George Chechopoulos on wed 4 may 11
To all you Physics & Chemistry minded Potters out there:
I'm getting ready to run another Thermal Shock Test on my Flameware bowl
that was suggested to me by Ivor Lewis. Even though the thermal shock
testing that I show in my latest video shows that my clay body and glaze ca=
n
withstand punishment far in excess of normal stove top and oven use, Ivor
didn't think that it showed the greatest thermal gradient across the clay
body thickness that could be achieved. So, his suggestion is to freeze
water in the bowl and then put it on the burner on high heat and see what
happens. Personally, I would never guarantee a Flameware pot or any other
pot for that matter that a customer of mine put into the freezer with food
in it due to the unique characteristic of water to expand at the freezing
point. Water expands about 6% at freezing. However, I did agree to run th=
e
experiment and see what happens.
Now for the question: I have searched the internet for hours over the last
couple of days and can't find an answer to this question. When water is
placed in a rigid open cylindrical container and then placed in the freezer
does the force of the expanding ice simply take the path of least resistanc=
e
(in this case upward) or is there some amount of force exerted in all
directions? When water freezes it freezes from the top down or in this
case, from the outside surfaces inward since it is contained in a bowl.
This would suggest to me that there has to be some expansion force being
exerted in all directions upon freezing.
So this is what I have found through another simple experiment: I took a
flexible plastic cottage cheese container and filled it with water and put
it in the freezer. When it froze I examined the container and saw that
there was no deformation of the container on the vertical cylindrical
exterior surface but the freezing water did exert a force on the bottom of
the container, enough to split the plastic open in a cross pattern on the
bottom. There was also an expansion of the ice on the top of the container
which was expected. So it appears that all of the expansion force occurred
along the vertical axis in this case and none horizontally. But I don't
think that was actually the case since the cylindrical plastic shape of the
vertical surface is stronger than that of the flat plastic bottom shape. S=
o
my assumed conclusion from this experiment is that some force is being
exerted in all directions with the greatest force being exerted in the
upward direction if the container is an open rigid container like a clay
pot. Fractures in the ice surface at the top of the container can be seen
where the force of the freezing water below pushed up the already frozen to=
p
surface.
Anyone else have more information on the direction of expansion forces of
ice in an open container?
George J. Chechopoulos
Marrowstone Pottery
292 Merry Road, Box 193
Nordland, WA 98358
Website: www.marrowstonepottery.com
Youtube: www.youtube.com/marrowstonepots
Email: marrowstonepots@waypoint.com
Edouard Bastarache on wed 4 may 11
"When water isplaced in a rigid open cylindrical container and then placed
in the freezerdoes the force of the expanding ice simply take the path of
least resistance(in this case upward) or is there some amount of force
exerted in all
directions?" (George Chechopoulos)
Yes,
if you remember the bottles of milk that froze in winter on the porch.
Gis,
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://www.flickr.com/photos/30058682@N00/
http://edouardbastarache.blogspot.com/
http://www.facebook.com/edouard.bastarache
http://blogsalbertbastarache.blogspot.com/
David Finkelnburg on thu 5 may 11
George,
As you have obviously worked out from your test, the ice attempts to
expand equally in all directions, but actually applies pressure where it is
constrained. Your container is stronger on the sides than the bottom, and
not at all at the top, so the ice moves out the bottom and heaves up at the
top and the sides appear unchanged. You may find the sides have stretched
at least a little.
The ASTM thermal shock test should be sufficient, btw. Your bowl will
have to have a special shape to freeze ice in it without cracking. Otherwis=
e
you may get a failure on the stove that is really due to expansion of ice.
Best,
Dave Finkelnburg
http://www.mattanddavesclays.com
-----------------------------
On Wed, 4 May 2011 11:28:02 -0700, George Chechopoulos <
marrowstonepots@WAYPOINT.COM> wrote, in part:
....When water is
placed in a rigid open cylindrical container and then placed in the freezer
does the force of the expanding ice simply take the path of least resistanc=
e
(in this case upward) or is there some amount of force exerted in all
directions?
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