Coatings & Surface Engineering

I may just be spit-balling here, but I'm guessing a lot of people don't drink as much water as they should. Enter the reusable water bottle - a great way to both save the environment, your wallet, or a few trips to the water fountain everyday while getting the fluids you need.

But what type of water bottle is best? As far as utility goes, plastic seems like a no-brainer (at least in my book). It's lightweight, durable, tasteless, easy to clean, (often) transparent, and more insulate (heat resistant) than metal. But we live in an imperfect world; chemical leaching and the BPA scare have deemed many plastics to be (skeptically) "unsafe". So what's a health-concerned person to do who wants a reusable bottle for their water (or Powerade/Gatorade, apple juice, goat milk, whatever floats your boat…)?

Well, back when I was searching for the right water bottle for myself a few weeks ago, I did a little research on other water bottle options besides injection molded plastics. The three realistic alternatives are stainless steel, aluminum, and glass. Let's take a quick look at each:

Stainless Steel

Stainless steel is steel alloyed with chromium (in a minimum amount of 10.5% by mass) to make it much more corrosion resistant. Stainless steel reusable water bottles are typically made from 18/8 alloy, meaning 18% chromium and 8% nickel. Unlike many other metals and materials, stainless steel does not leach any chemicals and has minimal problems with rusting or staining when in contact with water. Stainless steel bottles often have plastic (typically polypropylene) tops so you don't taste the metal or hurt your teeth if you hit a bump while drinking. Stainless steel is also very durable, lightweight, and easy to clean, making it ideal for hikers and office workers alike. However, it is metal, which means a few things: first, it heats up a lot faster than plastic. Second, it is still susceptible to some rusting and staining (especially low-quality stainless steel, though this can usually be cleaned off with a brush and good washing). Third, it makes a loud clanging sound when it hits things (I know, minor detail, but it is something).

NOTE: This clanging feature can also be used as a surefire way to annoy your hiking partner, should you position the bottle to make noise with ever motion of your pack…

OK, now that that's cleared up, onto aluminum…

Aluminum

Aluminum is a hard, lightweight metal that most people are familiar with in various forms, from aluminum foil to beverage cans to the framework of cars and bicycles. Aluminum bottles have similar properties to stainless steel bottles, both being metal. One benefit of aluminum is that it is lighter weight than stainless. However, aluminum is less durable than stainless steel and is also a better conductor; thus it transfers heat (cools and heats up) faster. Also, because aluminum suffers from leaching, bottles are coated with a special lining to separate and protect the aluminum from the water. Because of the possibility of breaking this lining through wear or scratching, some attest that stainless steel is "safer" to use than aluminum. Aluminum bottles are also more expensive than their stainless competitors, but some designs do (arguably) look cooler.

Glass

Glass is an amorphous solid composed largely (~75% by mass) of silica (SiO2), along with some other metal oxides such as Na₂O and CaO. Glass has a much longer history than other modern materials as a beverage container. It is superior to metals and plastics in that it does not suffer from any leaching, rusting, or staining problems, and exhibits (in my opinion) the best drinking taste of all beverage materials. Oh, if only I had lived in the era of the glass Coca Cola bottle... *Sigh* Unfortunately, glass has two major flaws: it's heavy and it breaks. So you can forget about glass if you're planning on doing a lot of hiking or travelling, unless of course you feel like lugging the extra weight and don't mind having a razor sharp mess looming in your future. Conveniently, many glass water bottles are now made with silicone/rubber sleeves for added protection and grip, making glass more practical for everyday use.

Conclusion

For the hiker in me, I prefer stainless steel to aluminum or glass for its durability, cost, and chemical "safeness". Besides the weight factor (and let's face it, the water takes up most of the weight anyway), I just don't see much benefit of aluminum over stainless steel, especially considering its higher cost and the factor of the added coating. And while glass bottles are cool, I can't won't use them for hiking, so I don't see the point of owning one on top of the stainless or plastic bottle I already have.

I'm curious to hear your thoughts. Has the water bottle material dilemma ever crossed your mind?

Aluminum Bottle Image

Glass Bottle Image

Stainless Steel Bottle Image