Anne K. Wellings on sat 5 jan 02
When weighing out bagged clay for throwing, I divide the standard
25-pound pug into a standard number of portions depending on the item and
then weigh the portions to get them even. So, for example, what I call a
3-pound bowl is made from one-eighth of a pug, which is really a bit more
than 3 pounds. My theory has been that all pugs should be the same amount
of clay since they should all be mixed at about the same consistency, but
that later loss of moisture could affect the weight, so the weight could
be different according to how hard or soft the clay is. So I do it this
way instead of weighing the pieces according to an exact weight. Also, it
just seems more efficient to divide a whole pug than to have bits left
over.
The weird thing is, I have noticed that often a softer pug of clay will
appear to weigh less than a harder one.
I would expect to opposite to be true, because of the water content of
the softer clay. This suggests to me that either the clay is not always
mixed and bagged at the same consistency, or that the pugs are not all
the same size. Logically, a harder, heavier bag of clay has more clay in
it and, if divided into equal portions, will result in bigger pots than a
softer but lighter one of the same size. But if I go the other route and
divide the clay strictly by weight, I will still be dealing with
different amounts of clay if the softness varies. As an added annoyance,
some parts of the pug are often softer than others depending on which
side was on the edge of the box and how long it sat around.
How does anyone else deal with this, or do you just ignore it? I suppose
I could have clay specially mixed to my specifications of hardness and
always use it as fresh as possible. But I would have to change clays, as
the one I prefer to use is shipped to my local supplier from another
state. My supplier makes great clays, but not of the color that has been
working for my product line.
Anne
Mike Gordon on sun 6 jan 02
Anne,
If you use commercially mixed clay these are the problems you will
encounter. I don't know what clay you use or which state you live in,
but I am guessing it is an industry wide problem.As you have read on
this list most potters that rely on their production line for their sole
income in most cases either make their own clay or have their personal
preference made for them and in ton quantities. As for the clay being
dryer on the outside than the inside try banging the whole 25lb. bag in
it's plastic bag on the ground several times on each side. This will
help, it's like trowling cement, it brings the moisture to the surface.
Mike Gordon, Walnut Creek, Ca.
Snail Scott on sun 6 jan 02
At 07:22 PM 1/5/02 -0800, you wrote:
>The weird thing is, I have noticed that often a softer pug of clay will
>appear to weigh less than a harder one.
>I would expect to opposite to be true, because of the water content of
>the softer clay.
Yeah, but clay (tiny little rocks) weighs more than water. -Snail
David Hendley on sun 6 jan 02
Anne, I can't help but think that you are thinking too much.
Don't get me wrong, thinking is a good thing, and I enjoyed
reading your thought processes about the weight of clay.
In my experience, pugs of clay vary significantly, plus or
minus, from 25 pounds each.
At the manufacturer's pugmill, if the cut-off wire misses the
mark by just 1/8th of an inch, on an 8-inch-square extrusion,
that is a significant weight difference.
I also don't see how you could possibly divide a piece of
clay into 8 equal pieces anywhere close to accurately.
I sure couldn't. Even if I measured before cutting, I couldn't keep
the wire going perfectly straight and would end up with
a lot of variation.
In my mind, you want clay of equal consistency if you are
making, for example, eight 3-pound pots. So, I would
wedge or kneed the clay BEFORE cutting it into 3 pound
balls. It's also faster and easier, for me anyway, to knead
larger amounts of clay. I would divide the block into
convenient amounts (9 pounds), knead, and then divide
into 3 pound balls.
Your worry that if you 'divide the clay strictly by weight, you
will be dealing with different amounts of clay if the softness varies',
is unfounded. We're talking about handmade pottery here.
Even if there is a variance in the weight-to-volume ratio,
there will be variations in wall thickness, bottom thickness,
diameter, and height that are more infinitely significant that
starting with 10 grams less clay than usual.
You say
>I could have clay specially mixed to my specifications of hardness
Maybe in your dreams or in a perfect world.
