Iron Flask Insulated Review

The Iron Flask Insulated bottle stands out as being the lightest weight metal bottle that we tested, as well as having the lowest cost among top-scoring bottles, although, at first glance, you wouldn't think that this is the budget option. It has a glossy, attractive finish (we tested the Pearl finish) that looks like it belongs in a classy resort spa window. One drawback of that is that they recommend hand washing so you don't diminish the finish. It has three interchangeable lids to easily go between sipping cool liquids through a straw and carrying your coffee to the crag or office with the flip cap. It even has a stainless steel lid if you want to use it as a lightweight backcountry vessel (we tested the 22 oz, but it comes in as much as 64 oz). It is a versatile, attractive, and affordable option for everyday use.

Since we tested this bottle in 2023, there have been no major changes to the bottle except for introducing new colors. We have looked for data on Iron Flask website about whether the bottles contain PFAS (forever chemicals) but have not found any claims that the bottles have or do not have these chemicals. To be fair, few water bottle companies have certified that their bottles do no contain PFAS. This is becoming a more concerning issue for consumers, and we will continue to report on it.

Tested and Rated

GearLab is committed to extensive hands-on testing. We purchased the Iron Flask Insulated, along with more than a dozen other top water bottles. I used the Iron Flask Insulated extensively to fairly rate its performance relative to competing bottles, integrating it into my daily routine and making careful notes about performance, features, and functionality. In the following sections, I will share my experience and thoughts on this bottle.

Performance Comparison

Closure

The Iron Flask comes with three lid options. The stainless steel screw cap and plastic flip cap are the simpler options. I used it mostly as a water bottle with the flip-up straw lid, which I found the most useful for keeping hydrated. The lid is well made, with a silicone gasket to maintain a seal. Whether using the straw to stay hydrated or the flip cap to contain your hot liquids, you can rest assured that this closure won't leak on you.

This bottle performed perfectly on all the leakage tests. In the controlled test, where we left the bottle closed on its side for a day with blue-dyed water inside, the Iron Flask left behind a clean white sheet. In field testing, I didn't notice one instance of this bottle leaking so much as a dribble.

Insulation

The lightweight design of this bottle is no doubt due to thinner materials. It definitely feels lighter and less substantial than the more costly insulated bottles. With a pressured squeeze, there is a give in the walls. Thus, it didn't perform as well as the other insulated bottles in controlled testing. On a practical note, it kept our water cool and hot liquids hot for long enough to be consumed without noticing a detrimental effect of the thinner materials.

In the controlled insulation test, where we left bottles out under the hot sun for 6 hours to see how cool they kept the contents, it was like splitting hairs with most of the insulated contenders. The Iron Flask ended up noticeably warmer, though. The most insulated bottle only reached 73 degrees F (on an 80-degree day), and most other insulated options were in the low to mid-70s. The high temperature of this bottle was 85, which definitely tastes warm. This difference may go unnoticed by folks who use this bottle largely between the home, office, and gym. And it's probably not the best option to keep out under the sun at the work site or garden.

Taste

In this test, we were focused primarily on whether or not the materials impart any chemical flavor to water (say, if it heats up in a hot car). Glass and metal bottles are less likely to leach chemical flavor into your liquids than plastic. And I didn't notice any contamination from the metal vessel. I noticed no chemical taste during testing when sipping cold water through the straw.

I did notice a slight plastic taste during the hot water test. We filled the bottles with 100-degree F water and let them sit before tasting the water to determine if there was leaching. Like most other metal bottles with a plastic straw, this one did have a noticeable taste. I didn't experience chemical flavor when drinking coffee with the flip lid, although the coffee taste does a fine job at covering other flavors. Safe to say that if you use the flip straw lid for its intended purpose, which is cold liquids, then you likely won't experience any tainting of your liquids. And for the record, like in most metal containers, flavors like drink mixes and coffee do linger.

Ergonomics

This bottle has a few factors working for it in terms of its utility and ease of use. It's really lightweight, which makes it easier to carry with the wide carry handle on the lid. The handle also has a convenient carabiner clip, which makes it easy to clip to a strap or carry loop on a pack. I didn't have any issues in terms of convenience toting this bottle around town.

The 22 oz Iron Flask is slender and easy to grip. It fits easily in a cup holder, but if you order the 32, 40, or 64-oz options, just know that they will not. The versatility makes it a good bottle to carry if you want to use it for multiple types of liquid throughout the day. Use your flip cap for coffee in the morning, and then switch to the straw lid to stay hydrated throughout the day.

The bottle is made from 18/8 stainless steel, which is the standard for quality bottles. The difference in the Iron Flask's construction is in the thinness of the material. It's substantially lighter than the more expensive, durable bottles. With a good strong squeeze (of a rock climber's grip), it's easy to produce some give in the sidewalls. We didn't test this out, but we wouldn't bet on this bottle to survive a rock fall or running over without at least some denting (the latter would probably crush it). With this bottle, you're sacrificing durability for a more lightweight design.

The fine, glossy finish makes this bottle very attractive, but it also has some drawbacks. First, it's not dishwasher safe. The manufacturer recommends hand washing to preserve the finish. Second, we were hesitant to take it out on backcountry adventures, or even days on the trail, for fear of scratching or scuffing our fine-looking finish. Although, for the price, you could just buy one to get scuffed at the crag and one to keep nice for the office (unless you want to take your scuffed-up bottle to the office to tell of the harrowing tales of your weekend adventures).

We found the lid to be of quality design and construction, with some unique features that set it apart. The silicone gasket is wide and not inset like many of them, which makes it easier to clean. The receptacle for the straw is made of silicone, whereas all the others we tested were made of hard plastic. This allows the straw to wiggle around while firmly seated and sealed in the lid. We're not exactly sure of the practical use of this feature, but it's a neat design. We already mentioned the carabiner clip on the carry handle, which definitely adds some utility and the design and construction are solid. I could trust that this bottle would stay clipped where I left it. While it's not the toughest bottle in the lineup, we're confident that the Iron Flask will hold up to use. Just don't run it over or drop it off a cliff.

Should You Buy the Iron Flask Insulated?

If you're looking for an insulated bottle to carry between the home, office, and gym, and price is a factor, then you'll love the Iron Flask Insulated bottle. This budget contender makes up for its lessened durability by offering a wide array of color and design options that are sure to bring compliments. The thinner material also results in a lighter-weight design, making it a good option if you want to buy a 32+ oz insulated container for backcountry travel. The standard selection of lids makes it a versatile bottle for use with hot and cold liquids throughout the day. If you're looking for a durable, rugged bottle to hold up to a lot of abuse, then you'll want to check out some of the other bottles designed with this in mind. If you want something lightweight, versatile, suitable for city use, and light on the wallet, then you'll likely love this bottle.

What Other Water Bottle Should You Consider?