[Clayart] Lithium, Zinc and food safety at Cone 6

[The Fuzzy Chef]

All,

A lot of Cone 6 Glaze recipes contain minor amounts of Zinc Oxide and/or
Lithium Carbonate as fluxes. Both of these metals are toxic, however,
and MC6G doesn't think much of them food-safety-wise. However, I'd like
to get some additional opinions:

1) Can Cone 6 glazes which contain Lithium and/or Zinc Oxide be food safe?

2) If so, typically what % tip the balance (obviously there's other
factors here)?

3) Do you use Lithium/Zinc in your Cone 6 glazes?

--
--Josh "Fuzzy Chef" Berkus
blog: http://www.fuzzychef.org
pics: http://fuzzychef.smugmug.com
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[John Hesselberth]

Hi Josh,

We don't think much of lithium carbonate because we have seen some really strange behavior when it is used at levels above 2% -- like shivering and crazing on the same pot. Shivering is something to be avoided at all costs on functional work. We have not seen that kind of problem with lithium sourced from spodumene. If the glaze is otherwise stable reasonable amounts of lithium sourced from spodumene should not make it unstable.

I use zinc in my functional glazes on occasion. Again the zinc base we have in the book has been leach tested and leaching was minimal.

Notice I did not use the term "food safe" in the above paragraphs. I have no idea what that term means as we explain in detail in the book. So far as I am concerned it only has meaning in the legal sense with respect to lead and cadmium where the FDA (and its equivalent in other countries) have set specific limits.

Regards,

John

On Aug 12, 2013, at 12:54 PM, The Fuzzy Chef <fu...@fuzzychef.org> wrote:

> A lot of Cone 6 Glaze recipes contain minor amounts of Zinc Oxide and/or
> Lithium Carbonate as fluxes. Both of these metals are toxic, however,
> and MC6G doesn't think much of them food-safety-wise. However, I'd like
> to get some additional opinions:

What is the meaning of life?
"All evidence to date suggests it is chocolate." Siri

[Robert Harris]

Josh - Zinc metal when fumed can cause problems (metal fume fever), but
Zinc compounds are not toxic in the ordinary way we think. Indeed it is
often used as a supplement to ward off viruses (it stops them binding to
cell walls).

Not to mention that the stuff we use in the studio, Zinc oxide, is the
major constituent in many sun creams - which we smear all over ourselves
(and approved by the FDA)! Indeed zinc was first identified as a suitable
glaze flux in order to replace lead (for toxicity reasons) in the 18th/19th
century - see Bristol Glazes.

Lithium on the other hand can be problematic, especially for people already
taking it for various psychiatric disorders.

I use up to 4% zinc in quite a few glazes. No real problems with them. Most
of the recipes containing zinc are from Europe where there were no
good/cheap/insoluble sources of Boron. Even now Boron as a flux is more
expensive (per unit fluxing power), on the other side of the Atlantic.


Robert

--
----------------------------------------------------

[The Fuzzy Chef]

On 08/12/2013 10:35 AM, Robert Harris wrote:
> Josh - Zinc metal when fumed can cause problems (metal fume fever), but
> Zinc compounds are not toxic in the ordinary way we think. Indeed it is
> often used as a supplement to ward off viruses (it stops them binding to
> cell walls).

Oh, right. I was thinking of Zinc metal, which is an issue when
certifying food service. Pure zinc metal and high-zinc compounds will
leach into food.

> I use up to 4% zinc in quite a few glazes. No real problems with them. Most
> of the recipes containing zinc are from Europe where there were no
> good/cheap/insoluble sources of Boron. Even now Boron as a flux is more
> expensive (per unit fluxing power), on the other side of the Atlantic.

Yeah, the glaze book I'm looking at was published in the UK. In
addition to price, they authors seem to distrust boron.