Clay is always going to vary, in spite of the clay company's best
efforts to please you.
David Hendley
Maydelle, Texas
hendley@tyler.net
http://www.farmpots.com
----- Original Message -----
From: "Anne K. Wellings"
To:
Sent: Saturday, January 05, 2002 7:22 PM
Subject: weight of a pug of clay
> When weighing out bagged clay for throwing, I divide the standard
> 25-pound pug into a standard number of portions depending on the item and
> then weigh the portions to get them even. So, for example, what I call a
> 3-pound bowl is made from one-eighth of a pug, which is really a bit more
> than 3 pounds. My theory has been that all pugs should be the same amount
> of clay since they should all be mixed at about the same consistency, but
> that later loss of moisture could affect the weight, so the weight could
> be different according to how hard or soft the clay is. So I do it this
> way instead of weighing the pieces according to an exact weight. Also, it
> just seems more efficient to divide a whole pug than to have bits left
> over.
>
> The weird thing is, I have noticed that often a softer pug of clay will
> appear to weigh less than a harder one.
> I would expect to opposite to be true, because of the water content of
> the softer clay. This suggests to me that either the clay is not always
> mixed and bagged at the same consistency, or that the pugs are not all
> the same size. Logically, a harder, heavier bag of clay has more clay in
> it and, if divided into equal portions, will result in bigger pots than a
> softer but lighter one of the same size. But if I go the other route and
> divide the clay strictly by weight, I will still be dealing with
> different amounts of clay if the softness varies. As an added annoyance,
> some parts of the pug are often softer than others depending on which
> side was on the edge of the box and how long it sat around.
>
> How does anyone else deal with this, or do you just ignore it? I suppose
> I could have clay specially mixed to my specifications of hardness and
> always use it as fresh as possible. But I would have to change clays, as
> the one I prefer to use is shipped to my local supplier from another
> state. My supplier makes great clays, but not of the color that has been
> working for my product line.
>
> Anne
>
Anne Wellings on mon 7 jan 02
On Sun, 6 Jan 2002 20:47:56 -0800, David Hendley wrote:
>Anne, I can't help but think that you are thinking too much.
(clip)
>I also don't see how you could possibly divide a piece of
>clay into 8 equal pieces anywhere close to accurately.
>I sure couldn't. Even if I measured before cutting, I couldn't keep
>the wire going perfectly straight and would end up with
>a lot of variation.
>
>In my mind, you want clay of equal consistency if you are
>making, for example, eight 3-pound pots. So, I would
>wedge or kneed the clay BEFORE cutting it into 3 pound
>balls. It's also faster and easier, for me anyway, to knead
>larger amounts of clay. I would divide the block into
>convenient amounts (9 pounds), knead, and then divide
>into 3 pound balls.
Thanks, David, and you're probably right about me thinking too much.
I do want to clarify that I do indeed weigh the clay pieces with a scale
after cutting the pug into 8 pieces and then add or subtract to make them
even. It's just that I divide the whole pug that way rather than weighing
out 3-pound pieces and then having some left over. So the pieces end up
being slightly more than 3 pounds depending on the weight of the pug.
I may try your method of wedging bigger pieces and dividing them. But to me
it seems easier to divide the pug into the right number of pieces first and
then adjust their weight. Plus, I like to knead each piece individually
into a cone before throwing it. I have read reasons on Clayart why this
isn't good, but I have to say it works for me. No s-cracks and such. I
thoroughly pat and smooth the bottoms of the cones to get rid of any seams
or folds.
Anne
Anne Wellings on mon 7 jan 02
On Sun, 6 Jan 2002 10:52:41 -0800, Snail Scott wrote:
>At 07:22 PM 1/5/02 -0800, you wrote:
>>The weird thing is, I have noticed that often a softer pug of clay will
>>appear to weigh less than a harder one.
>>I would expect to opposite to be true, because of the water content of
>>the softer clay.
>
>
>Yeah, but clay (tiny little rocks) weighs more than water. -Snail
Snail, this thought has occurred to me. But a wet pot weighs more than a
dry pot, so why wouldn't a wetter pug of clay weigh more than a drier one?
