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## what makes some teapots dribble ?

### ivor and olive lewis on tue 29 nov 11

My teapots must be in the prime of life . I cannot recall ever having =3D
made a teapot that suffered from this affliction.
I have See Robin Hopper, "Functional Pottery." Fig 9.'30. p 147, ed 1986 =
=3D
Quote, "Vent hole in lid helps by creating a passage of air which pushes =
=3D
the liquid out.". My apology to Mel.
I'm still working on the physics of this issue.
Best regards,
Ivor
Subject: What makes some teapots dribble ?

Hello Ivor, this really gave me a chuckle: "Which leaves the question =3D
hanging. What makes some teapots dribble?" When I think of humans, which =
=3D
ones do the dribbling? I think it is mostly the very young and the very =3D
old. So these teapots must either be very young or very old QED!
That Xmas cake sounds delicious.

Kind regards from
Fay, and Ralph Loewenthal

### paul gerhold on tue 29 nov 11

Ivor
The driving force for the flow is gravity. The vent hole does not create a
passage of air that pushes the liquid out. At the very best if you had a
sealed teapot with a very tiny spout opening the vent hole might serve to
allow the air pressure inside and outside the pot to equalize negating any
effect whatsoever due to air pressure.

The physics of why some teapots pour well and others do not can be found in
the study of fluid mechanics. Turbulence due to clay roughness and
smoothness of the spout inside would be one contributor along with spout
length (friction) and the design of the intersection between the spout and
the body of the pot.

Also important will be the amount of friction generated at the point where
the tea leaves contact with the spout. You could look at dividing the
force vector from initial flow of the tea into horizontal and vertical
vectors. The larger the horizontal and the smaller the vertical the more
likely the tea will be not to drip down the spout.

So basically what you want for a teapot to pour well is good velocity of
the tea, low friction at the spout, and maximum horizontal component of
the velocity.

Paul

On Mon, Nov 28, 2011 at 11:57 PM, ivor and olive lewis <
iandol@westnet.com.au> wrote:

> My teapots must be in the prime of life . I cannot recall ever having mad=
e
> a teapot that suffered from this affliction.
> I have See Robin Hopper, "Functional Pottery." Fig 9.'30. p 147, ed 1986
> Quote, "Vent hole in lid helps by creating a passage of air which pushes
> the liquid out.". My apology to Mel.
> I'm still working on the physics of this issue.
> Best regards,
> Ivor
> Subject: What makes some teapots dribble ?
>
>
> Hello Ivor, this really gave me a chuckle: "Which leaves the question
> hanging. What makes some teapots dribble?" When I think of humans, which
> ones do the dribbling? I think it is mostly the very young and the very
> old. So these teapots must either be very young or very old QED!
> That Xmas cake sounds delicious.
>
> Kind regards from
> Fay, and Ralph Loewenthal
>

### John McClure on tue 29 nov 11

I think is better understood if you think of it in the terms of gravity suc=
=3D
ks the tea out.=3DA0 It is interesting to see the community discuss Newtoni=
an=3D
physics.=3DA0 Add to your thinking the question, if the vent hole allows a=
ir=3D
to push the tea out, why doesn't the tea get pushed out of the spout whene=
=3D
ver the bottom of the spout is covered? The vent hole allows equal pressure=
=3D
to be on both sides of the tea column and lets gravity=3DA0 do it's wonder=
s.=3D
=3D0A=3D0A=3D0AAlso, even Robin can make an error in physics=3D0A;o)=3D0AJ=
ohn McClur=3D
e=3D0A=3D0A________________________________=3D0A From: ivor and olive lewis=
ol@WESTNET.COM.AU>=3D0ATo: Clayart@LSV.CERAMICS.ORG =3D0ASent: Monday, Nove=
mber=3D
28, 2011 11:57 PM=3D0ASubject: Re: What makes some teapots dribble ?=3D0A =
=3D0AM=3D
y teapots must be in the prime of life . I cannot recall ever having made a=
=3D
teapot that suffered from this affliction.=3D0AI have See Robin Hopper, "F=
un=3D
ctional Pottery." Fig 9.'30. p 147, ed 1986 Quote, "Vent hole in lid helps =
=3D
by creating a passage of air which pushes the liquid out.". My apology to M=
=3D
el.=3D0AI'm still working on the physics of this issue.=3D0ABest regards,=
=3D0AIvo=3D
r=3D0A=3DA0 Subject: What makes some teapots dribble ?=3D0A=3D0A=3D0A=3DA0 =
Hello Ivor, =3D
this really gave me a chuckle: "Which leaves the question hanging. What mak=
=3D
es some teapots dribble?" When I think of humans, which ones do the dribbli=
=3D
ng? I think it is mostly the very young and the very old. So these teapots =
=3D
must either be very young or very old QED!=3D0A=3DA0 That Xmas cake sounds =
deli=3D
cious.=3D0A=3D0A=3DA0 Kind regards from=3D0A=3DA0 Fay, and Ralph Loewenthal

