About Travel mugs
Travel mugs (introduced in the 1980s)
generally, employ thermal insulation properties for transporting hot or cold liquids.
Similar to a vacuum flask,
a travel mug is usually well-insulated and completely enclosed to prevent spillage or leaking,
but will generally have an opening in the cover through which the contents can be consumed during transportation without spillage.
As the primary mechanism by which hot (not warm) beverages lose heat is evaporation a lid,
even a thin plastic one as used on disposable coffee cups which conducts heat quite quickly,
also serves a vital role in keeping the drink hot.
Mugs with inner and outer walls, but not vacuum treated, are generally called double wall mugs.
stainless steel will be used for the inner wall
while the outer wall can be stainless steel, plastic, or even embedded with other materials.
Mugs designed for use when driving are called auto mugs or commuter mugs.
Travel mugs have a spill-proof lid with a sipping opening and in many cases,
a narrower base, so that they will fit into the cup-holders that are built into many vehicles.
Additional criteria for evaluating auto mugs include:
they must be easy to open single-handedly (to prevent distractions while driving),
include a fill line (to prevent over-filling, which contributes to leaking),
preferably have no handles (no-handled mugs are easier to grab while driving),
should not obstruct a driver's view of the road when he or she is drinking,
and - with regard to cup-holders be able to fit, stably, into a wide range of mug holders
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