[ratdog]

hello this is my first post.

and first off i would like to say high and ask that ya ll please under stand i got no grammar and cant spell.



that said
i bean digging holes and got some good looking clay

my process:

dig and dry clay

send it threw my keen impact mill to 40 mesh

slack it into slip and screen again

place slip in canvas bags and hang to dry

pug and throw

well i bean getting lots o cracks and hope the shell will help wit it

but what will it do to vert temps increase suspect but not shore

and what else can happen with the oyster shell i cant foresee.



thanks in advance

happy pots to ya ll:D

[neilestrick]

I think we need more information. How hot are you firing? What color is the clay? Are you running the slip through the 40 mesh again, or finer? What is the particle size of the oyster shell?

I would be leery of adding oyster shell, because it is primarily calcium. It will either lower the melting point of your clay or cause worse problems than that. It depends on the particle size of the shell and the temperature you're firing to. I would add silica sand or grog if you're looking to get some texture into the clay to reduce shrinkage and cracking. You may also need to cut it with some other clay to improve its workability. Few clays work well on their own, which is why we usually blend them to get a body with good workability.

[ratdog]

thanks man

i feel u on the adding other clays but its not an option for me.



k will go to 04 to start but have not gotten the vert temp yet pots are drying now.
i screen clay to 40 as slip and around 30 as dry powder.

and yess I'm looking to stop cracking and shrink without grog but instead oyster clam and other beach shells screened to 80



i will take pics of clay asap and post its dark brown wet and brown with a red tent dry.....i dried a few disks from purger.



its cracking on the first three pots so I'm drying slow now with ice chest.

please help i Hope to use the shell with this stuff to stop cracks.


oh ya ox elec skutt kiln

[ratdog]

pics

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[TJR]

I agree with Neistruck. You have to lose the shells if you want to increase the temperature of the clay. What you are doing is adding calcium carbonate, which lowers the temperature. Try adding another white clay like Goldart or a fireclay like Missouri fireclay.You could also add ball clay . Dry your work slowly under dry cleaner bags. This will help reduce the cracks.
Have you thought of making your clay into a slip glaze , buying some throwing clay and using yours for glazing?
TJR.
HEY, there. I sent my reply before I saw your pics. Your clay looks like chocolate icecream. You definitely need more tooth, but shells are not it. Where are you located?
T.

[ratdog]

im well south of u t

an no non local aditives

so u say no shell what about sand

[ratdog]

what about this

fire clay pots to 06 cross fingers i have no hump molds on my shelves and then impact mill dim pots to 80 mesh an add to new clay

[TJR]

You can add grog, which is ground up bisque pots. You are using the same clay, so this is not going to raise the firing temperature of your body. I bisque to cone 07. You could hammermill your bisque, sieve the dust out, [and eliminate it]. You could sieve at 40 mesh or greater-20 or 30, and it would probably work. Are you only interested in terracotta firing?
Also, I don't know what u t means. Utah? I am from Canada.
TJR.
If we knew where you are located, someone could help you out with a source of ceramic materials if that is what you want. If you are going for the purist low-tech idea, then you are already there. It's not really clear in your post as to what you are trying to achieve, but I'm always the guy to talk the plane down after the pilot has a heart attack-metaphorically speaking.
TJR.
Now I see that you are in Louisiana. The plot thickens. I still don't know what u t means.

[ratdog]

lol roll on floor

way south of you T.



lol:o


thanks yall

will post if piolt dies an granny wants to fly

[justanassembler]

Where in LA are you? I'm in baton rouge, if you're intent on using local materials (maybe you can explain why?) making your own grog is going to likely be your best bet, or possibly experimenting with blending local clays from different veins of clay to create something more homogeneous

[ratdog]

justanassembler, on 01 June 2012 - 10:52 PM, said:

Where in LA are you? I'm in baton rouge, if you're intent on using local materials (maybe you can explain why?) making your own grog is going to likely be your best bet, or possibly experimenting with blending local clays from different veins of clay to create something more homogeneous

That's the project
Got no mo money jus gas so me my shovel an da bato go dig clay.
I'm on da vermillion an hope to see u there some day.
An ya so fare it's a teracotta an a bit quirky but I'm no expert so its truly a project.