### May Luk on tue 29 nov 11

In trying to understand what exactly is a dribbled teapot and I ran

http://www.gizmag.com/stop-teapots-dribbling/13199/

http://www.telegraph.co.uk/science/science-news/6454568/How-to-stop-a-teapo=
=3D
t-dribbling.html

Thanks for the physics reminder, Paul. My last physics lesson was 32
years ago and I don't remember vector head and tail!

Best Regards
May

On Tue, Nov 29, 2011 at 9:34 AM, paul gerhold wr=
=3D
ote:
> Ivor
> The driving force for the flow is gravity. =3DA0The vent hole does not cr=
ea=3D
te a
> passage of air that pushes the liquid out. =3DA0At the very best if you h=
a
> sealed teapot with a very tiny spout opening the vent hole might serve to
> allow the air pressure inside and outside the pot to equalize negating an=
=3D
y
> effect whatsoever due to air pressure.
>
> The physics of why some teapots pour well and others do not can be found =
=3D
in
> the study of fluid mechanics. =3DA0Turbulence due to clay roughness and
> smoothness of the spout inside would be one contributor along with spout
> length (friction) and the design of the intersection between the spout an=
=3D
d
> the body of the pot.
>
> Also important will be the amount of friction generated at the point wher=
=3D
e
> the tea leaves contact with the spout. =3DA0You could look at dividing th=
e
> force vector from initial flow of the tea into horizontal and vertical
> vectors. =3DA0The larger the horizontal and the smaller the vertical the =
mo=3D
re
> likely the tea will be not to drip down the spout.
>
> So basically what you want for a teapot to pour well is good velocity of
> the tea, low friction at the spout, =3DA0and maximum horizontal component=
o=3D
f
> the velocity.
>
> Paul
>
> On Mon, Nov 28, 2011 at 11:57 PM, ivor and olive lewis <
> iandol@westnet.com.au> wrote:
>
>> My teapots must be in the prime of life . I cannot recall ever having ma=
=3D
de
>> a teapot that suffered from this affliction.
>> I have See Robin Hopper, "Functional Pottery." Fig 9.'30. p 147, ed 1986
>> Quote, "Vent hole in lid helps by creating a passage of air which pushes
>> the liquid out.". My apology to Mel.
>> I'm still working on the physics of this issue.
>> Best regards,
>> Ivor
>> =3DA0Subject: What makes some teapots dribble ?
>>
>>
>> =3DA0Hello Ivor, this really gave me a chuckle: "Which leaves the questi=
on
>> hanging. What makes some teapots dribble?" When I think of humans, which
>> ones do the dribbling? I think it is mostly the very young and the very
>> old. So these teapots must either be very young or very old QED!
>> =3DA0That Xmas cake sounds delicious.
>>
>> =3DA0Kind regards from
>> =3DA0Fay, and Ralph Loewenthal
>>

--=3D20
http://www.artspan.org/artist/mayluk
http://www.ceramicsbrooklyn.com/

### ivor and olive lewis on wed 30 nov 11

Dear Paul,
Thank you for joining the discussion.
You confirm what I have said, that Gravity provides the motive force to =3D
the fluid and that it is not air pressure that causes it to flow.
Ivor Lewis,
REDHILL,
South Australia.

----- Original Message -----=3D20
From: paul gerhold=3D20
To: ivor and olive lewis=3D20
Cc: Clayart@lsv.ceramics.org=3D20
Sent: Wednesday, November 30, 2011 1:04 AM
Subject: Re: What makes some teapots dribble ?

Ivor
The driving force for the flow is gravity. The vent hole does not =3D
create a passage of air that pushes the liquid out. At the very best if =
=3D
you had a sealed teapot with a very tiny spout opening the vent hole =3D
might serve to allow the air pressure inside and outside the pot to =3D
equalize negating any effect whatsoever due to air pressure.

