company began utilizing a new symbol to mark their products for identification purposes of recycled bottles, and for various other reasons. The symbol, seen in the pictures below labeled Exhibit B and Exhibit C, contains an I inside an oval with an elongated diamond superimposed over it. (Sorry I don't have better pictures, the glass is quite old and had been in the water for quite some time.The symbols, therefore, are quite faded.) Production of this particular mark ended somewhere in the mid 1950’s. There is no exact year in which production of the symbol stopped, as various plants ended use of the mark at different years.
Now, I know from the use of the symbol on the glass that both pieces pre-date the mid-1950s, but is there a way to narrow that down? Yes there is. The general rule when dating glass with the O-I symbol is the number to the left of the symbol is the plant code, and to the right of the symbol lies the date code. Other numbers, such as the 7 in Exhibit C, are specific to the production plant, and letters, such as the A in Exhibit E, usually stand for the glass model (e.g. an A may mean soda bottle, etc.) In other words, they're not very useful for our purposes. The number on the right is our year code and what we are most interested in.
The year code for Exhibit C is clearly a 9. In conjunction with the relative dates of the symbol, we know that the 9 could either stand for 1939 or 1949 (1959 is possible, but very unlikely). By the time 1940 came along, the company realized year codes were beginning to repeat, so in the 40's they implemented adding a period after the date code to indicate years 1940 -1949. By the mid-40's most plants switched to using a two number date code (such as 46 for a production year of 1946). However, use of the period after the one number date code in the 40's, and use of the two digit year code was inconsistently used by various production plants, therefore the 9 alone doesn't always mean 1939 with absolute certainty. (Lindsey, B) There is one factor, though, we have yet to consider: the thickness of the glass.
In 1941, the United States of America formally entered World War II on both the Pacific and European fronts. Resources became limited as many industries focused on manufacturing supplies to support the war effort. As a conservation measure during the war, the amount of glass used for many bottle types was reduced. You can't really tell from the picture, but the green glass in Exhibit C is quite thick, thicker than anything we would see today, which leads me to believe that the glass was indeed manufactured in 1939, and has been sitting in the creek ever since, waiting for me to find it.
Exhibit B is another story all together. I only have half of the picture. The number in that picture could either be a 6 for the plant code, meaning it was made in Charleston, West Virginia, a plant that was in operation from 1930 - 1963 (Society for Historical Archaeology) or it could be a year code of 9. If it is a year code, the thickness of the glass and the lack of a period after the 9 suggests a manufacturing date of 1939.
Mid-1950's - Present
In the mid-50’s, the Owens-Illinois Glass Co. switched to a simpler symbol. They axed the diamond, and instead were left with a simple I inside of an O (see pictures to the right and below). The general trend, however, remained the same with the plant code on the left of the symbol, and a date code to the right. Our first example to the right (Exhibit D), fortunately for me, is extremely easy to determine the date of production. Since 2063 has yet to pass, and the company did not exist in 1863 nor did it use that symbol prior to the 1950's, the only possible year of production is 1963.
However, this next piece of glass is not so easy. I am unsure of whether or not this particular example follows the general trend of date code to the right of the symbol. That 7 placed there could literally mean anything. If we assume that the 7 is indicative of a year, it could mean anything from 1957 to 2007. The plant code is of no use either to help narrow down the date. The number 17 is for a plant in Clarion, Pennsylvania which has been in operation since 1932 and is still presently producing bottles.
However, the A to the right of the 7 tells me that this piece of glass has a high probability of either once being a Coca-Cola bottle or a Pepsi-Cola bottle. If that is the case, this piece of glass may be our exception to the rule and the 7 to the right of the symbol may not be a year code at all. Coca-Cola and Pepsi-Cola didn't always adhere to the Owens-Illinois policies, and often had their dates on the heel, and not the bottom, of the glass. (Society for Historical Archaeology) However, what we do know is that Pepsi and Coke now come in plastic bottles or aluminum cans. They started the switch to plastic in the 60's and 70's. That narrows down the date from 1957 to 1977 if the 7 is indeed a year code. By comparing it to the 1963 glass, Exhibit E is more weathered. It is frostier and more scratched and appears to have been in the water longer than Exhibit D. This leads me to believe that the 7 stands for 1957. However, that is simply my best guess and not a certainty.
I know this was a long post, but I hoped you have all learned as much as I have. My sources are listed below, feel free to check them out yourself for more information on the subject.
1: Lindsey, Bill. "Bottle Dating." Machine Made Dating. N.p., 2013. Web. 05 Nov. 2013.
2:"Owens-Illinois Glass Company." SH. Society of Historical Archaeology, 2011. Web. 05 Nov. 2013. <http://www.sha.org/research/owens-Illinois_article.cfm>
3: "Owens-Illinois." Wikipedia. Wikimedia Foundation, 22 Oct. 2013. Web. 05 Nov. 2013. <http://en.wikipedia.org/wiki/Owens-Illinois>.
4: "Our Story - Leading Glass Manufacturer - Owens-Illinois | O-I." Our Story - Leading Glass Manufacturer - Owens-Illinois | O-I. N.p., 2013. Web. 05 Nov. 2013. <http://www.o-i.com/About-O-I/Our-Story/>.