Hopping for something from nothing.

Thanks all y'all for the great help. It's hard to get good info now- a-days people are so closed up u can't even pay a compliment to a strangers face without controversy

So thanks again

[Ben]

Cultures over the world have been making pots from locally dug earthenware for centuries. You are in good company!

You have also run into one of the common problems with these clays. They are usually very plastic and have lots of shrinkage upon drying. This is why we add things like shells or grog or sand.

Shells, as mentioned, convert to quicklime if fired too hot and you are definitely firing hot enough for that. I'd also leave them out. American Indians used them but they fired lower than you are.
Sand can be OK but that depends on what type of sand it is chemically speaking. For example, beach sand can be mostly shell pieces and therefore no better than crushed shells. Silica sand would help in raising the firing temp of your clay when compared with shells.
Grog is a great solution if you have it, or can make it. Making grog can be extremely laborious. BUT you have a crusher. That is awesome!!!
One strategy for making grog that might help, use an additive such as sawdust or rice hulls, mixed with slip to make mud pies/slabs/chunks/bricks/blocks/whatever shapes you want. Since you are in LA you may be able to get rice hulls locally. Do not compress these pieces as we want these as weak as possible.
Dry, fire OUTDOORS to a LOW (1300~1500 deg F) with a long, extended hold at 450~550F to burn out the sawdust. If your kiln is inside make a pit fire outdoors. You only want to burn out the organics and pass quartz inversion (that point where clay is no longer clay but has changed into bisque about 1100F)

What results is a pourous, weak mass that is both bisqued but easier to break up into grog. Run that through your mill, sieve through 40, then pour from one container to another about 5 feet below to let the breeze carry off the finest dust (you don't want that.) This grog can be mixed in with your clay in proportions up until the clay starts loosing plasticity. Be aware, the grog is dry and will soak up lotsa water so you may want to start with slip and mix the grog in with that.

Have fun and let us know how it goes!!!

[ratdog]

Ben, on 04 June 2012 - 08:39 AM, said:

Cultures over the world have been making pots from locally dug earthenware for centuries. You are in good company!

You have also run into one of the common problems with these clays. They are usually very plastic and have lots of shrinkage upon drying. This is why we add things like shells or grog or sand.

Shells, as mentioned, convert to quicklime if fired too hot and you are definitely firing hot enough for that. I'd also leave them out. American Indians used them but they fired lower than you are.
Sand can be OK but that depends on what type of sand it is chemically speaking. For example, beach sand can be mostly shell pieces and therefore no better than crushed shells. Silica sand would help in raising the firing temp of your clay when compared with shells.
Grog is a great solution if you have it, or can make it. Making grog can be extremely laborious. BUT you have a crusher. That is awesome!!!
One strategy for making grog that might help, use an additive such as sawdust or rice hulls, mixed with slip to make mud pies/slabs/chunks/bricks/blocks/whatever shapes you want. Since you are in LA you may be able to get rice hulls locally. Do not compress these pieces as we want these as weak as possible.
Dry, fire OUTDOORS to a LOW (1300~1500 deg F) with a long, extended hold at 450~550F to burn out the sawdust. If your kiln is inside make a pit fire outdoors. You only want to burn out the organics and pass quartz inversion (that point where clay is no longer clay but has changed into bisque about 1100F)

What results is a pourous, weak mass that is both bisqued but easier to break up into grog. Run that through your mill, sieve through 40, then pour from one container to another about 5 feet below to let the breeze carry off the finest dust (you don't want that.) This grog can be mixed in with your clay in proportions up until the clay starts loosing plasticity. Be aware, the grog is dry and will soak up lotsa water so you may want to start with slip and mix the grog in with that.

