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mrs_christopher

Native American pottery technical question

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Lately I've been fascinated with the Acoma Native American's style of pottery. From what I gathered on their technique is that they make coil pots from their native red clays, but then they cover the pot with a bright white slip before firing.

 

After reading the latest post on CAD the other day, it inspired me to get back into trying red earthenware clays like terra cotta... etc.

 

However, I am having a brain freeze at figuring out how to obtain a nice white slip to go over the piece and resist cracking, or flaking off before firing.

 

Would a white low fire earthenware slip mesh well with the red low fire earthenware clay?

 

Or does anyone have a great universal low fire slip that does well on most low fire clay bodies? Does is even exist?

 

I had seen where a couple potters on this forum dabbled in Native American style pottery, which is why I'm asking. Certainly someone must have an answer. ;)

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post-6532-132095609331_thumb.jpg

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If your white low-fire clay body has a similar absorption rate, shrinkage rate, and firing range to your red low-fire clay body, then there is a strong likelihood they would be compatible. Otherwise, you could have problems with shrinkage, cracking, flaking, etc.

 

Pete Pinnell had a terrific article in the Spring 2011 Clay Times called "A Changing Recipe for Engobe." In the article, which includes white slip recipes, he talks about the importance of fit especially for earthenware due to the relative high absorbancy rates of the clay body at low temperatures.

 

Another good source is Vince Pitelka's website at Tennessee Tech University - Appalachian Center for Crafts. Two papers posted are good: All-Temperature Decorating Slip and Patinas and Glazes.

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I am curious as well and hope you get an anwser. I also did a search for books. Came up with this one and thought it might be a good start book

 

 

 

If your white low-fire clay body has a similar absorption rate, shrinkage rate, and firing range to your red low-fire clay body, then there is a strong likelihood they would be compatible. Otherwise, you could have problems with shrinkage, cracking, flaking, etc.

 

Pete Pinnell had a terrific article in the Spring 2011 Clay Times called "A Changing Recipe for Engobe." In the article, which includes white slip recipes, he talks about the importance of fit especially for earthenware due to the relative high absorbancy rates of the clay body at low temperatures.

 

Another good source is Vince Pitelka's website at Tennessee Tech University - Appalachian Center for Crafts. Two papers posted are good: All-Temperature Decorating Slip and Patinas and Glazes.

 

 

Thanks for the Book suggestion, Buckeye!! I'm happy to see there's someone who may have some of my questions answered. It's hard to find people that write about Acoma and Laguna pottery.

 

Thanks Bciske!! Those are wonderful suggestions and tips! I'll have to check them out!! I know there's commercial engobes out on market, but I'm just not 100% sure if they would work or not.

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Yay! I found an answer. and wanted to share incase anyone else references this thread later on!

 

Taken from http://www.alltribes.info/index.php/Acoma_Pottery

 

A fine white kaolin clay is used to make the white slip of traditional Acoma pottery from a mixture of fine clay and water. The potter brushes on several coats of the white slip, which needs to dry between each coat. After the final coat, the pot is again sanded with a stone. This slip serves as an ideal base for the paints most Acoma potters use. The white backgrounds allow the Acoma potters to create crisp, detailed black images, as well as rich polychrome designs. The Acomas use two types of paints, which are vegetal or mineral based, for their intricate designs. The clays, vegetable binders, and mineral pigments for the distinctive Acoma polychrome are gathered or dug locally and are ground and mixed by the potter to get the intended colors. The pot is then painted with the specially prepared pigments, often with a yucca brush, much as it has been done for hundreds of years. The exact mixtures of binder, water and pigment must be used or the colors will be either too powdery and flake off after firing or be too watery and pale.

 

 

The last step of firing changes and deepens the colors while bonding them permanently to the clay. Traditional Acoma pottery is fired at a very high temperature, which makes the pot stronger. Since the early 1970s, most traditional potters fire their pots in an electric kiln, which can maintain the steady high temperature desired, about 1,873 degrees Fahrenheit / 1,023 degrees Centigrade, a temperature that rarely can be reached in exposed outdoor pit firing.