Unless we're talking about the wetter pug actually having less clay in it,
which I guess it would if it contains more water and is the same physical
size as a harder pug.
You may be absolutely right. I would love to hear some other points of
view. Does clay weigh more than water?
Anne
Snail Scott on mon 7 jan 02
At 12:55 AM 1/7/02 -0500, you wrote:
>Snail, this thought has occurred to me. But a wet pot weighs more than a
>dry pot, so why wouldn't a wetter pug of clay weigh more than a drier one?
>Unless we're talking about the wetter pug actually having less clay in it,
>which I guess it would if it contains more water and is the same physical
>size as a harder pug.
I suppose it depends on the way the pug is measured.
If it's by volume (size), a pug with more clay will
weigh more than one with more water.
If the pug is measured by weight, then a drier pug
will have more clay content than a wetter one.
To have equal volume, added water would have to
displace clay, and vice-versa, since neither is
compressible. (terms: science-type compression, not
pottery-type compression, OK?)
I don't know how many manufacturers actually weigh
their pugs; most that I know of simply extrude a
length from the pugmill to a line marked on the
table, based on previous measurements of weight for
that length, and slice it off with a fixed-position
cutter. So, effectively, clay pugs are sold by
volume, based on a presumed average weight for that
size pug. (Have you ever bought 50# boxes of clay
mail-order? UPS charges for the actual weight, which
it stamps on the box - sometimes it's 50#, sometimes
53#. (Usually a bit more than 50, which I take to be
the manufacturer erring on the side of the customer
to avoid short-weighting anyone, because of this
inherent variability in pug sizes.)
A dry pot weighs less than a wet one, true, but its
size is smaller (less volume). Density is lost too,
though, since past a certain level of dryness, the
clay is hard and won't shrink further, so any
remaining water leaves porosity behind when it
evaporates. Thus, this discussion is only relevant
to working-consistency clay.
I wonder, though, if the actual weight difference
is joined by a perceived difference. Most people
are fooled by the weight of objects when the sizes
vary widely. (Compare the apparent (perceived) weight
of a 10# bowling ball with a 10# bag of feldspar.)
Perhaps a slightly heavier (more clay/less water)
pug would feel a bit heavier still, for being smaller
in size.
-Snail
Terrance Lazaroff on mon 7 jan 02
Anne;
It is not so much weight as it is density.
Wet is heavier because it is water and dry combined.
Dry is lighter because it is absent the water.
Terry
----- Original Message -----
From: "Anne Wellings"
To:
Sent: Monday, January 07, 2002 12:55 AM
Subject: Re: weight of a pug of clay
> On Sun, 6 Jan 2002 10:52:41 -0800, Snail Scott
wrote:
>
> >At 07:22 PM 1/5/02 -0800, you wrote:
> >>The weird thing is, I have noticed that often a softer pug of clay will
> >>appear to weigh less than a harder one.
> >>I would expect to opposite to be true, because of the water content of
> >>the softer clay.
> >
> >
> >Yeah, but clay (tiny little rocks) weighs more than water. -Snail
>
> Snail, this thought has occurred to me. But a wet pot weighs more than a
> dry pot, so why wouldn't a wetter pug of clay weigh more than a drier one?
> Unless we're talking about the wetter pug actually having less clay in it,
> which I guess it would if it contains more water and is the same physical
> size as a harder pug.
>
> You may be absolutely right. I would love to hear some other points of
> view. Does clay weigh more than water?
>
> Anne
>
>
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Carl Finch on mon 7 jan 02
At 12:55 AM 1/7/02 -0500, you wrote:
> Does clay weigh more than water?
Anne, it's almost 1:00 AM--get to bed!!
When you awaken, take a ball of clay and drop it into a bucket of
water. That which weighs more will be on the bottom, and that which weighs
less, on top!
(I couldn't bring myself to send this reply to the list!!)
Best wishes,
--Carl
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