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## calulating the amount of clay in a slip

### John Rodgers on fri 10 aug 07

Miles,

I do this. Works every time.

Weigh equal volumes of water and slip. Say, one pint of water and one
pint of slip. Subtract the weight of the water from the weight of the
slip. What is left is the weight of the solids in the slip. Easy.

To get the specific gravity of density, simply divide the weight of the
slip by the weight of the water. Easy.

If you have a known volume of slip - like say 4 gallons in a five gallon
bucket - and say it is made up of reclaimed clay - trimmings, etc, -
knowing how to arrive at the density of the slip allows one to be able
to calculate how much water to add to the bucket to reduce the density
to a particular lower number or density, or you can calculate how much
clay to add to the slip to increase the density. Math is a wonderful thing.

John Rodgers
Chelsea, AL

Miles Smith wrote:
> Miles Smith Pottery on Aug.10 2007
>
> I stirred the pot trimmings with the throwing water and go a soft mash potato like slip I sieved out the chucks and weighed 100cc of the slip. It was 158g. I have a Hydrometer and it stood up in the thickness only in as far as covering the bulb. I calculated the specific Gravity by extending the graduate lines down toward the bulb and noted that the SG should be around 2.780.
> I went to Google and asked , "What is the weight of water?"
> www.onlineconversion.com/waterweight.htm told me 100cc = 100g.
>
> MY QUESTION; Do I have 58g of dry ingredients in the 100cc graduate? If yes can you explain why my Hydrometer didn't sink to the 1.58 Specific Gravity line?
>
> If the Hydrometer is right and I have 278g of dry clay in the graduate, how do I calculate how much of the 158g sample weight in the 100cc graduate is water? (I know I don't have 100cc of water in the graduate.)
>
> Ps; I need to know the dry weights of material in my slips so I can make repetitive colorant additions.
>
> Thanks, Miles
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
>
>
>

### Miles Smith on fri 10 aug 07

Miles Smith Pottery on Aug.10 2007

I stirred the pot trimmings with the throwing water and go a soft mash =
potato like slip I sieved out the chucks and weighed 100cc of the slip. =
It was 158g. I have a Hydrometer and it stood up in the thickness only =
in as far as covering the bulb. I calculated the specific Gravity by =
extending the graduate lines down toward the bulb and noted that the SG =
should be around 2.780.
I went to Google and asked , "What is the weight of water?"
www.onlineconversion.com/waterweight.htm told me 100cc =3D 100g.

MY QUESTION; Do I have 58g of dry ingredients in the 100cc graduate? If =
yes can you explain why my Hydrometer didn't sink to the 1.58 Specific =
Gravity line?

If the Hydrometer is right and I have 278g of dry clay in the graduate, =
how do I calculate how much of the 158g sample weight in the 100cc =
graduate is water? (I know I don't have 100cc of water in the graduate.)

Ps; I need to know the dry weights of material in my slips so I can make =

Thanks, Miles

### Lee Love on fri 10 aug 07

On 8/10/07, Miles Smith wrote:
>
> ple weight in the 100cc graduate is water? (I know I don't have 100cc of
>
> Ps; I need to know the dry weights of material in my slips so I can make
>
> Thanks, Miles

Dry the slip, then weigh it.

--
Lee in Minneapolis, Minnesota USA
discussion on Beauty:

http://journals.fotki.com/togeika/beauty/

http://mashikopots.blogspot.com/

"Let the beauty we love be what we do." - Rumi

### John Rodgers on sat 11 aug 07

John,

I would only add a comment to your presentation here: It behooves anyone
who really wants control over their processes to fully understand the
principles and the math you have presented here. It allows one to be
able to fully manipulate ones materials and get the absolute best use of
them, as well as increase ones efficiency in working with them. Taking
out the guesswork and having control over ones work is what it is all
about. Do this, and one can truly and justifiably be called "Master".

