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Lightning in a Bottle Part 2

Updated: Aug 25, 2023

Hey there, Xplorers! Welcome to Part 2.

If you were with us last week, you know that we’ve just started a series of blog posts on one of our very favorite topics here at TerraX — glass bottles (or containers to be exact).

glass bottles, green bottle, historic artifact

Glass bottles can be found just about anywhere, and they’re always fascinating! They offer a peek into the lives of people who lived before us. Did they drink a lot of soda? Did they have enough money to afford perfume? Maybe they ran a still and bottled whiskey. When we recover bottles and bottle fragments at our project sites, we can only expand our pool of data and learn more about the cultural history we share here in the southeast.

However, the key to bottle analysis is learning about the different features of any bottles. Whether a bottle has a cracked off or a tooled finish, a flat bottom or a rounded bottom, colorless glass or milk glass — all hints about when, where, and why the bottle was produced. Now, last week, we went through the first three bottle characteristics to look for — shape, color, and the finish or closure. (Don’t worry, we’ll review those in a minute.) Today, we’re going over the other three — body and seams, the base, and maker’s marks. Plus, we’re taking a look at one of the most well-known bottles that you’ve definitely heard of.

Before we dive back in, we just want to issue a quick reminder about the Society for Historical Archaeology’s Historic Glass Bottle Identification and Information website. We love their site and use it all the time, and we recommend you check it out too.

Alright, are you ready? Let’s dig deeper!

Let’s Review

historic glass, archaeology, blue glass, green glass

Before we dive into today’s bottle features, let’s quickly review what we covered last week. In Part 1, we started by talking about shape. Bottles, of course, come in all kinds of crazy shapes, and those shapes give us a clue as to what they were used for. For example, whiskey or other liquor bottles tend to have wider, flatter fronts where a label or embossment would have been placed to label the bottle, but soda bottles tended to be thinner and rounder. Beauty products typically come in wide-mouth, squat jars while sauce bottles usually have a thin neck and small mouth. Shape can tell you a lot!

Then there’s color. Glass comes in all kinds of colors from dark blue all the way to translucent milk glass. Remember — the key here is that “clear” glass — i.e. glass with no color — is referred to as “colorless.”

broken glass bottles

And finally, last week, we talked about finishes and closures. We won’t go over every single type, but remember — some bottles are mouth-blown, others are mouth-blown and then finished with a tool, and others are made by machine. Mouth-blown finishes tend to be a little bit asymmetrical and are more likely to contain air bubbles and other imperfections while machine-blown finishes are standardized and nearly perfect every time. Also, bottle-making technology naturally improved over time, so completely-mouth-blown bottles tend to be older than machine-made bottles.

At the end of the day, glass bottles are important to archaeologists precisely because they have so many identifying features that can help us narrow down exactly when those bottles were produced. Because we can often identify when bottles were made down to a range of only a few decades, we can use that information to more accurately date whole archaeological sites. Discovering when an artifact assemblage is from is a HUGE part of what we do, and glass bottles are a reliable way to make that task easy!

Okay, still with us? Good! In that case, let’s move on to our new bottle features for this week.

Body and Seams

If you take a close look at the side of a glass bottle, you’re likely to find characteristic features that provide clues as to how the bottles were made. And, of course, if you can narrow down how a bottle was made, you can narrow down when it was made. Bada bing, bada boom! Archaeology is easy! (Okay no, not really.)

yellow bottle, 2 centimeters, SHA, bottle neck
Photo courtesy of the SHA site again — Can you see how the neck was twisted?

If you notice that a bottle has bubbles in it or you can see where the side seams have faded because the glass was twisted by a tool, it was definitely mouth-blown and made before machines automated the process of making standardized, ideally proportioned and uniform bottles. On the other hand, if you notice that the bottle seems perfectly straight and evenly proportioned and that the seam or seams on the sides go all the way up to the top, you definitely have a machine-made bottle.


Bottle bases can usually fit into one of two categories. Gee, I wonder — could they be mouth-blown and machine-made? Alright, sassy! We’re just glad you’re getting it!

It’s true — you can typically spot a mouth-blown bottle base a mile away. Mouth-blown bottle bases often have air bubbles and small scars on them from the tools used by the glass blower. They’re also usually not totally symmetrical, which, of course, is part of their charm. There are also some weird bases out there that are actually rounded instead of flat.

