​Today we're exploring the question, will a dent affect your bottles insulation?  Unless you have Spiderman-like reflexes, inevitably you will drop your bottle.  Plastic bottles like Nalgenes will be fine, but dual-wall stainless steel bottles are a different story.  Steel is a very strong and durable material for water bottle construction, but one major downside is that it is prone to denting.

​Many of these water bottles are not exactly cheap, costing as much as $50 for larger bottles from brands like YETI and Hydro Flask.  So if you've invested in a brand you love, you want to know that your insulation still works, right?

​The truth is that dents CAN affect your bottle's insulation, but it's not as simple of a question to answer as it may seem at first.  The location and size of the dent play a role, so there are more things to consdier than you might expect.

So today we're exporing the question, "which dents affect your bottle's insulation?"

Coming Next:

• Reviewing why insulated bottles work
• Cutting open bottles (for science!)
• Insulation tests after dropping a bottle from greater and greater heights

I recently posted two videos about this test.  One that's a 3-minute recap of the most important details, and another that's a full-length 18-minute video showing more of the testing footage and general information about these types of bottles.  They each cover similar info as this post, so check those out if you'd prefer to watch the recap!

From cutting open these two bottles, ​I found that the spacing between the two layers is much wider on the bottom compared to the sides.  So your bottle can have bigger dents on the bottom and still hold its insulation, which is probably by design because the bottom is the most likely place to get a dent.  But if you are unlucky enough to drop your bottle on its side onto a rock or something else that dents it there, then the dent doesn't need to be as deep to create a contact point between the two layers.

It's not just the location of the dent, but also the severity that matters.

Smaller isolated dents can create contact point between the two steel layers.  Any contact point like this is going to be a pathway for heat transfer through conduction, so these dents can affect your insulation.  But the good news is that your bottle will still have good insulation around the majority of it, so it won't be a complete failure.

Worst-case, you might get a larger dent that cuts through the outer layer of steel. This allows air to enter the space between the steel layers to replace the vaccum, and then your bottle will be not better at insulating than a single-wall bottle.

​Next, I stress tested a RevoMax bottle by dropping it from increasing heights.  I did a 4 hour insulation test before the test and after each drop.

The bottle took A LOT of damage before the insulation was effected, even including some dents with extreme buckling and folding of the steel.

The bottle still had the same insulation after 12", 24", 36", and 48" drops.

Eventually the insulation was completely compromised (Failure B mentioned above) after the 60" drop.  This occurred when multiple dents with severe buckling overlapped, and that overlapping area is where there was too much repeated strain on the steel to the point that it cut through the outer layer.

So the main reason the insulation failed is because the compound dents overlapped.  I wouldn't be surprised if the bottle would have held insulation after a single 60" drop.

In the vast majority of cases, YES!

​​The bottom line is that you probably don't need to worry about your bottle's insulation being compromised by a dent.  Most dents, even really severe ones, are not large enough to affect the insulation.  Plus, the vast majority of people will replace their bottle before the insulation is affected because large dents can make the bottle sit wobbly, which is pretty annoying.

​But if you like to hang onto your bottles longer than the average person and you start to get overlapping major dents, that's when you would be more likely to start seeing your insulation get worse or potentially even competely fail.

​But if you have any doubts, do an insulation test.  Fill your bottle with the hottest water from your sink, measure the temperature, then let it sit for about 4 hours and measure it again.  If the temperature dropped less than ~10 degrees F, your insulation is still probably good.  More than ~10 degF and you might have a problem.

Other than never dropping your bottle EVER, there plenty of effective, easy options to keep your bottle protected and insulation as-designed.  Here are a few to consider:

• Nuovo Adjustable Carrying Pouch
• BottlePro's Neoprene Sling: https://amzn.to/3TMVrLF
• Hydro Flask Bottle Boot: https://amzn.to/43ynstN
• Hydro Flask Bottle Carrier: https://amzn.to/4ctTlHI​

You’ve probably heard about dual-wall insulated bottles, but what about triple-wall?  If two walls are good, then three are better, right?  Let’s find out.

Dual-wall stainless-steel bottles have been around for a long time, and brands like Hydro Flask and YETI really launched them into mainstream use within the last decade.  Each bottle has two walls of stainless steel with a vacuum in between, and the lack of air reduces how much heat can transfer in or out.  We tested quite a few of these bottles for a video earlier this year, and that turned into one of our best-performing posts.
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Triple wall bottles are not as widespread, but there are a few brands out there marketing this type of design, including S’well, RevoMax, EcoVessel, and Owala.  We didn’t discuss this type of bottle as we would have liked in our previous insulation test video, so we thought now would be a good time to revisit it, this time with a focus on seeing if the triple-wall design is worth the marketing hype.