On 08/12/2013 10:30 AM, John Hesselberth wrote:
> We don't think much of lithium carbonate because we have seen some
> really strange behavior when it is used at levels above 2% -- like
> shivering and crazing on the same pot. Shivering is something to be
> avoided at all costs on functional work. We have not seen that kind
> of problem with lithium sourced from spodumene. If the glaze is
> otherwise stable reasonable amounts of lithium sourced from spodumene
> should not make it unstable.

Hmmm. Can I substitute equal amounts of spodumene? Or do I need to
decrease Alumina elsewhere? Seems like I would need to ...

[John Hesselberth]

On Aug 12, 2013, at 4:07 PM, The Fuzzy Chef <fu...@fuzzychef.org> wrote:

> Hmmm. Can I substitute equal amounts of spodumene? Or do I need to

> decrease Alumina elsewhere? Seems like I would need to …

Lithium carbonate is 40 wt% lithium. Spodumene is usually 6-8% lithium so it is not a 1:1 substitution. And yes you would have to reduce alumina and silica elsewhere. A simple problem with glaze calculation software.

John

John Hesselberth
http://www.masteringglazes.com
http://www.frogpondpottery.com

[Robert Harris]

On Mon, Aug 12, 2013 at 8:07 PM, The Fuzzy Chef <fu...@fuzzychef.org> wrote:

> On 08/12/2013 10:35 AM, Robert Harris wrote:
> > Josh - Zinc metal when fumed can cause problems (metal fume fever), but
> > Zinc compounds are not toxic in the ordinary way we think. Indeed it is
> > often used as a supplement to ward off viruses (it stops them binding to
> > cell walls).
>
> Oh, right. I was thinking of Zinc metal, which is an issue when
> certifying food service. Pure zinc metal and high-zinc compounds will
> leach into food.
>
>

This is a problem only because, as John says "we're not in the business of
providing supplements" ... Since highly soluble zinc chloride is used in
some anti-bacterial mouthwashes, while you shouldn't be drinking grams of
it, it's unlikely to do you any harm. And in terms of stability within the
glass matrix, I think that if your glaze leaches zinc you have far bigger
problems.

> Hmmm. Can I substitute equal amounts of spodumene? Or do I need to
> decrease Alumina elsewhere? Seems like I would need to ...
>
>

Spodumene is basically a lithium containing feldspar. (Theoretical formula
Li2O.Al2O3.4SiO2).

So you basically need to do a proper calculation to replace LiCO3 with
spodumene. Or you could do a line blend reducing your clay.

Robert

[Edouard Bastarache]

Hey "Fuzzy was he" and the gang, check out the english versions of our
repôrts (Smart and I)

http://smart2000.pagesperso-orange.fr/lithium_ceramique.htm
http://smart2000.pagesperso-orange.fr/lithium_ceramique.htm

Plejkore,

Edouard Bastarache
Spertesperantisto

Sorel-Tracy
Quebec

http://www.youtube.com/watch?v=RoTIX39bbxw
http://www.flickr.com/photos/30058682@N00/
http://glazeblogs.blogspot.ca/
http://bookslivreslibroj.blogspot.ca/
http://ceramique-cristaux.voila.net/

[The Fuzzy Chef]

On 08/12/2013 02:09 PM, Edouard Bastarache wrote:
> Hey "Fuzzy was he" and the gang, check out the english versions of our
> repôrts (Smart and I)
>
> http://smart2000.pagesperso-orange.fr/lithium_ceramique.htm
> http://smart2000.pagesperso-orange.fr/lithium_ceramique.htm

Thanks. I don't see anything there about measuring leaching of lithium
from common glazes though?

--
--Josh "Fuzzy Chef" Berkus
blog: http://www.fuzzychef.org
pics: http://fuzzychef.smugmug.com
ClayArt: http://www.ceramicist.org

[Edouard Bastarache]

"Thanks. I don't see anything there about measuring leaching of lithium
from common glazes though?

Fuzzy"

You dont have to.

