What is the purpose of the row of braille-like bumps on glass jars and bottles?
These are found on the side of the bottle or jar at the very bottom. They are little raised dots in a pattern. A jar I have in front of me has the pattern … … . …
This sounds like a question that would have been asked before, but my searches have been fruitless.
I happen to have quite a few empty jars sitting here, that are all exactly the same size. The pattern is different on each one, there are copies on both sides, and they also have three labels, two on one side and one on the other. It intrigued me enough to transcribe them. I also threw in some other jars I had:
26 oz Ragu jars:
19 SG 95: oo ooo o o oo
27 SG 88: ooo oo oo oo
SG 20 95: oo o o ooooo
27 SG 95: ooo oo oo oo
SG 35 95: ooo oo oo oo
46 SG 95: ooo o o oo oo
32 oz Mayo jar:
SG 32 84: oo oo o oooo
14 oz jar:
04 88 SG: ooooo oo oo
Further investigation shows that SG is Saint-Gobain Containers (neat website). Still have no idea what the dots mean or how to read them.
First thing that springs to mind is to help stop them sliding about…?
And maybe to prevent liquid forming a seal and sticking them to the table.
But then why wouldn’t the pattern be the same on every jar?
Possibly coding used in the manufacturing process. Manufacturing either the jar itself, or more likely, in the food canning process. The bumps wouldn’t be easily human-readable, but a machine would have no such difficulties.
I was thinking mold codes, but three of SmackFu’s Ragu jar have the same pattern ( ooo oo oo oo). It doesn’t seem likely that he’d have gotten 3 jars made in the same mold.
Yes, I have misinterpeted the OP - my jar knowledge needs some work, it seems.
I thought they meant the pattern that the jar actually rests on, an inspection of a bunch of my jars reveals that this is a different thing (a kind of crenellation) - there aren’t any dot collections on any of them, as it turns out.
Glass jars sold in the UK also seem to have these patterns. Google isn’t being helpful in deciphering the code. 
Hey, I’ve got one too! Dolmio pasta sauce.
o ooo o
The only referrence to the bumps I could find was that they might be to do with recycling, each time the jar is re-used a bump is added so you know when it’s time to melt it down and make a new one. Sounds like complete nonsense to me and the post said that this was a wild guess and nobody really knew. I hold out hope of some doper coming up with the answer however.
At least we have learned one thing from this thread so far, SmackFu sure does love his Ragu.
Why not? Glass manufacture is a very efficient process and one machine can spit out jars at an enormous rate. You would not need more than a handfull of moulds for a given jar design at any one time.
I agree with Danalan. It’s most likely to do with the production line. A machine feels the bumps and therefore knows what label to stick on the jar, etc.
Errr…what? Why would that be an issue? It’s not like the machine gets a whole bunch of mixed shape jars and has to decide which label goes on what shape jar, or at least, that seems to me to be a pretty inefficient way of doing things…
Here’s a drawing of a bottle forming machine. It has 16 finish moulds.
It seems the bumps are not arranged in a binary fashion.
Using a piece of paper wrapped around the side of a bottle of beer I marked with a pen where the bumps are and then measured the spacing with a ruler. The spacings (in mm) for 8 dots are 4,5,6,9,5,3,7.
This long piece on bottle markings: The Dating Game doesn’t appear to answer the question.
However the article’s description of the types of info embossed on bottles makes me think that the collection of periods and spaces may be a plant code.
The glassmaking dictionary at http://www.glassonline.com/index.asp does not describe bottle codes.
I seriously doubt this. Commercial food packing lines don’t pack multiple varieties of food on the same equipment at the same time, so there is no need to differentiate between the jars and labels. You load the machines with matching jars and labels, and run them until you run out of product, then switch the line to a different product.
More likely it is a simpler answer; by reducing contact with the surface under the jar, the bumps reduce the friction when the jars are sliding through the races on the production line. The patterns are meaningless.
While there are bumps for this purpose they aren’t the bumps antechinus is asking about. On the side of a bottle, near the bottom, to the right of the maker’s mark is a series of oddly spaced and grouped dots. The full string of dots is about 1.5 inches long.
Glass bottles, too.
On a bottle of Lipton Green Tea with Honey:
17 1 05 CL-2 o o o o o oo o o 4
The 1 after the 17 has a circle around it.