Regards,

John Rodgers
Chelsea, AL

John Hesselberth wrote:
> On Aug 11, 2007, at 12:46 AM, John Rodgers wrote:
>
>> Weigh equal volumes of water and slip. Say, one pint of water and one
>> pint of slip. Subtract the weight of the water from the weight of the
>> slip. What is left is the weight of the solids in the slip. Easy.
>
> John, this gives what Hamer and Hamer call the "apparent dry weight"
> of the slip. What is needed here is Brongniart's Formula. Hamer and
> Hamer describe it under "Formula" in their book, but I have copied
> below a (to me) simpler description originally posted to Clayart by
> Stuart Altmann back in 1998.
>
> Miles, the reason your hydrometer didn't sink to 1.58 may be that
> hydrometers become inaccurate in thick viscous slips. They work well
> for thin slips like terra sig, but weighing 100 ml like you did is
> more accurate for thick slips.
>
> Regards,
>
> John
>
> --------
>
>> Brongniart's formula enables one to estimate the amount of dry
>> material in a
>> given volume of "slop," that is, of a glaze or slip already mixed with
>> water. This formula has a number of uses, as will be described
>> below. But
>> first, let me present the formula, here expressed in convenient metric
>> units. The only measurement that you need to make is to determine the
>> density of your slop, by weighing one liter of it, in grams. Then
>> plug that
>> density value into Brongniart's formula:
>>
>>
>>
>> grams of dry matter per liter of slop
>>
>>
>> (density of slop - density of water) (density of dry matter)
>> = ____________________________________________________________
>> (density of dry matter - density of water)
>>
>>
>> Because the density of dry matter in most non-lead glazes is about
>> 2500 g/l
>> and the density of water is about 1000 g/l, the formula simplifies to:
>>
>> g dry matter per liter of slop = (density of slop - 1000) 5/3
>>
>>
>> So, for example, suppose that a liter of your glaze slop weighs
>> 1500 g.
>> Then the amount of dry material in it is (1500-1000)5/3 = 833.3 g
>> dry matter
>> per liter. And since the total slop mass is 1500 g, we also know
>> that the
>> glaze slop contains 1500-833.3 = 666.7 g water per liter of slop.
>>
>> For most purposes, this formula is accurate enough. For greater
>> accuracy,
>> you (or your glaze program) can calculate the actual density of
>> glaze and you can determine the actual density of your local water
>> at your
>> room temperature.
>>
>> (In various common references, including the standard dictionaries and
>> encyclopedias of ceramics, you will find more obscure versions of
>> Brongniart's formula, with terms like "apparent dry weight" that
>> need to be
>> explained. By sticking with standard metric measures, one obtains
>> the above
>> simple version.)
>>
>> Here are three uses I have found for Brongniart's formula. I would be
>> interested to hear of others.
>>
>> 1. Suppose you have a bucket of glaze slop--maybe not even a full
>> recipe's
>> worth and perhaps a bit thicker now as a result of evaporation. You
>> would
>> like to try adding, say, 1% cobalt carbonate to a sample of it, to
>> tint the
>> glaze blue. But that's 1% of the dry glaze, and you don't know how
>> much dry
>> matter there is in a given volume of slop. Mix your glaze very well,
>> including scrapings from the sides of the bucket, weigh a liter of
>> it, apply
>> Brongniart's formula, then add cobalt carb at 1% of the dry matter.
>> Simple.
>>
>> 2. Most stoneware glazes that are applied by dipping work best at a
>> density
>> of about 1500 g/l (i.e. a specific gravity of 1.5) Suppose you are
>> making
>> up 14 kg of a glaze and want to know how much water would bring the
>> slop to
>> that density. The amount of water that would make a liter of slop
>> with a
>> density of 1500 g/l can be found by using Brongniart's formula, and
>> in fact
>> we have also done so, in the illustration above, because we assumed
>> for
>> purposes of illustration that slop density was 1500. The result was a
>> mixture that for every 833.3 g dry matter contains 666.7 g (666.7
>> ml) water.
>> That is, the water added per 833.3 g dry glaze material is
>> 666.7/833.3 =
>> 80%. So, our hypothetical batch of 14 kg dry matter would require an
>> addition of 80% of 14 kg water, i.e. 11.2 kg ( 11.2 liters) of water.
>>
>> 3. I recently made up a new glaze with the amount of water
>> calculated to
>> bring the density to 1500 g/l, but what I got was something too
>> thick to be
>> a normal glaze, and sure enough its density was too high, well
>> above 1500.
>> Assuming that I had weighed out one ingredient twice (the
>> ingredients were
>> weighed out over a two-day period), I calculated the total amount
>> of dry
>> material in my bucket. It was very close to 600 g above what it
>> should have
>> been; only one of the ingredients in my glaze was called for in that
>> amount.
>>
>> Stuart Altmann
>
> ______________________________________________________________________________
>
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
>
>

### Lynne and Bruce Girrell on sat 11 aug 07

Miles Smith wrote:
>how do I calculate how much of the 158g sample weight in the 100cc graduate
>is water?