Before we get started, there are a few details to point out.

1. Hot vs Cold: In our previous video, we weighed ice before and after to determine how much of it had melted.  This time, we’re doing a hot-water test and using a thermometer to measure temperature.  We changed this up to try to make the test more reliable, and because insulation is the resistance to temperature change in either direction, it doesn’t matter if we’re testing hot or cold.  We should still get the same relative results and rankings for each bottle.
   
2. Bottle and Mouth Size: Most of the bottles we tested hold 32 ounces, but we have a few other bottles that we wanted to test too.  We also had a couple of bottles that are narrow mouth instead of wide mouth.  For an ideal test, all of the bottles would have the same volume and the same mouth opening diameter. We’re a small channel that can only afford to buy so many bottles, so we’re working with what we have.  That being said, our results will still give you a pretty good idea of what to expect, especially if you’re looking for a 32-ounce size.
   
3. Lid Design: Different lids have different insulating properties.  Because our primary goal is to test the insulation differences between dual and triple walls, we wanted to remove the variable of the lid design from our test.  More on this later.
   
4. Triple-Wall vs Triple-Layer: finally, the term “triple-wall” is a bit misleading.  We’re going to spend a couple minutes geeking out about thermodynamics to explain how it works, so skip ahead if you’re like to move straight to the test.

Many people assume triple-wall means three walls of stainless-steel, but that’s not correct.  If you look closely at the marketing and listings, you’ll notice that it probably says “triple-layer” instead of “triple-wall.”  It’s a small but significant distinction because they don’t really have three walls.  They have the same dual wall construction with a vacuum in between, and the third layer refers to a copper coating on one of the stainless-steel walls.

From S'well's website:
“Thanks to our Therma-S'well® Technology and triple-layered insulation, which includes a copper layer, S'well products are able to keep any liquid hot or cold for long stretches, while maintaining a condensation-free exterior.”

Emissivity is a material property that indicates how efficiently heat is transferred by radiation.  A material with a lower emissivity value will transfer less radiant heat compared to a material with a higher value.  Copper has an emissivity of 0.05, so while the copper coating won’t do much to prevent heat conduction, it will help prevent heat radiation.  For reference, stainless-steel has a higher emissivity of 0.59, so the steel won’t prevent radiation heat loss as efficiently by itself.

We looked at 14 total bottles.  11 bottles are dual-wall, and 3 have triple-layer insulation with the copper coating.

Dual-Wall:

• Klean Kanteen 32-ounce TKWide Insulated
  
• Hydro Flask 32-ounce Flex Straw
  
• Hydro Flask 32-ounce Trail Series (lighter)
  
• Takeya Actives 32-ounce (includes Matching Bottle Boot)
  
• Camelbak Chute Mag 32-ounce
  
• Ozark Trail 32-ounce
  
• Steepware 22-ounce Tea Tumbler
  
• FJbottle 34oz
  
• YETI 36-oounce Chug Cap
  
• Iron Flask 40-ounce
  
• Stanley Quencher 40-ounce
  

Triple-Layer:

• RevoMax 32oz
  
• EcoVessel Boulder Series 32-ounce
  
• S’well 25oz (the narrow mouth from this video)
  

We were originally going to boil water to recreate steeping tea or brewing coffee, but it would have taken quite a few batches and taken a lot longer.  So instead, we filled up each bottle with the hottest water from our sink.

As mentioned before, different lids have different insulating properties.  Because our main goal was to compare the triple-layer vs dual-wall insulation, we wanted to keep the different lid styles from impacting the results as much as possible.  We purchased a sheet of Styrofoam insulation, cut it into a bunch of smaller pieces, and pressed them onto the rim of the bottles.  This created an impression in the Styrofoam pieces that helped limit the potential for gaps and temperature loss.​

We poked a hole through each piece of foam with our thermometer, and we used a few other smaller pieces of insulation to cover up the holes when we weren’t taking measurements. ​

We measured the temperature every hour for the next four hours, again around hour 8, and one more time around hour 20.  With each measurement, we inserted the thermometer through the hole in the Styrofoam cap until the temperature equalized.
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This chart and graph show the percentage temperature change at different times during our test, which lasted 19 hours and 31 minutes.  Temperature drops ranged between 17.2% on the low end to 27.0% on the high end.  Looking closer at the data, there are a few interesting results to note.

Two of the triple-layer bottles, RevoMax and S’well, had the best results.  The third triple-layer bottle, EcoVessel, didn’t fare as well, but it was still in the top five.