Plejkore,

Edouard Bastarache
Spertesperantisto

Sorel-Tracy
Quebec

http://www.youtube.com/watch?v=RoTIX39bbxw
http://www.flickr.com/photos/30058682@N00/
http://glazeblogs.blogspot.ca/
http://bookslivreslibroj.blogspot.ca/
http://ceramique-cristaux.voila.net/

[ron...@ca.inter.net]

Hi Ed,

Thanks for posting all that data - but - does your comment mean you
don't think it matters how much lithium leaches into food?

RR

[Johanna San Inocencio]

Thank you for clarifying that, John. I like some of the color responses lithium gives in glazes, but have been hesitant to use it. Do you recommend a limit on spodumene because of its lithium content, or simply view it as a feldspathic flux option ?
Johanna

On Aug 12, 2013, at 12:30 PM, John Hesselberth <jjhess...@GMAIL.COM> wrote:

> Hi Josh,
>
> We don't think much of lithium carbonate because we have seen some really strange behavior when it is used at levels above 2% -- like shivering and crazing on the same pot. Shivering is something to be avoided at all costs on functional work. We have not seen that kind of problem with lithium sourced from spodumene. If the glaze is otherwise stable reasonable amounts of lithium sourced from spodumene should not make it unstable.
>
> I use zinc in my functional glazes on occasion. Again the zinc base we have in the book has been leach tested and leaching was minimal.
>
> Notice I did not use the term "food safe" in the above paragraphs. I have no idea what that term means as we explain in detail in the book. So far as I am concerned it only has meaning in the legal sense with respect to lead and cadmium where the FDA (and its equivalent in other countries) have set specific limits.
>
> Regards,
>
> John
>

[Johanna San Inocencio]

so to get the equivalent amount of lithium in 2% lithium carbonate, you would need to use 20-26% spodumene when adjusting a glaze recipe, correct?
Johanna

[Edouard Bastarache]

Hello,
I read somewhere (Richard Zakin, Describ9) that the limit was 35% for
Spodumene and 5% for Lithium Carbonate.

Plej kore,

Edouard Bastarache
Spertesperantisto

Sorel-Tracy
Quebec

http://glazeblogs.blogspot.ca/
http://bookslivreslibroj.blogspot.ca/
http://bastarachemuseum.blogspot.ca/
http://ceramique-cristaux.voila.net/

[John Hesselberth]

Hi Johanna,

I think it would be closer to 10-14% spodumene.

But to answer your other post, I think spod can be treated as a feldspar as long as you keep a close eye on CTE and don't get into shivering. Remember that lithium is a low expansion material. So are the alumina and silica that are in the spod. So adjusting out an equivalent amount of those would be a first step. You might have to go farther depending on what the starting recipe was like.

Regards, John

Mastering Cone 6 Glazes is now available as an eBook. Check it out at:
https://itunes.apple.com/us/book/mastering-cone-6-glazes/id573583135?mt=11

[ron...@ca.inter.net]

The lithium carb problem that John is referring to has to do with the
amount of solubility (the most soluble of all the carbonates we use).
David Hewitt and I did some experiments to try and find out what was
happening that resulted in crazing AND shivering glazes on some clay
bodies.

We never did find out what was happening but David concluded that
using no more than 2% Lithium Carb in a glaze would be prudent.

There is no solubility problem with Petalite or spodumene.

RR

Ron Roy
ron...@ca.inter.net

Mastering Cone 6 Glazes now available in black and white version -
http://www.thebookpatch.com/BookStoreDetails.aspx?BookID=21563&ID=d2bea83c-2c34-4ed0-8a00-a6f12113515d
or
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Mastering Cone 6 Glazes is now available as an eBook readable on ipads
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[ron...@ca.inter.net]

I just did the substitution in a glaze I made up - 2% lithium carb can
be replaced with about 10.5 spodumene or 20 petalite keeping in mind
that both alumina and silica have to be adjusted down because of the
extra amounts in both spodumene and petalite. Petalite has only about
4.3 % lithium but spodumene has over 7 usually so it would be the
material of choice.