You need Brongniart's formula

http://www.potters.org/subject11877.htm

Bruce Girrell

_________________________________________________________________
Learn.Laugh.Share. Reallivemoms is right place!
http://www.reallivemoms.com?ocid=TXT_TAGHM&loc=us

### John Sankey on sat 11 aug 07

Miles Smith Pottery on Aug.10 2007:
"I stirred the pot trimmings with the throwing water and got a
soft mash potato like slip I sieved out the chucks and weighed
100cc of the slip. It was 158g. I have a Hydrometer and it stood
up in the thickness only in as far as covering the bulb. I
calculated the specific Gravity by extending the graduate lines
down toward the bulb and noted that the SG should be around 2.780
... MY QUESTION; Do I have 58g of dry ingredients in the 100cc

No, you have more. The dry ingredients are occupying part of the
volume so there is less than 100 cc of water in your 100 cc of
slip. Put your 100 cc of slip into a dish and let it dry in a
warm oven to get the dry weight.

"can you explain why my Hydrometer didn't sink to the 1.58
Specific Gravity line?"

Hydrometers are accurate only for liquids. Glazes often aren't,
and slips definitely aren't. Your SG is 1.58

For repetitive colour additions you want a measurement you can
do non-destructively. As long as you stick to the same clay, the
weight of 100 cc of slip will be a stable measure.

--

### John Hesselberth on sat 11 aug 07

On Aug 11, 2007, at 12:46 AM, John Rodgers wrote:

> Weigh equal volumes of water and slip. Say, one pint of water and one
> pint of slip. Subtract the weight of the water from the weight of the
> slip. What is left is the weight of the solids in the slip. Easy.

John, this gives what Hamer and Hamer call the "apparent dry weight"
of the slip. What is needed here is Brongniart's Formula. Hamer and
Hamer describe it under "Formula" in their book, but I have copied
below a (to me) simpler description originally posted to Clayart by
Stuart Altmann back in 1998.

Miles, the reason your hydrometer didn't sink to 1.58 may be that
hydrometers become inaccurate in thick viscous slips. They work well
for thin slips like terra sig, but weighing 100 ml like you did is
more accurate for thick slips.

Regards,

John

--------

> Brongniart's formula enables one to estimate the amount of dry
> material in a
> given volume of "slop," that is, of a glaze or slip already mixed with
> water. This formula has a number of uses, as will be described
> below. But
> first, let me present the formula, here expressed in convenient metric
> units. The only measurement that you need to make is to determine the
> density of your slop, by weighing one liter of it, in grams. Then
> plug that
> density value into Brongniart's formula:
>
>
>
> grams of dry matter per liter of slop
>
>
> (density of slop - density of water) (density of dry matter)
> = ____________________________________________________________
> (density of dry matter - density of water)
>
>
> Because the density of dry matter in most non-lead glazes is about
> 2500 g/l
> and the density of water is about 1000 g/l, the formula simplifies to:
>
> g dry matter per liter of slop = (density of slop - 1000) 5/3
>
>
> So, for example, suppose that a liter of your glaze slop weighs
> 1500 g.
> Then the amount of dry material in it is (1500-1000)5/3 = 833.3 g
> dry matter
> per liter. And since the total slop mass is 1500 g, we also know
> that the
> glaze slop contains 1500-833.3 = 666.7 g water per liter of slop.
>
> For most purposes, this formula is accurate enough. For greater
> accuracy,
> you (or your glaze program) can calculate the actual density of
> glaze and you can determine the actual density of your local water
> at your
> room temperature.
>
> (In various common references, including the standard dictionaries and
> encyclopedias of ceramics, you will find more obscure versions of
> Brongniart's formula, with terms like "apparent dry weight" that
> need to be
> explained. By sticking with standard metric measures, one obtains
> the above
> simple version.)
>
> Here are three uses I have found for Brongniart's formula. I would be
> interested to hear of others.
>
> 1. Suppose you have a bucket of glaze slop--maybe not even a full
> recipe's
> worth and perhaps a bit thicker now as a result of evaporation. You
> would
> like to try adding, say, 1% cobalt carbonate to a sample of it, to
> tint the
> glaze blue. But that's 1% of the dry glaze, and you don't know how
> much dry
> matter there is in a given volume of slop. Mix your glaze very well,
> including scrapings from the sides of the bucket, weigh a liter of
> it, apply
> Brongniart's formula, then add cobalt carb at 1% of the dry matter.
> Simple.
>
> 2. Most stoneware glazes that are applied by dipping work best at a
> density
> of about 1500 g/l (i.e. a specific gravity of 1.5) Suppose you are
> making
> up 14 kg of a glaze and want to know how much water would bring the
> slop to
> that density. The amount of water that would make a liter of slop
> with a
> density of 1500 g/l can be found by using Brongniart's formula, and
> in fact
> we have also done so, in the illustration above, because we assumed
> for
> purposes of illustration that slop density was 1500. The result was a
> mixture that for every 833.3 g dry matter contains 666.7 g (666.7
> ml) water.
> That is, the water added per 833.3 g dry glaze material is
> 666.7/833.3 =
> 80%. So, our hypothetical batch of 14 kg dry matter would require an
> addition of 80% of 14 kg water, i.e. 11.2 kg ( 11.2 liters) of water.
>
> 3. I recently made up a new glaze with the amount of water
> calculated to
> bring the density to 1500 g/l, but what I got was something too
> thick to be
> a normal glaze, and sure enough its density was too high, well
> above 1500.
> Assuming that I had weighed out one ingredient twice (the
> ingredients were
> weighed out over a two-day period), I calculated the total amount
> of dry
> material in my bucket. It was very close to 600 g above what it
> should have
> been; only one of the ingredients in my glaze was called for in that
> amount.
>
> Stuart Altmann