 

 

 

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You may have to dig a a little deeper for a answer I was part of a Anazai research group, we used a white earthen ware and a white slip and black stain. After the project was over I decided to try red earthenware with the same white slip and black stain, it polished with the rock well but when it fired it flaked in small areas all over. I decided that I would do some testing at a later date. The article you posted is incomplete in it's facts and too general, for instance it mentions sanding the slip with a rock, burnishing is the description and has to be done at the right moisture level of the slip. Keep researching. Denice

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You may have to dig a a little deeper for a answer I was part of a Anazai research group, we used a white earthen ware and a white slip and black stain. After the project was over I decided to try red earthenware with the same white slip and black stain, it polished with the rock well but when it fired it flaked in small areas all over. I decided that I would do some testing at a later date. The article you posted is incomplete in it's facts and too general, for instance it mentions sanding the slip with a rock, burnishing is the description and has to be done at the right moisture level of the slip. Keep researching. Denice

 

 

I guess I just got excited that they mentioned "Kaolin", because it gives me another place to start searching as far as slip recipes. Unfortunately, I am not a chemistry major, nor a ceramics engineer, so my knowledge about the effects of raw materials is very-very minimal. I wish I knew it better to determine whether something would work together, or not! I really envy those who can!!!

 

I may just be forced to use a few coats of a white underglaze until I can get a good white slip recipe that would mesh. I've contacted some suppliers out west to see if they would carry anything compatible, but have not heard back yet.

 

My quest may have to wait till next summer when I get back out there. :\

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I wouldn't suggest using casting slip. It's kind of a different animal, even before you add the deflocculant. They tend to have high shrinkage rates compared to commercial clays that are sold for hand building and wheel work.

 

How historically accurate do you want this to be, and have you mixed anything from dry before? If it doesn't have to be *exact* and you have access to a gram scale, I have a slip recipe that goes on most things in a very user-friendly way and burnishes up nicely. Pm me if you would like it.

 

Anyone who wants it can have the recipe. It was "share ware" from the Alberta College of Art and Design shop.

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I was part of a Anazai research group, we used a white earthen ware and a white slip and black stain._-----

 

Hey Denise,

If you're still interested in Santa Clara pottery, try making a test tile with

white clay, burnish with a red oxide, fire it and out line or highlight with

black shoe polish. It'd be a faux finish but might be worth it if the time

spent was about 20 - 30 minutes. I started one about 7 yrs ago, I guess I could

finish it, and post a picture of it when done. I only mention this, cause

when I started out in this field, one of my interest was the black on white South

western pottery. When I asked the archaeologist about the black pigment used

he said, "why not use black shoe polish?, that's what they use in mexico for the tourist souvenirs!!!.". Can't you tell?, what about the smell? " No you can't

tell and it doesn't smell after it dries!!". I'm somewhat a purest, so for a brief

time I did play with mixtures of honey/sugar and flour hoping to fire the pottery

and dust off the ash leaving the black carbon pigments. There weren't too many areas that I didn't experiment in when I first got started.

The fire science

I had in the fire department explained a lot about firing pottery and the

automotive school air condition classes had heat transfer principles that

applied to pottery also.

 

See ya later,

Alabama

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My Granny, who lived near Salt Lake City until 1910, told me the Indians who sold their wares by the roadside to the tourists in those days coated them with a final gloss of egg white. I poo-poohed this info, as a know-it-all 2nd year student. Now, I think it might be true. Ever know anyone with an egged car? I also learned more recently that in China, at about the same time, dirt floors received several coats of egg white as a sealer so they could be swept.

 

Tiffany, Engobes are fairly easy to make and test, but if you'd rather buy something already mixed, your supplier should be able to point you to the slip or engobe that will fit your clay.

Rae

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I went to an image transfer workshop with the AMACO people in Houston. We used an earthenware slip to pick up the image. The coating for the background was LG  Underglazes. They worked beautifully. Maybe you should talk to your earthenware supplier to recommended what works with the clay they'll be selling to you.

 

 

Marcia

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