SHA, warped glass bottle
Photo courtesy of the SHA website

(Okay, fun sidenote time.) It’s true! They’re kind of a unique case, and they’re not super common, but round-bottom bottles are actually a thing. In the late nineteenth century, bottle makers had to contend with a unique problem. At that time, carbonated drinks like soda and mineral water were stored in corked bottles. If such bottles were left upright, the corks would often dry out and shrink, and the drinks would lose their carbonation or evaporate. So, those bottles were made with round bottoms so they would lie sideways. It may have been a nuisance at the time, but rounded bases are super helpful for archaeologists today. When we find round-bottomed bases, we know they were manufactured roughly between 1870 and 1910. (We’ll be sure to revisit these later!)

Machine-made bottles, perhaps unsurprisingly, are much more uniform, and though they do often have scars or marks left by the machinery, even those are symmetrical. For example, some machine-made bases have suction scars and some have ejection marks from where they were touched by machines during the manufacturing process. However, these are neat and round, unlike the more lopsided mouth-blown marks. Just as with the side of the bottle, the seams are a crucial clue to understanding how the base of these glass containers were produced.

Maker’s Marks

There’s just one more feature of glass bottles you need to know about, and this one might be our favorite: Maker’s marks.

Maker’s marks are small symbols, often containing letters or even whole words, that are embossed, stamped, or otherwise written on glass bottles to identify the company and/or factory that produced them. They’re kind of like logos in that way — each company has a unique maker’s mark, and while maybe maker’s marks for glass bottle factories are not quite as famous or recognizable as, say, the logos for McDonalds or Toyota, they are just as clear identifiers for their companies.

A couple of examples of maker's marks, again courtesy of the SHA website

As you can probably imagine, maker’s marks are incredibly helpful for identifying bottles and discovering more about where and how they originated. It’s easy to search for a maker’s mark on a bottle or bottle fragment (the SHA’s catalog of maker’s marks is fantastic and so simple to use), and discover what company manufactured your bottle. From there, you’re a Google search away from looking up that company and discovering more about where they are or were, their years of operation, their bottle-making methods, and so on.

Let’s Talk About an Old Favorite — The Coca-Cola Bottle!

glass coke bottle, clear glass bottle
There's that classic Coke bottle in the middle!

We know it, we love it — the Coca-Cola bottle. It’s an icon! People all over the world recognize Coke’s classic branding. After all, it’s literally everywhere. (We told you you’ve definitely seen this one before!)

As you can imagine, as archaeologists, we find Coke bottles all the time. As America’s favorite soft drink for — we don’t know, like, a million years? — it’s really no surprise the old Coke bottles are all over everywhere. But wait…

Over its many-year history, Coke has changed up its branding a little bit. Bottles haven’t always had the iconic red plastic labels! What’s more, often glass bottles don’t survive all in one piece. All too often we only find a broken piece or two, and they don’t always come with a clearly identifiable embossed “Coca-Cola” either! So, how can we distinguish Coke bottles from the rest?

By looking at our six features, of course! When it comes to Coke bottles, the two most important are color and shape.

vintage glass coke bottle

Remember how we said glass bottles can come in many different colors, even several different shades of green? Well, when the Coca-Cola company set out to create a unique bottle that anyone could recognize, they created and trademarked a whole new shade. In fact, the color was so unique, we literally call it Coke-bottle green! Now, since Coke started using Coke-bottle green, other companies slowly started using it too, but — good news — those fluted ridges we talked about just a minute ago are still unique to Coke. So, if you’re looking at a bottle or bottle fragment in this exact color and it has those unique ridges, it’s definitely Coke.

Coke bottles also have a special and highly recognizable shape. Look at the sides of the bottle body. Do you see the little ridges that run vertically all the way around on the sides? That fluted shape is also totally unique to Coke! If you’re holding an antique bottle with fluted sides, you’ve got yourself a Coke bottle, Xplorer!

What Questions Do You Have?

Congratulations, Xplorer! You’ve made it through Glass Bottles 101. Now, you have all the knowledge and tools you need to start practicing your own bottle analysis skills. Take a look around your house, and if you don’t have any glass bottles there, visit your local antique store — bottles are usually plentiful there! Take a look around, and see what features you can identify! Can you narrow down a bottle to a specific factory, company, or decade? What can you learn?

And what questions do you have? We’ve covered a TON of information these last two weeks, so we’re sure your heads are spinning a little bit! (Trust us, ours still spin sometimes too.) What else do you want to know about bottle analysis? Let us know on social media! As always, we’re on Facebook, Instagram, and LinkedIn, and you already know we love hearing from you!

We’ll catch you next time, Xplorers. Keep analyzing bottles!

— The TerraX Team


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