### Sylvia Holmes on sat 11 aug 07

Hello Miles
Though far from an expert, I'll add my voice and agree
Brongniart's formula is the way to get predictable and
repeatable results with coloured slips. I've tried all
the other ways and this is the dependable one. It
demands a bit of method, but it's worth it. As an ex
painter (to whom colour control is crucial) I have
found the best way to go is to make strong coloured
slips using the formula and following the
manufacturers recommendations as regards maximum
proportion of stains/oxides to add. You can then
dilute the strong (crude!) colours by volume with
plain slurry or with white slip, or mix two or several
slips together by volume to make other colours/shades
(testing all the time and keeping records of course).
You always have the base line of your strong basic
can repeat combinations you like as required, as long
as you keep those records.

I'd like to add a query of my own - I am struggling to
find a good high temperature green stain here in the
uk for stoneware slips, which doesn't go black or
bleed all over the place. Does anyone have any
suggestions/explanations?

Thanks
Sylvia, here in the UK where summer's finally arrived:
late, but better than never.

--- John Hesselberth wrote:

> On Aug 11, 2007, at 12:46 AM, John Rodgers wrote:
>
> > Weigh equal volumes of water and slip. Say, one
> pint of water and one
> > pint of slip. Subtract the weight of the water
> from the weight of the
> > slip. What is left is the weight of the solids in
> the slip. Easy.
>
> John, this gives what Hamer and Hamer call the
> "apparent dry weight"
> of the slip. What is needed here is Brongniart's
> Formula. Hamer and
> Hamer describe it under "Formula" in their book, but
> I have copied
> below a (to me) simpler description originally
> posted to Clayart by
> Stuart Altmann back in 1998.
>
> Miles, the reason your hydrometer didn't sink to
> 1.58 may be that
> hydrometers become inaccurate in thick viscous
> slips. They work well
> for thin slips like terra sig, but weighing 100 ml
> like you did is
> more accurate for thick slips.
>
> Regards,
>
> John
>
> --------
>
> > Brongniart's formula enables one to estimate the
> amount of dry
> > material in a
> > given volume of "slop," that is, of a glaze or
> > water. This formula has a number of uses, as will
> be described
> > below. But
> > first, let me present the formula, here expressed
> in convenient metric
> > units. The only measurement that you need to make
> is to determine the
> > density of your slop, by weighing one liter of it,
> in grams. Then
> > plug that
> > density value into Brongniart's formula:
> >
> >
> >
> > grams of dry matter per liter of slop
> >
> >
> > (density of slop - density of water) (density of
> dry matter)
> > =
>
____________________________________________________________
> > (density of dry matter - density of water)
> >
> >
> > Because the density of dry matter in most non-lead
> > 2500 g/l
> > and the density of water is about 1000 g/l, the
> formula simplifies to:
> >
> > g dry matter per liter of slop = (density of slop
> - 1000) 5/3
> >
> >
> > So, for example, suppose that a liter of your
> glaze slop weighs
> > 1500 g.
> > Then the amount of dry material in it is
> (1500-1000)5/3 = 833.3 g
> > dry matter
> > per liter. And since the total slop mass is 1500
> g, we also know
> > that the
> > glaze slop contains 1500-833.3 = 666.7 g water per
> liter of slop.
> >
> > For most purposes, this formula is accurate
> enough. For greater
> > accuracy,