Happy to do the conversion for you Johanna, just send me the recipe.

RR

Quoting Johanna San Inocencio <johan...@frontiernet.net>:

Ron Roy
ron...@ca.inter.net

Mastering Cone 6 Glazes now available in black and white version -
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_______________________________________________

[douglas fur]

Minna
What really impressed me years ago was a photo of a bottle in David Green's
glaze book.
On one side the pot was glazed with a glaze mixed form regular glaze
materials, feldspar etc.
On the other side a glaze mixed to the same formula but using straight
Alumina, silica etc
The first side was a clear shiny glaze. The second was shiny matte, not as
well melted.
It clearly showed the synergistic effect of introducing elements that are
in minerals and frits such as sourcing lithium from spodumene.

DRB
Seola Creek

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[ivor and olive lewis]

Dear douglas fur,.
So what were the other chemical compounds in the reflective Matte
substitute.
Regards,
Ivor Lewis,
REDHILL,
South Australia

[Amy Romaniec]

clay body nuts,
I recently dug ^ 6-10 clay from an old pit, newly reopened , I would like to add grog to make a sculpture clay that stands up better...It is light colored and fires wonderfully in the salt kiln. As I process it slipping , screening, etc what percent of grog should I /could I add for sculpture/ hand building .?
It is quite dry and crumbly out of the ground .easy to get a dry weight.
Are there different types of grog? I mean I would like to retain the lighter color body for the salt.
Is there a percentage of grog that is too much?
Also I will try throwing this clay . I am used to 'store bought standard 119 " which stands up nicely when thrown and sculpted. LOL.
I need a starting point percentage.With the amount of clay available I could make some big stuff if I can get the grog thing right!
Thanks for your thoughts.
Amy
highhorsefarm.com

[douglas fur]

Ivor
The sad truth is I loaned out my copy of Green's book and can't look it up.
Understanding Pottery Glazes had a nice concept, geology to glazes in
100pg.s. It also included thorough instructions for the slide rule which
gives an idea of it's datedness...

DRB
Seola Creek
On Aug 17, 2013 4:44 AM, "ivor and olive lewis" <ian...@westnet.com.au>
wrote:

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[ron...@ca.inter.net]

Hi Amy,

For sculpture you can add 10% (dry weight) easily - more if you are
working thicker - depending on how much texture you want you can use
mesh sizes from 20M up to 50 mesh (20 m is bigger then 50 mesh - 30
mesh is a good size and can be used for throwing as well.

Tuckers has found that Mulcoa makes a very reliable grog.

http://digitalfire.com/4sight/material/mulcoa_70_mullite_1053.html?logout=yes

Some salt firers prefer silica sand but it's getting hard to find some
mesh sizes - you could try some 80 to 120 mesh if you can find it. Be
careful - sometimes silica is mostly fines now and that can lead to
problems.

Let me know if you need more.

RR

Ron Roy
ron...@ca.inter.net

Mastering Cone 6 Glazes now available in black and white version -

http://www.thebookpatch.com/BookStoreDetails.aspx?BookID=21563&ID=d2bea83c-2c34-4ed0-8a00-a6f12113515d
or

http://www.masteringglazes.com/buy-mastering-cone-6-glazes.html

Mastering Cone 6 Glazes is now available as an eBook readable on ipads
and iphones and soom on Macs. Check it out at:

https://itunes.apple.com/us/book/mastering-cone-6-glazes/id573583135?mt=11

[Robert Harris]

I've got Green's book.

The "melted" recipe he uses is

Felspar 26.7
Dolomite 4.4
Whiting 14.3
China Clay 18.6

for which he gives a "percentage by weight of oxides present",

K2O 5.1%
MgO 1.1%
CaO 10.5%
Al2O3 13.7%
SiO2 69.6%

At no point does he say precisely what compounds he used for the latter,
but if we assume he used Calcium and Mganesium Carbonates (adjusted
appropriately), and Sodium Hydroxide (or Carbonate), Alumina and Silica,
this seems a fairly easy recipe to make the sort of comparison we're
talking about.