The best dual-wall bottle really surprised us.  Ozark Trail, the Walmart brand bottle that we bought for $11, had an 18.5% temperature loss.  Compare that to 20.9% for a $50 YETI Rambler and 24.2% for a $45 Hydro Flask.
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The worst bottle by a wide margin is Steepware, which is a bit ironic given that it’s primarily made for brewing tea.  That being said, it’s probably not a major concern because most people will drink the tea within a few hours before it goes stale.

So based on the results, it does appear that the copper layer may have an impact and helps insulation.  However, depending on which brands you’re comparing, the difference between triple layer and dual wall insulation might not be as great as you would have thought.  When you average the percent temperature loss for dual wall vs triple layer bottles, you get 22.7% and 18.3% respectively.  A 5% difference over 20 hours is significant, but it’s not really game-changing in our opinion.

However, there’s another big variable that makes this conclusion a bit uncertain.  We can’t afford to buy every type of bottle, and it just so happens with our bottle collection that the two best performing bottles were also our only two narrow mouth bottles.  Because most heat is lost through the lid and mouth opening, narrow mouth bottles should have an advantage over wide mouth ones.  We’d like to do another test in the future that focuses on wide-mouth vs narrow-mouth insulation once we have more narrow mouth bottles to compare.

But let’s face it, you’re not going to be walking around with one of these bottles with a Styrofoam cap.  We did the test first because we wanted to isolate the effect that the copper layer has on the insulation, but the more practical test that you can use compares the bottles when using the lids that they come with.  So we ran a 2nd version of the test using the bottle lids.

For each measurement, we swapped the bottle lid with the Styrofoam piece from the previous test.  Then we pushed the thermometer through the Styrofoam, and this prevented excessive temperature loss for the 15-20 seconds that we needed for each measurement.  Once we had the reading, we put the normal cap back on.

​This test lasted for 19 hours and 17 minutes, and we made the same type of chart and table to show the results.  Right away, there are some interesting data points and details to unpack.

The relative rankings were mostly the same as with Test A, but there was a much wider range of results with a 13.5% temperature drop on the low end to 30.1% on the high end.  That’s an increase in the range of results from 9.8% with Test A to 16.6% with Test B.

The same two brands performed the best (RevoMax and S'well), but they widened their lead significantly.  However, keep in mind that these are the only two narrow-mouth bottles in our test.

Ozark Trail had a great showing again, and this was the best dual-wall bottle in both tests.
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Unfortunately for Steepware, this bottle was even more of an outlier on the wrong side of the average compared to Test A.

​While the relative rankings were similar for both tests, you may have noticed the rankings did change in some cases.  For example, Hydro Flask’s Trail Series jumped from the 2nd worst with Test A to the middle of the pack with Test B.  Since the only change between the two tests was that we switched from the standardized foam pieces to each brand’s lid, any changes in the rankings means that some brands have designed lids with better insulation than others.

Standardizing the Results
Tests A and B had slightly different total durations, so to better illustrate how the results for each bottle changed between the tests, we needed to standardize the results.  We calculated the temperature drop per minute over the duration of both tests, then we multiplied that by 1200 to simulate a 20-hour test.  Then we compared Test A vs Test B for each brand, and this graph shows how each brand changed.

​Bottles that fall on the left side had better results with their brand’s lids instead of the Styrofoam cap, and bottles on the right did better with the Styrofoam.  

​S’well, RevoMax, and both Hydro Flasks were the only bottles that improved with Test B.  When you look at the lids with each of these bottles, you can see that they seem to have more built-in insulation, like with S'well and RevoMax.

Most of the other bottle lids like Steepware and Takeya don’t have built-in insulation and just have single layer plastic construction in the cap, so it’s understandable that they didn’t fare as well. ​

​So when we take a step back and look at the results as a whole, we have a few main takeaways.

1. Triple-Layer vs Dual-Wall: Triple-layer construction does seem to help compared to dual-wall insulation, but it may not be as big of a difference-maker on its own as the marketing might make you think.
   
2. Lid Design and Narrow vs Wide Mouth: The more significant factor appears to be narrow vs wide mouth and the insulating properties of each brand’s lid design.
   
3. Price: Price doesn’t guarantee results, as Ozark’s $11 bottle did better than all the other dual-wall bottles, including YETI and Hydro Flask.

​Based on these results, we have a few more video ideas that we may work on in the near future.  Once we have more narrow-mouth bottles in our collection, we want to compare those against wide-mouth bottles.  We also think it would be interesting to focus on premium brands vs budget brands, because let’s face it, we’re probably not the only ones that were surprised that Ozark Trail outperformed YETI.  And finally, we only ran one instance of each test, and for more reliable comparisons and data, we ideally would repeat the test more times and average the results.