The physics of why some teapots pour well and others do not can be =3D
found in the study of fluid mechanics. Turbulence due to clay roughness =
=3D
and smoothness of the spout inside would be one contributor along with =3D
spout length (friction) and the design of the intersection between the =3D
spout and the body of the pot. =3D20

Also important will be the amount of friction generated at the point =3D
where the tea leaves contact with the spout. You could look at dividing =
=3D
the force vector from initial flow of the tea into horizontal and =3D
vertical vectors. The larger the horizontal and the smaller the =3D
vertical the more likely the tea will be not to drip down the spout. =3D20

So basically what you want for a teapot to pour well is good velocity =3D
of the tea, low friction at the spout, and maximum horizontal component =
=3D
of the velocity.

Paul

On Mon, Nov 28, 2011 at 11:57 PM, ivor and olive lewis =3D
wrote:

My teapots must be in the prime of life . I cannot recall ever =3D
having made a teapot that suffered from this affliction.
I have See Robin Hopper, "Functional Pottery." Fig 9.'30. p 147, ed =3D
1986 Quote, "Vent hole in lid helps by creating a passage of air which =3D
pushes the liquid out.". My apology to Mel.
I'm still working on the physics of this issue.
Best regards,
Ivor
Subject: What makes some teapots dribble ?

Hello Ivor, this really gave me a chuckle: "Which leaves the =3D
question hanging. What makes some teapots dribble?" When I think of =3D
humans, which ones do the dribbling? I think it is mostly the very young =
=3D
and the very old. So these teapots must either be very young or very old =
=3D
QED!
That Xmas cake sounds delicious.

Kind regards from
Fay, and Ralph Loewenthal

### Paul Haigh on wed 30 nov 11

If you mean dribble whilst pouring- I find that having a spout that continu=
ously narrows keeps the water pouring well. This acts to "focus" the water =
stream and keep it shooting out by simple Bernouli principle. I look at som=
e spouts and instinctively know that the water will get splashy near the op=
ening as they widen.

I make a continuously narrowing spout. If you round the clay at the tip, th=
en it will create a disturbance in the force... err flow... so use a wooden=
tool to make sure there's a continuous wall right to the edge. Then you ca=
n even pull a slight spout as you would for a pitcher, which reduces dribbl=
e when you stop pouring as well. The spout twists in the direction it was t=
hrown, so if you do make a pulled or shaped end you can account for this so=
that it twists into place when fired.

This takes a little experimenting- good luck!

Paul Haigh
Wiley Hill Mudworks
Web: http://wileyhill.com
etsy: http://www.etsy.com/shop/WileyHillMudworks

### ivor and olive lewis on thu 1 dec 11

Dear John McClure

Thank you for contributing to this thread.

I have solved this problem to my own satisfaction based on my own
observations.

Regards,

Ivor

### Eva Gallagher on fri 30 mar 12

I have to agree - we did a teapot critique at our guild with everyone
bringing in all sorts of teapots - handmade as well as commercial. The ones
that flared at the end all gurgled when they poured. Before this demo I
thought what is the big deal about a teapot gurgling when pouring - but whe=
n
you saw a teapot that poured silently next to it - it was beautiful and
elegant compared to clunky and a rather inept pour.
Eva Gallagher
Deep River, Ontario
http://newfoundoutpotter.blogspot.com/
http://www.valleyartisans.com/gallagher/Gallagher.htm
----- Original Message -----
From: "Paul Haigh"
To:
Sent: Wednesday, November 30, 2011 9:36 AM
Subject: Re: What makes some teapots dribble ?

> If you mean dribble whilst pouring- I find that having a spout that
> continuously narrows keeps the water pouring well. This acts to "focus"
> the water stream and keep it shooting out by simple Bernouli principle. I
> look at some spouts and instinctively know that the water will get splash=
y
> near the opening as they widen.
>
> I make a continuously narrowing spout. If you round the clay at the tip,
> then it will create a disturbance in the force... err flow... so use a
> wooden tool to make sure there's a continuous wall right to the edge. The=
n
> you can even pull a slight spout as you would for a pitcher, which reduce=
s
> dribble when you stop pouring as well. The spout twists in the direction
> it was thrown, so if you do make a pulled or shaped end you can account
> for this so that it twists into place when fired.
>
> This takes a little experimenting- good luck!
>
>
> Paul Haigh
> Wiley Hill Mudworks
> Web: http://wileyhill.com