In the Black and White photo, there is as DRB says, a distinct sheen on the
left had side, compared to a matt gritty look on the right hand side.

Hope that's useful,

Robert

--
----------------------------------------------------

[Robert Harris]

Just as a follow up thought, I suppose you could argue that it's not as
well fluxed because the soluble soda "disapears" into the body. But I'm not
sure how measurable this effect is. And lets face it, there are definitely
plenty of potters that flux with soda ash/potash (the unwashed ash mavens
and shino experts spring to mind).

[Snail Scott]

On Aug 17, 2013, at 8:33 AM, Amy Romaniec wrote:
> ...I would like to add grog to make a sculpture clay that stands up better...what percent of grog should I /could I add for sculpture/ hand building .?

I like 30% by weight, but that's a bit much for most folks. It's
easy to do up 5# batches of clay and just get a feel for each
variation. Start with 10% and 20%, then you can fine-tune it
as you decide what's best for your particular work.

>
> Are there different types of grog?

Many, many kinds. My favorite is actually crushed firebrick
grog, as it is very irregular and I like the yellowish color, but
it's hard to buy anymore, at least around here, and I'm not
inclined to make my own. Silicaceous grog is a lot more
expensive, but strictly graded for size and formulation - a
plus for most folks. It is usually greyish-white. The classic
approach to adding grog is to use a range of sizes from
fine to coarse, which makes for a more workable result.
How coarse is 'coarse' depends on your own tastes.

>
> Is there a percentage of grog that is too much?

Nope. There is, however, a point when it is too much (either
in coarseness or quantity) for you personally. Above 50%,
the clay body can get awfully short and crumbly, though.


> Also I will try throwing this clay...

Ohhhh... Better keep the grog fine, then, and under 15%.
Remember, though, that the more grog, the easier to is to get
large, but the harder it is to throw, as you will lose plasticity.
Personally, I woudl avoid trying to throw and build large with
the same body, but that's me. It can be done, but the more
plastic the clay, the more careful and deliberate you need to
be when building large, as it won't support its own weight as
readily without warping.

-Snail

[ivor and olive lewis]

Robert,
Thanks for the additional information.The notion of soluble ingredients
crossed my mind.
I have noticed that the further I depart from natural minerals as
ingredients and the grreater the refinement of the substitutes the greater
the refractoriness of the substitute recipe.
Talc, Wollastonite, Annorthite (If a supplier can be found.) Petalite,
Spodumene, Cryolite and the felspar family members are, in my opinion,
preferable ingredients. Better to disregard raw or refined Oxides and
Carbonates.

Regards,
Ivor Lewis,
REDHILL,
South Australia

[ivor and olive lewis]

Dear Amy Romaniec
You say nothing about the plastic nature of your new clay source except that
" It is quite dry and cerumbly out of the ground....." This suggests to me
that the clay fraction of the raw material is relatively low. In such
circumstances it might be prudent to add a proportion of Ball Clay to
enhance the plastic strength and limit the proportion of grog unless your
work demands a rough surface.
I would like to know about the plasticity of your find.

Regards,
Ivor Lewis,
REDHILL,
South Australia

[Amy Romaniec]

