B Why does coffee in a glass leaves its signatory on the surface?

AI Thread Summary
The discussion revolves around the phenomenon of liquid rings forming under cups, particularly coffee mugs. Participants explore how these rings can result from spilled liquid, condensation from cold drinks, or residual water left in washed mugs. The conversation suggests that both external dribbles and internal condensation contribute to the formation of these rings. Additionally, there is speculation about whether moisture from the surface beneath the cup could also play a role. Overall, the topic highlights the various factors that can lead to the appearance of fluid circles under drinking vessels.
Zohar
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How does hot fluid comes down to the surface of the glass it's in?
Some of us may use coffee coaster for our drinks. I was always wondering about that phenomenon and failed to find something on the net yet.
 
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Zohar said:
Summary:: How does hot fluid comes down to the surface of the glass it's in?

Some of us may use coffee coaster for our drinks. I was always wondering about that phenomenon and failed to find something on the net yet.
Can you please restate the question, I am struggling to understand what you are referring to
 
Haven't you seen a circle of fluid under a cup of coffee? How does it happen?
 
Zohar said:
Haven't you seen a circle of fluid under a cup of coffee? How does it happen?

ohh ok, that's what you are referring to ...

Because the coffee has been spilt/dribbled down the side of the cup ... simple as that
 
Zohar said:
How does it happen?

it will happen on any cup, drinking glass, bottle of any liquid
and it will happen in a different way if the liquid is cold and it produces condensation
that then runs down the side of the container to the base. This is in addition to any
liquid that rund down the outside surface of the cup etc from what is dribbled/spilt
during the drinking process
 
Zohar said:
a circle of fluid under a cup of coffee?
I wonder if you leave your mugs on the side of the sink after washing them up. A small amount of water can stay in the inverted bottom and that can turn up on the table top. Experiment to find if drying up the mug totally will solve the problem. I can't think of any other reason.

Except if there is water in the wood(?) surface which is brought to the surface by the hot mug and then condenses round the cooler periphery to form a ring. Or is the ring in fact due to water and not just a temporary effect of heat on the varnish?

This is a Sherlock Holmes problem.
 
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