Are Thermos Travel Mugs Dishwasher Safe?

Thermos travel mugs were originally intended for hikers and campers traveling deep into the woods or just camping beside a quiet stream with the family. They were designed to be cleaned using whatever water source was available, often without soap. Nowadays, they are used by Mums taking their kids to school, office workers, emergency services, and everyone in-between. Is it then safe to just pop them in the dishwasher?

Thermos travel mugs are not dishwasher safe. The materials used in producing these mugs are not designed to withstand the extreme heat generated by a dishwasher. Clean the mug by hand with a soft cloth and a gentle detergent. No cleaning agents that are abrasive or contain chlorine or bleach.

Like ‘Hoover’ for vacuum-cleaners, ‘Jacuzzi’ and ‘Kleenex’ for their respective products, the word ‘thermos’ is now synonymous with vacuum pots and cups worldwide. It is sometimes impossible to know if someone refers to the registered company, Thermos, or its myriad of generic wannabees. (thermos; un-capitalized)

Are Thermos Travel Mugs Dishwasher Safe?

According to the official Thermos Website, most (not all) of their products are top-rack dishwasher safe, but they still recommend washing by hand to keep the beautiful finish looking great.

Care and Use: Specifically for Stainless Steel Vacuum ware (incl travel mugs)

Take care of the item, and you can expect years of dependable service. They ask that you read the guidelines below to get the most out of your Thermos travel mug.

  • Wash and rinse the mug thoroughly before the first use and after each use. Handwashing the item is highly recommended.
  • DO NOT use an abrasive cleaner or an abrasive sponge on the mug. These may dull the finish.
  • DO NOT use regular bleach or another cleaner containing chlorine or bleach on your mug.
  • Before each use, pre-heat/chill the travel mug for best insulation efficiency. Fill the mug with hot/cold water and attach the lid, allowing ten or more minutes to pass before emptying. After filling with desired liquid, place the lid on your mug to increase thermal efficiency, both hot and cold.
  • DO NOT place your travel mug in the dishwasher to clean. It is not dishwasher safe (except stainless steel bottle/can-insulators).

Why Not Wash Your Thermos Travel Mug In A Dishwasher?

The extreme heat may play havoc with your non-stainless steel (or glass) components, and rubber or plastic seals will perish or distort, rendering the unit no longer airtight. This leads to leaking and, far more importantly, the end of your mug’s vacuum capabilities and ability to hold temperatures constant for long periods.

Is Thermos a Registered Brand Name?

The word thermos is a genericized trademark used sometimes, since the early 20th century, as a term for any vacuum-insulated flask regardless of manufacturer. However, the trademark THERMOS is registered in over 115 countries worldwide. Their headquarters is located in Schaumburg, IL. USA.

Are Generic thermos Flasks And Travel Mugs Dishwasher Safe?

Since most of the generic range of travel mugs is produced in China, it is not always possible to find compelling data on the materials and safety concerns involved. Still, independent tests on random units are conclusive. Other than the stainless steel bottle and lid, the materials tested are, like the original Thermos products, not dishwasher safe and should be washed by hand.

Who Invented The Thermos?

James Dewar invented the thermos flask way back in 1892, in the course of doing cryogenic research. Like most great inventions, it was created almost by accident. His research had nothing to do with millions of people filling up a flask or mug daily with everything from coffee, soup, and hot water to Frappuccino.

The thermos was patented in 1904 and renamed for industrial use by the Thermos company, which was created by two German glassblowers who recognized its potential to keep liquids warm or cool. The name ‘thermos’ was created by a Munich resident after a competition was held in Germany to name this exciting new product. The name is derived from the Greek ‘therme,’ meaning hot or heat.

Where Are Thermos Products Made?

Thermos® has manufacturing facilities in the USA, China, and Malaysia, and Research & Development facilities are based in these plants and in Japan. All Thermos products are manufactured under strict quality control to meet the exacting standards of the many countries supplied by Thermos.

Most of their plastic bottles are manufactured in Batesville, MS., and although several other countries are involved, the bulk of their stainless steel lids and bottles are manufactured in China.

What Material Is Used To Regulate Temperature In A Thermos Mug?

A glass bottle was used from 1911 when the British Trademark holders bought part of the trademark from the German owners and developed the inner bottle for household use. In 1978, Nippon Sanso K.K. of Tokyo, Japan, developed a stainless steel vacuum bottle which they incorporated into Thermos products when they acquired the Thermos operating companies in the U.S., U.K, Canada, and Australia, in 1989.

Why Did They Stop Making Glass Thermos?

Glass vacuum bottles aren’t as commonly made anymore because they are fragile and stainless steel has replaced glass as the material for vacuum bottles. However, some glass thermos sizes are still available as replacements if you know where to look.

My own experiences are that glass is far superior to stainless steel in a vacuum flask, where longevity of temperature is critical, though of less importance in a travel mug, where the contents are generally consumed far sooner. Stainless steel may be preferable as the material of choice in a travel mug, which is banged and dropped a lot more than a flask.


Since dishwashers reach incredible temperatures, it may be wise to err on the side of caution and wash all Thermos (or thermos) products by hand, rather than risk the loss of a favored item. If your hands can withstand the heat, it’s fine for your Thermos travel mug, but don’t immerse in water any hotter, and avoid harsh cleaning agents.


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