Ivor Lewis.
re new clay find
the clay is bluish grey and very slippery , and very pure, no pebbles., reminds me of porcelain. I made a pot on site using a 5 gallon bucket as a "wheel" head . this was fun but I had to make a cooling tower shape to get it to stand up. the pot base is 5" across and it is 12 " tall.walls about 1/2 thick I kept turning it in the sun and adding 2" ropes of clay. These were dug from an exposed clay puddle on top of the seam of clay..(deer tracks and all)
It was hoot making a pot on top the whole undug seam of clay
would have been neater to dig a pit
and fire on sit e too. The owners plan is to reopen the seam . from what I understand it is 80 ft deep by core samples he had taken. It is an old surface mine that fell into dis use except for the horseshoe pitching folks that get their "clay" for their pits there.
I think it would be way cool the have a gathering of clay folks on site and make a kiln , process some clay and fire a way, you know music, food and the whole works.
kindo like a sheep to shall gathering! LOL I am not an organizer though, cannot even organize my self Ha HA
here I am totally off subject. the guy will sell truck loads to folks who come , maybe if it gets reopened there will be equipment there to load a truck. He was using a newholland front loader. difficult to dig with, but loaded well.
we have put this clay in a salt kiln w/out any additives and it is beautiful firing to ^10 it vitrifies at ^ 6.
I do not try lots of clay so I cannot judge the plasticity.I just know that it did not stand up like the 119 I am used to and hope d to fix it with the grog.. I think it was crumbly caus it was dry and not exposed to water . in the puddle it was slimy.like porcelin slip. it leaves your hand silky with powder after wedging.
I do have ky ball clay for glaze mixing so I could try some of that. if it will not throw.
I Just know there is Sooooooooo much clay there that Maybe i could make some BIG stuff. LOL
thank you for your input. as I have no mixer or pug mill it is a hands on for me.

[ivor and olive lewis]

Dear Amy,
Do the owners of this find have any documentation relating to the mineralogy
of their treasure trove ?
You might wish to read Frank Hamer, " The potters dictionary of materials
and techniques" ISBN 0-8230-4210-3. The entry on Workability illustrates a
simple bending test that can be used to judge the usefulness of a native or
any other type of clay.
About thirty years ago, one of my year 10 students brought me a sample of
clay from the base of their sand quarry. He learned to process it and
produced what seemed to be a good plastic clay. . However, when the thrown
test pieces were dried they all shrank and cracked. My explanation was that
this native clay contained a mineral called Halloysite. This has a similar
composition to Kaolinite but the crystals are not flat sheets but tubular.
This has a profound effect on the qualities of a clay
Best regards,

[Amy Romaniec]

Ivor,
A geologist friend is working with the owner to take samples and help him market his clay. they are thinking tiles..
I am on the fringe feeling LUCKY to be able to dip my shovel in before it is turned into a working mine.again.One can see the huge, long , now woods covered cut along the side of the hill of the former dig.. It is a very beautiful woodsy setting ,kind of on top of a mountain . the owner has enjoyed this for years ,keeping a nice gravel road with wide mowed set back s,.as the entrance to his secluded property. His unemployment now has him wanting to market the clay.
The geologist is also a clay sculptor and I hope has not steered me wrong in thinking I could make stuff out of this clay ..as he has tested it in the salt kiln with nice results.
I just secured the clay this past Thursday . so today I will add some grog that I have on hand in different percents and ball clay and see what happens..I do not know ifit has been thrown raw. so I will test that too.
I tried a little rope of clay around my finger and it did have little stresses but did not totally break. I really have no reference point though, because I have not tried this with my regular body . so many tests to perform I feel like a beginner I will look up workability of clay .
Hoping to make a big tang dynasty style horse. build a kiln around it and fire.away.LOL probably a dream!
Thank you for your input --has me thinking , which is good !!!
Amy Romaniec
highhorsefarm.com

[ivor and olive lewis]

Thanks for your note Amy.
I'm pleased to learn that you are getting good results with this clay in a
Salt Firing. This process is one that I engaged in over a considerable time.
Through my contacts I was able to get clay and have work salt fired for
students in the class I attended in the mid 1960's. That clay was the from
beneath Tyneside coal seams. I would be pleased to learn what your geologist
friend has to say about the mineralogy of this clay.
Sincerely,
Ivor





fired----- Original Message -----

From: "Amy Romaniec" <highho...@hotmail.com>
To: "New ClayArt Mailing List" <cla...@ceramicist.org>

Sent: Monday, August 19, 2013 10:34 PM

[Lee Taylor]

Dear Amy,

I have had great results with local clays at cone 10. My recipes blend dry
clay in quantities suitable for improving the workability or refractory
qualities of the local clay. I have yet to find one that is good enough by
itself. My work is wheel made, so the plasticity is pretty important. I
like to make clay bodies in parts of six to eight, by weight. One part is
always feldspar, so this makes it around 12 to 16 percent feldspar (which I
think is a lot). I also like to add anywhere from two to five percent of 35
mesh grog, two percent bentonite and two percent kyanite to the mix.

