Glass Thermos vs Stainless Steel

Couple carrying stainless steel water bottles

Reusable water bottles can have various linings or walls, including glass and stainless steel. Since there are pros and cons to each material, we're exploring the science behind glass thermos vs stainless steel, along with their similarities and differences.

Glass Thermos vs Stainless Steel: General Overview

Plastic bottles have a low recycling rate and short life cycles. While they are relatively cheaper to produce, glass thermos and stainless steel bottles are more sustainable, functional, and safe to use.

Man carrying a Hydro Cell stainless steel bottle

Glass Thermos

A glass-lined thermos is a vacuum flask with an inner and outer glass lining, mostly created from borosilicate glass. Some versions contain stainless steel exterior walls as reinforcements, while others use double-walled glass.

From the late 1890s to the early 1910s, glass became a standard for lunch boxes and storing liquids. Challenges in using glass paired with modern innovations changed the industry of glass thermos.

Stainless Steel

Culinary-grade stainless steel linings served as the solution to the challenges of using glass thermos. Stainless steel is a corrosion-resistant alloy of chromium, iron, nickel, and other metals.

Compared to other materials, stainless steel boasts strong mechanical properties even at ambient temperatures. Its elasticity and ductility enable it to withstand metal forming processes and resist heavy wear.

Glass Thermos vs Stainless Steel

Knowing the similarities and differences between glass thermos and stainless steel gives you a better understanding of their properties. With this knowledge, you can determine which material would suit your needs the most.

Similarities Between Glass Thermos and Stainless Steel

Since the mass production of plastic 60 years ago, it has produced 8.3 billion metric tons of products, with 6.3 billion metric tons ending up as garbage. Over the years, glass and stainless steel became reliable alternatives because of their similarities in some aspects.


It's more encouraging to take regular sips throughout the day when there's water near you. Whether using a glass thermos or a stainless steel bottle, it's much easier to drink water when the container is within arm's reach.

In effect, it's also more convenient to track your fluid intake rather than getting up while you're busy working and then grabbing a glass of water.

Free From Toxin Leaching

Hydro Cell water bottles, for instance, mainly consist of 18/8 stainless steel, which is a food-grade material that resists corrosion and toxin leaching. Meanwhile, glass is also generally food-safe.

Couple carrying stainless steel water bottles
  • Stainless steel and glass are both chemical-free, which means they don't contain Bisphenol A, a chemical used for producing plastics and resins.
  • Unlike plastic bottles, you can reuse glass thermos and stainless steel tumblers without risking exposure to polyethylene terephthalate. Even when you pour hot drinks, there won't be PETE chemicals that would break down and leach carcinogenic, hormone-disrupting phthalates to your stainless steel or glass bottle.
  • Glass and stainless steel don't contain polystyrene, which can break down and leach into food and drinks, particularly when exposed to heat. This human carcinogen is a common material in foam containers.

Eco-Friendly Design

Single-use plastic bottles have a detrimental effect on the environment, animals, and human health. In contrast, stainless steel and glass thermos are more considerate to the environment.

  • Stainless steel is among the world's most recyclable elements. It has a 100% recyclability rate because it is easier to spate with other materials. Similarly, the long-lasting nature of glass makes it recyclable to become a raw material again.
  • Unlike frail plastic bottles, there are many ecological benefits to using reusable water bottles, whether in the form of a glass thermos or stainless steel tumbler.
  • Most glass thermos and stainless steel water bottles come with sleek designs, a myriad of colors, and many functional accessories that you can't get on plastic bottles.

Differences Between Glass Thermos and Stainless Steel

Comparing the differences between stainless steel and glass thermos also helps you better understand their qualities.

Thermal Conductivity and Heat Retention Properties

Glass and stainless steel are materials used as lining for water bottles. As an inner lining, they can retain the temperature of the beverage inside, whether it's hot or cold.

However, glass has a lower thermal conductivity rate than stainless steel, making it slower for heat to move. By this logic, glass has better heat retention than stainless steel.

  • Hydro Cell drinking bottles use stainless steel as the main component. There's still a vacuum sealing surrounding the stainless steel, preventing quick heat transfer. As a result, a Hydro Cell stainless bottle can keep hot beverages hot for 12 hours.
  • In the case of glass thermos, prolonged heat retention depends on whether there's an additional metal or double-glass wall.
  • Stainless steel or glass can serve as exterior walls to prevent condensation. While this is automatic for high-grade stainless steel bottles, the lack of condensation is only possible for double-walled glass tumblers.


Proper maintenance can prolong the lifespan of a drinking bottle, whether it's a stainless steel bottle or glass thermos. Despite that, glass drinkware has a higher chance of breaking than stainless steel.Woman carrying a Hydro Cell water bottle

  • Glass vessels often come with a metal base coated in aluminum or plastic to protect them from pressure. However, they may still suffer from scratches, chips, and cracks, ultimately leading to shattering.
  • Depending on the composition, glass can be strong or brittle. As a vacuum creates inward pressure, the glass may shatter and leave shards of glass in the bottle. There may still be unforeseen circumstances where physical force or long-term wear and tear can break the glass.
  • In contrast, stainless steel water bottles are more resistant to corrosion since it's basically composed of metal.
  • There are many ways to repurpose a stainless steel bottle because of its durable material. You can even put it in the freezer to store food. However, you can't do this with a glass thermos because ice cubes may damage the inner liner.

Effect on Taste

Stainless steel may suffer from oxidization in the long run. If you don't know how to clean a stainless steel bottle properly, tarnish or mold may grow, affecting the taste of your beverage.

On the other hand, a glass thermos has little to no effect on flavor because there's no chemical or physical reaction when water comes in contact with the glass.

Some people taste a metallic flavor when drinking on a stainless steel tumbler, especially brand new ones. You can eventually remove such taste as long as you frequently wash and disinfect it.

Major Distinguishing Factor

Stainless steel has better insulation and impact resistance than glass because its alloy elements improve hardenability and strength. While a glass thermos has greater heat retention properties, it is often more fragile and prone to damage.

When to Use Glass Thermos?

It would be better to use a glass thermos if you want to prevent having a metallic taste in your water. It's also easier to remove the flavor and odor of infused herbs and fruits in a glass thermos. However, this shouldn't be an issue if you’re using Hydro Cell bottles.

When to Use Stainless Steel?

If you want excellent insulation, use a stainless steel water bottle, especially vacuum-sealed ones like Hydro Cell. It's also a good option if you want a budget-friendly yet more durable drinking bottle. Moreover, a stainless steel bottle is more convenient for bringing water outdoors.

The Verdict

Both glass thermos and stainless steel drinking bottles can help you monitor water intake and ensure hydration. A glass thermos is ideal for long heat retention, whereas stainless steel is better suited for practicality and durability. However, the final choice should still depend on your budget and needs. 

You may also like