Have fun and let us know how it goes!!!

Thanks guys.

I'm about to fire .....slow dry worked an we will see if I'm firing grog or pots next.

If grog I got more clay to process and will do vids too.

Will be back soon an tanks again

[ratdog]

Hay I got another q
What ph is best for clay?
I know it has some oil in it if I add KOH to turn oil to soap then hcl to ph up were to stop

My guess 5.8-6.2
An if I leave da oil what about jus a good stable number

What number

Thanks

[ratdog]

ratdog, on 07 June 2012 - 07:36 PM, said:

Hay I got another q
What ph is best for clay?
I know it has some oil in it if I add KOH to turn oil to soap then hcl to ph up were to stop

My guess 5.8-6.2
An if I leave da oil what about jus a good stable number

What number

Thanks

does anyone PH the clay ?



Bump

[neoncat]

Ratdog, I routinely add 5% table salt (NaCl) to the water I add to my dried and screened (17-20 mesh is normal for me) calcium-containing native clays. This is not much salt – only about 5 g per 1 pound (454 g) of dry clay (based on 22% added water). I just add salt to whatever water I will have ready to use - excess can later be discarded after you have adjust your clay body consistency. Seawater (3.5 - 4.0% salt on average) was used by North African potters in their calcareous clay bodies to prevent spalling or “lime blow”. The added salt is no problem and enhances vitrification, as well as increasing the crystallization temperature of the calcium oxide (CaO). Most importantly the salt removes the calcium oxide as a reactant in low temperature clay chemistry.

Calcareous clay (calcium-containing clay) has been used in the production of ceramics since 6500 BC (David Kingery and Pamela Vandiver, 1986), and a high CaO content in the bodies characterize ceramics made in the Near East or Central Asia. Calcareous clay has also recently been found (Journal of Archaeological Science 37, 2010) to have been used for making Tang sancai ceramics, a renowned low-fired glazed pottery produced in China at the Liquanfang kiln in Chang’an city during the Tang Dynasty (AD 618–907). Much of the ancient Greek pottery we love was produced from calcareous clay. In North America, the Oneota, who lived in large farming communities in the La Crosse locality of Wisconsin from approximately A.D. 1300 to 1625, are recognized by the characteristic shell-tempered ceramic vessels they produced. The use of shell to decrease the porosity, improve the thermal efficiency and increase the durability of the resulting pottery was considered a technological revolution at the time.

I have fired from Cone 010 to Cone 10 in oxidation and reduction with good results (Paragon electric, gas, pit-fire).
You can see the white remnants of fossil shells in much of my fired work on Flickr:
http://www.flickr.com/photos/neon-cat/
And also many various types of temper I have used. My native clays can look rough or smooth, depending on treatment and firing conditions. They can be glazed or terra sig can be used.
You will find you have a surprising number of creative and rewarding options when working with native clays.
You can learn about your particular types of clay as you work with them. A local geologist from the university or rock & mineral club might help you with that. Or on-line research into clay and soils in your collection area if you are into that.

This is my first forum post. And, I can't help the way I write -- so don't mind me. I started with native clays and materials because they were all I had/have. I try to keep everything as easy as possible to process and make.

Have fun!

Marian
Neon-Cat Ceramics
Fort Worth, TX
http://www.neon-cat....on-cat_ceramics



[/quote]
That's the project
Got no mo money jus gas so me my shovel an da bato go dig clay.
I'm on da vermillion an hope to see u there some day.
An ya so fare it's a teracotta an a bit quirky but I'm no expert so its truly a project.

Hopping for something from nothing.

Thanks all y'all for the great help. It's hard to get good info now- a-days people are so closed up u can't even pay a compliment to a strangers face without controversy

So thanks again
[/quote]

[trina]

Rat dog

I love your posts, I can't even imagine digging my own clay and then trying to figure out how it can be made better. Good for you!

T