So a typical recipe would look like:

2 parts local clay (or three or four parts)
1 part missouri fire clay (or other refractory clay-maybe kaolin)
1 part om4 (or not)
1 part foundry hill crème
1 part feldspar (usually custer)

Plus: 2% Bentonite
2% 35 mesh Grog
2% 35 mesh Kyanite

I find that firing a test of the local clay to cone 10 first will give you
the refractory qualities, so you will know how much other stuff is necessary
to make it work. I am told there are great clays to be found right out of
the ground. Certainly there are plenty of historical accounts of such.
Though, I have yet to find one.

It is also worth the cost of a chemical analysis of the local clay, so that
you can compare it to known clays and better formulate the final recipes.

Your description of the "cooling tower" effect sounds like it may have a
quality similar to one of my local clays. I think one of mine is
"thixotropic" which means that it goes from stiff to mush with just a few
drops more water. Ivor and Ron can help explain this chemically. Though,
my clay works fine once you get enough other clay materials mixed in with
it.

Several test recipes fired to the desired temperature, followed by the
"flick and break" test will give additional insight. I flick the fired clay
test bars with my fingernail to see how it rings (a crude vitrification
test) and then break a bar to see how strong it is. Of course, there are
many more scientific test that can be performed. Though, these rudimentary
ones have proven good enough for my purposes so far.

Local clay is a rewarding endeavor! Try 1 part (by weight) local clay and 1
part wood ash (washed or unwashed) and see what you get as a glaze. Often
this turns out to be a nice celadon. I am interested to know what makes
your clay the bluish color you describe.

Please keep us posted.

Happy prospecting!!!

Lee R. Taylor
Buffalo Creek Pottery
Lexington, Virginia

[Amy Romaniec]

Dear Lee, and all,
I wet 10 # of dry clay to sieve it . hoping to add 20 % grog on hand. ooops should have only wet 8 pounds so I could add 2 # of the grog.to make the 20% ratio.
I feel like I am in kindergarten. LOL I am poor at ratios
The wet clay hardly needs sieved it is so clean. kind of weird.like yogert.
I did notice while making the "cooling tower"that ,like you said ,a few drops of water caused it to melt.
I will persevere
thinking of all the sculpture and pots I want to make. settling for getting more buckets to weigh out clay with the proper ratios. yikes this is tough on my old brain , but I have a ton of this neat clay
thanks a million for all the input!
Amy,
Highhorsefarm.com

[douglas fur]

Lee

" I am told there are great clays to be found right out of the ground.
Certainly there are plenty of historical accounts of such."

I've found two clays like this. I thought "Oh man. I really want to make
pots with this". In both situations I was told "the owner is very
particular and you won't be able to get any out of him..."
I've been doing a lot of clay research online recently. It's amazing how
you can get from 1946 paper on the feasibility of extracting Aluminum from
red clays or to an aerial photo where you can zoom in on a local
brickyard's clay pit clear enough to see the wheels on their front end
loader.

on a whim I googled Clay mineral resources and came up with-

http://dmme.virginia.gov/DGMR/pdf/vamin/VAMIN_VOL28_NO01.PDF
Which included the phrase-

*Residual and transported clay, shale, phyllite and
schists are used as raw material to produce bricks and
clay dummies in Virginia.*

"*clay dummies" *are they talking about us? should I be offended?

DRB
Seola Creek