> > you (or your glaze program) can calculate the
> actual density of
> > glaze and you can determine the actual density of
> > at your
> > room temperature.
> >
> > (In various common references, including the
> standard dictionaries and
> > encyclopedias of ceramics, you will find more
> obscure versions of
> > Brongniart's formula, with terms like "apparent
> dry weight" that
> > need to be
> > explained. By sticking with standard metric
> measures, one obtains
> > the above
> > simple version.)
> >
> > Here are three uses I have found for Brongniart's
> formula. I would be
> > interested to hear of others.
> >
> > 1. Suppose you have a bucket of glaze slop--maybe
> not even a full
> > recipe's
> > worth and perhaps a bit thicker now as a result of
> evaporation. You
> > would
> > like to try adding, say, 1% cobalt carbonate to a
> sample of it, to
> > tint the
> > glaze blue. But that's 1% of the dry glaze, and
> you don't know how
> > much dry
> > matter there is in a given volume of slop. Mix
> > including scrapings from the sides of the bucket,
> weigh a liter of
> > it, apply
> > Brongniart's formula, then add cobalt carb at 1%
> of the dry matter.
> > Simple.
> >
> > 2. Most stoneware glazes that are applied by
> dipping work best at a
> > density
> > of about 1500 g/l (i.e. a specific gravity of 1.5)
> Suppose you are
> > making
> > up 14 kg of a glaze and want to know how much
> water would bring the
> > slop to
> > that density. The amount of water that would make
> a liter of slop
> > with a
> > density of 1500 g/l can be found by using
> Brongniart's formula, and
> > in fact
> > we have also done so, in the illustration above,
> because we assumed
> > for
> > purposes of illustration that slop density was
> 1500. The result was a
> > mixture that for every 833.3 g dry matter contains
> 666.7 g (666.7
> > ml) water.
> > That is, the water added per 833.3 g dry glaze
> material is
> > 666.7/833.3 =
> > 80%. So, our hypothetical batch of 14 kg dry
> matter would require an
> > addition of 80% of 14 kg water, i.e. 11.2 kg (
> 11.2 liters) of water.
> >
> > 3. I recently made up a new glaze with the amount
> of water
> > calculated to
> > bring the density to 1500 g/l, but what I got was
> something too
> > thick to be
> > a normal glaze, and sure enough its density was
> too high, well
> > above 1500.
> > Assuming that I had weighed out one ingredient
> twice (the
> > ingredients were
> > weighed out over a two-day period), I calculated
> the total amount
> > of dry
> > material in my bucket. It was very close to 600 g
> above what it
> > should have
> > been; only one of the ingredients in my glaze was
> called for in that
> > amount.
> >
> > Stuart Altmann
>
>
______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be
>

___________________________________________________________
Yahoo! Answers - Got a question? Someone out there knows the answer. Try it
now.

### Lee Love on sat 11 aug 07

Another way is to do a lineblend of colorant in a set mixture of slip.

--
Lee in Minneapolis, Minnesota USA
discussion on Beauty:

http://journals.fotki.com/togeika/beauty/

http://mashikopots.blogspot.com/

"Let the beauty we love be what we do." - Rumi

### Ivor and Olive Lewis on sun 12 aug 07

<pint of slip. Subtract the weight of the water from the weight of the =
slip. What is left is the weight of the solids in the slip. Easy.>>
Dear John Rodgers,

Correct me if I an wrong, but this seems to say that the mineral content =
of the Slip has Mass but no volume.

