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mugs - hydrodynamics and the human mouth

updated sat 25 feb 06


David Hendley on mon 20 feb 06

After 30 years of making mugs and over 50 years of drinking,
I have come to the conclusion that the best functioning mug
or drinking cup must be round and must have sides that are
close to straight and close to vertical. The bottom can be flat
(typical mug) or curved (typical cup), but the body of the pot
cannot introduce any but the most subtle curves.

The diameter of the cup also matters. I can't give a number,
but the diameter of the rim must be right - too small and it is
not comfortable and it hits your nose, too big and the curve
against your lips is not right and liquid wants to spread out
wider than your mouth. This is why any shape that strays too
far from round is less than perfect.

The thickness of the lip is also critical, but more subjective and
maybe a result of what one is used to. To me, an old-time 'diner'
china mug has a lip that is entirely too thick to be comfortable,
and a 'fine china' formal cup is too thin. The 'feel' of the lip on
the mouth also matters, which excludes the use of matt glazes
for many people. They just feel too 'dry' on the lips.

A shape with a 'belly' which is then collared in makes it hard to
drink the last bit of liquid in a cup. When raising it higher to
get that last bit, at a critical point, too much will suddenly come
rushing out. A shape with a 'reverse curve' (nuclear reactor shape)
has the same problem, with the added flaw that a lip that is
substantially flared just does not fit the mouth right.

Of course, you are welcome to make mugs/cups however you
like, and, in fact, to relieve both process and visual boredom,
I sometimes veer from the functional ideal. But the fact remains
that a cylinder is the best functional shape, and if good function
is your goal your working parameters are controlled by the
human mouth and the laws governing the flow of liquids.
It is the challenge of a potter to make interesting and lively
mugs that conform to these narrow parameters.

You can tell just by looking if a mug will function well. At a
friend's this weekend I chose a new cup from his cabinet. A
student mug with a belly, neck, and slightly flared lip. I knew
it wouldn't be functionally ideal, but I still enjoyed using it. It
was well crafted and nicely decorated, and served its function
alright, but it could never become a favorite because of its
less than ideal fit and function.

David Hendley
Old Farmhouse Pottery

Ivor and Olive Lewis on wed 22 feb 06

Dear David Hendley,=20

It was not possible to get an absolute result from the few contributors =
to my survey of the diameter of a mug rim but the plot was stating to =
bifurcate with maxima in the region 70-73 mm and 80-83 mm. This was from =
a sample of about 30 respondents. . As I recall this did not correlate =
with gender.

Point 2. About 15 years ago I attended a Master Class with John Dermer, =
devoted to the design of Functional Domestic Pottery. The Mug was =
treated as a serious subject for consideration. To meet you requirements =
of relating the rim of the mug to the anatomy of the mouth, wall =
thickness should taper as the clay rises to the rim and the diameter at =
the rim should be slightly expanded to create a curved transition that =
will rest on a user's lower lip. That curve is similar to the curve of =
the ball of a persons thumb. This form is almost impossible to make with =
mass produced cast mugs, though it might be possible with those that are =

Among the more important design parameters is that of Fluid Volume. You =
would be hard pushed to find anyone who even thinks about this design =
element. You would need to search hard and long to find out how to build =
a dimensioned design for a measure of beverage served in such a utensil. =
Relating height, diameter and wall thickness to contained volume is not =
addressed in any of the texts about Ceramic design that I have read. =
Mick Casson and Robin Hopper tell you what amount of clay to use, but =
not how to calculate the mass for a specific volume of beverage. So we =
accept that the average mug will need about an average three quarter =
pound ball of clay. Why bother to make it harder for Ceramic Students?

Best regards,

Ivor Lewis.
South Australia.

Ann Brink on wed 22 feb 06

Ivor wrote:
"Among the more important design parameters is that of Fluid Volume. You
would be hard pushed to find anyone who even thinks about this design
element. "

My comment is not about the volume, but about the shape of the fluid when a
cylinder is altered to be off round. It only becomes apparent if the fluid
is a contrasting color from the interior of the cup. This has just hit me
lately, as I've been drinking tea from a cup (tumbler, actually) that had
quick vertical grooves made with 2 fingers inside and one outside just after
throwing. Since the wheel was moving slowly, the grooves are at an angle,
and when I look into my cup, the tea is star-shaped. I never tire of seeing

Ann Brink in Lompoc CA

Lee Love on fri 24 feb 06

The basic cup and bowl in Japan was traditionally sized to the size of the
hand. For example: to get the size of a ricebowl, made a circle by
joining the thumb tips and tips of the middle fingers of both hands. (mt
diameter measure is 13cms. Which is the same as the famous Korean Yi

Lee Love
in Mashiko, Japan My Photo Logs

"Where the spirit does not work with the hand, there is no art."
--Leonardo da Vinci