My WAG is as others have said that they indicate the mold that the jar came from. If a pattern of defective jars starts to emerge they can determine if they are from the same mold.
From the website of United Glass, UK:
More here, too
The Illuminati are behind many of life’s mysteries. Bottle bumps appear to be just one more.
I wonder if it has ever occured that all bottles from a certain mold were recalled from shop shelves due to some form of contamination. I would love to see the memo:
“Please return to the manaufacturer all bottles of Budweiser with the section code: oo ooo oo o”
Must be the stuff of nightmares for people who work in off licences and bars.
Actually, it is Braille-the message being, “Open opposite end, meathead.”
I actually have a certificate of completion of a “Education in the glass making process” or some such title hanging in my cubicle at work from Saint Gobain containers. 
The bumps on the bottom of glass jars/bottles towards the edge of the bottle (outermost part) are called knurling. They usually look like small lines pointing in towards the punt. The smaller dots towards the center and often inside the punt are called the baffle.
They are not a by-product of the manufacturing process of the glass. They are intentionally part of the glass mold. They keep the glass stable on a manufacturing (bottling) line’s conveyor belt.
We actually had a couple of lots of glass with the knurling slightly off. Our lines were shut down for a day, bottles were falling all over the place.
Except, of course, after reading this again, I see that you are actually asking about something entirely different.
(Damn Sierra Nevada.)
Numbers, or a combination of numbers and letters is a glass mold.
A group of small dots, or sometimes, a deep groove, are spotting lugs. They are used to line up labels anywhere on the bottle except directly centered on the seam of the mold.
I just checked a few bottles and the labels are pasted on randomly, with no apparent relationship to the dots.
I am going with the **nametag **and **sage rat **evidence that the dots are mould identification for quality assurance.
Probably a wise decision, considering the number of bottles I handled myself last night.
I have some coffee jars made by Brockway Glass ca 1981. I worked in the coffee plant and I took these for food storage jars. They have no bumps on the side of the jar, but have various single digit numbers on the bottom which I assume to be mold numbers. They also have a four digit number which is common to all which I assume is a date code. I can’t decipher it though. It is 5498.
I just checked one of the jars in my cabinet. It’s oddly shaped, so it bows out at the end, and the dots are more on the side than the bottom, so that rules out the friction reducing theory.
You quick guessers might want to take another look at psycat90’s credentials and answers. It sounds like the voice of one who knows.
Clearly a more comprehensive survey is called for. I dug through all my glass jars, and found at least some order. It appears that dots may be immediately adjacent to each other, a short distance apart (2 dashes in the list below), and a long distance apart (4 dashes). Within the post, spaces are autoformatted (shrunk) so that the number of spaces can’t be distinguished. This was the reason for replacing the spaces with dashes.
Anyway, following this convention, the codes appear to all be exactly the same length. With the exception of the last four on the list, which also showed more variation in the spacing - some dots seemed to be the equivalent of 3 spaces apart.
oo–o----o–ooooo–Smucker’s Red Raspberry Spreadable Fruit, 10 oz
ooooo----o----ooo–Smucker’s Black Raspberry Spreadable Fruit, 10 oz
oooo–o----oo–oo–Great Value (WalMart rebranded) Worcestershire Sauce, 10 fl oz
oooo–oo----o–oo–Bama Pineapple Preserves, 16 fl oz
ooooo–o--o----oo–Simon Fischer Lekvar Prune Butter, 17 oz
oooo----o----oooo–Mt. Olive Hot Dog Relish, 12 fl oz
oooo–oo–o----oo–Mt. Olive Dill Relish, 8 fl oz
oo–o----o–ooooo–Mt. Olive Hot Chow Chow, 16 fl oz
ooo–ooo----o–oo–Cates Mild Chow Chow, 16 fl oz
ooooo–o----o–oo–Pomona Sunshine Pickled Peaches, 22 oz
oooo----oo–o--oo–El Torito Medium Restaurant Salsa, 24 oz
oooo–o----o–ooo–Braswell’s Green Tomato Relish, 8 fl oz
ooo–ooo–o----oo–Braswell’s Green Pepper Jelly, 10.5 oz (same size jar as above)
oooo–oo–o----oo–Spice Islands Dill Weed, 1 oz
oooo–oo----o–oo–Bolla Pinot Grigio, 750ml
o o o o oo oo–Ecco Domani Pinot Grigio, 750ml
o-- o–oo----o–o--oo–Southern Comfort, 375 ml, circa 1996 - dots on concave portion of curved flask
o–oo–o--oo–o----oo–Heinz Tomato Ketchup, 14 oz
o–oo–o----o–o--oo–Heinz Chili Sauce, 12 oz
With the exception of the Southern Comfort, all the bottles were essentially round at the bottom. My bottles with angled bases did not have the dot code.
Also, my more recent bottles from Braswell’s do not have the dots.
About half of the bottles have the dots repeated on the opposite side of the bottle.
With regard to lining up the label, there did not seem to be any association with the edge or center of the label, and the edge or center of the dots. I doubt it would matter in any case - a label’s horizontal position shouldn’t matter on a round bottle. Other than the Southern Comfort, the only bottle that was squarish in its body was the El Torito jar, where the label did indeed begin in line with the edge of the dots. However, this could easily be random chance.
If vertical alignment is the concern, the bottom or top of the bottle would be a better guide.
Imperical evidence that lables have nothign to do with it.
We have several folks stating that the lables are in different places in regards to the bumps, often on the same product.
I have, on my table, a Kerr home canning jar that I keep pens in. It has bumps (000 0000 0 00) despite the fact that it would not have been intended to have a labelling machine put a label on.
I’m leaning towards going with Nametag on this one.
Hey, they wrote back!
Awesome!
I asked our sales rep this morning, she confirmed it was exactly what the site that Nametag linked to described it as.
And that spotting lugs are generally only in molds that require an exact location of a label, like for instance, something with a cartouche or an etched design that a label would be centered under.
Nifty.
And I need to sign up for “Introduction to Glass Container Technology” class again. :smack:
The dots down toward the base of your glass bottle is a coding system used by the glass manufacturer. It helps them to identify the mold cavity the bottle was produced from. The indentations on the underside of the bottle help to line up the bottle during the labeling or printing process.
Hi mistybrighteyes, welcome to SD.
Some notes: somebody will probably make a zombie joke, because, if you notice, this thread died 11 years ago, until you disturbed its quiet repose.
Also, try to read the thread particularly in a zombie, if there are mods lurking about: unless info is new, they’ll usually drive a stake through its heart, and lock it for good, which means tasty bits of it still left over can never be gnawed at again. (Mmmm, zombie bits.)
Also, you may notice that what you post has been said, repeatedly in this case, before.
Done and done.
Now, my tasty bit:
So spotting lugs and knurling are the same thing?
ETA: as gerunds, these sound like fun sports. Something on ice with logs?
Pretty sure whatever was in those jars has expired by now…