Brongniart's Formula can be used for the calculation of the dry weight =
of solids suspended in a slip. This is given as Appendix 4, page 269 in =
M. Cardew, "Pioneer Pottery.".=20

The example is given in Imperial Measure but it should not be hard to =
convert to metric units.

Best regards,

Ivor Lewis.
Redhill,
South Australia.

### John Rodgers on sun 12 aug 07

With encouragement - and gentle prodding I might add - of John Sankey
and Ivor Lewis, I went back and took another look at my method of slip
calculation. I was wrong! Imagine that! First time ever in my whole
life! Imagine my shock. LOL!

John and Ivor are correct. There is less water in the pint of slip that
was discussed, because the clay occupies some of the space or volume in
the pint, thereby displacing some of the water that I said was there. I
stand corrected. With the pint as the unit of measure, the amount of
water contained therein is greater than the amount of water in a pint of
slip.

Brongniart's had it right, and Brongniart's Formula is the way to go to
calculate that amount of clay in the slip.

Sheesh! It's to early in the morning to have to deal with this stuff,
but right is right.

Regards,

John Rodgers
Chelsea, AK

John Rodgers wrote:
> Miles,
>
> I do this. Works every time.
>
> Weigh equal volumes of water and slip. Say, one pint of water and one
> pint of slip. Subtract the weight of the water from the weight of the
> slip. What is left is the weight of the solids in the slip. Easy.
>
> To get the specific gravity of density, simply divide the weight of the
> slip by the weight of the water. Easy.
>
> If you have a known volume of slip - like say 4 gallons in a five gallon
> bucket - and say it is made up of reclaimed clay - trimmings, etc, -
> knowing how to arrive at the density of the slip allows one to be able
> to calculate how much water to add to the bucket to reduce the density
> to a particular lower number or density, or you can calculate how much
> clay to add to the slip to increase the density. Math is a wonderful
> thing.
>
> John Rodgers
> Chelsea, AL
>
>
> Miles Smith wrote:
>> Miles Smith Pottery on Aug.10 2007
>>
>> I stirred the pot trimmings with the throwing water and go a soft
>> mash potato like slip I sieved out the chucks and weighed 100cc of
>> the slip. It was 158g. I have a Hydrometer and it stood up in the
>> thickness only in as far as covering the bulb. I calculated the
>> specific Gravity by extending the graduate lines down toward the bulb
>> and noted that the SG should be around 2.780.
>> I went to Google and asked , "What is the weight of water?"
>> www.onlineconversion.com/waterweight.htm told me 100cc = 100g.
>>
>> MY QUESTION; Do I have 58g of dry ingredients in the 100cc graduate?
>> If yes can you explain why my Hydrometer didn't sink to the 1.58
>> Specific Gravity line?
>>
>> If the Hydrometer is right and I have 278g of dry clay in the
>> graduate, how do I calculate how much of the 158g sample weight in
>> the 100cc graduate is water? (I know I don't have 100cc of water in
>>
>> Ps; I need to know the dry weights of material in my slips so I can
>>
>> Thanks, Miles
>>
>> ______________________________________________________________________________
>>
>> Send postings to clayart@lsv.ceramics.org
>>
>> You may look at the archives for the list or change your subscription
>> settings from http://www.ceramics.org/clayart/
>>
>> Moderator of the list is Mel Jacobson who may be reached at
>>
>>
>>
>
> ______________________________________________________________________________
>
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### John Rodgers on sun 12 aug 07

Ivor,

Thanks for the review. I have publicly corrected myself. Hopefully those
who read my mis-information will see the correction and make the same.

Regards,

John

Ivor and Olive Lewis wrote:
> <>
> Dear John Rodgers,
>
> Correct me if I an wrong, but this seems to say that the mineral content of the Slip has Mass but no volume.
>
> Brongniart's Formula can be used for the calculation of the dry weight of solids suspended in a slip. This is given as Appendix 4, page 269 in M. Cardew, "Pioneer Pottery.".
>
> The example is given in Imperial Measure but it should not be hard to convert to metric units.
>
> Best regards,
>
> Ivor Lewis.
> Redhill,
> South Australia.
>
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### Ivor and Olive Lewis on mon 13 aug 07

Dear John Rodgers=20

Your candour is appreciated. Some ideas are complex and it takes time =
for the fundamental principle to emerge as part of our understanding of =