Sunday, November 3, 2013

Two natural clays

 When talking with a teaware enthusiastic, I can be pretty sure, some variation of this question is going to pop up: "How natural are your clays"? I can replay that clays are natural by nature. But this answer would not go to the point, would it? Clays can be mixed together and grinded to desired characteristic. Clays can be also enrich by natural as well as more or less artificial additives: river sand, quartz, grog, feldspar, iron scales, saw dust, oxides of different metals or other colorants and so on... the list can be quite long. Clay companies usually creates recipe of new clay by mixing  several clays from several mines/deposits, then grind them to fine, seamless clay, add grog of certain grain size as bones of the clay and other additives, if needed. All is mixed again and "pug-milled" to plactic bags. Such bags are then waiting for potters as we are, ready to use. Or, in order to create our own recipe with special quality we are looking for, can be mixed and adjust again.

This practice have quite a few obvious benefits and most of our clays come to our studio this way (we pay attention to companies we buy from - clay have to be simple, without any artificial colorants or additions). Getting clays this way means less of the hard work, stable clay body and pretty wide range of different clays to work with. But there is few things missing and that is why we keep searching for really natural clays.

1) Clays, which you dig directly from nature are unique and you want that for special pieces. Even from the same deposit clay will vary, if you use clay from different spot or depth.

2) When one use natural clay then it is usually just sieved from too coarse particles. Such clay is not grinded, which means that there are grains of different materials in different sizes, the whole spectrum compare with uniformly grinded manufactured clay with added grog.

3) Using natural clays brings new live to potters life. Getting know a countryside, where clays are resting for thousands years, being close and familiar with material we work with - it all helps to give enegry to final pieces.

During the summer I was happy to meet two new clays, both clean and natural. One was given to me by friendly colleague, second one I found thanks to coincidence, when having a trip with friends, looking for summer swimming.

The yellow clay is more rough, my friend probably have not sieved it at all. The black one is more plastic, greasy like. When I started to make first pieces from those clays I already have a rough idea how they are going to look like. I have seen one piece from the yellow one (fire by my friend) and I make few test cones from the black one.

Both clays are very nice to work with, so nice that I decided to brake my plan. Instead few test cups, I end up with teapots, cups, yunomies and yes, a couple of jars.

You can see even after bisque fire (first firing to 1000°C), the black color disappeared. The original black
color was of organic origin and it burn out.
black clay after 1000°C

Thanks to these two new clays, the kiln opening last week was even more surprising then usually. Both clays work in whole range of temperatures which you can find in our woodkiln. The black one likes rather hotter parts and takes easily nice flame effects there. Some pieces were unglazed, on some of them I tried nuka and shino glazes. Take a look at pictures and you will know: We are already working on two trips to visit two interesting places of Czech countryside. Some barels, hoes and shovels are going to go with us...

yellow clay, shino glaze

black clay, nuka glaze

yellow clay with tenmoku glaze

black clay with white slip and white crackel glaze
rough yellow clay teapot...

bisque fired yellow clay teapot...

...and fired to around 1280°C in charcoal part of our woodkiln

rough black clay

black clay after 1000°C

...and fired to around 1280°C in charcoal part of our woodkiln

Thank you for reading!


  1. Very promising. Thanks for sharing !

    1. Promising indeed. Thanks for stopping by, David.

  2. Love the way both clays turned out.

    Here in my area I've only found a small batch of red earthenware clay. The area is dominated by a very plastic clay called 'Lillebælt ler' which can absorb huge amounts of water and will shrink a lot, when dried.

    I have to experiment more, using the Lillebælt ler as a slip in low fire. I tried to fire a test of the slip along with stoneware and it crawled of the test tile.

    Lots of experiments are waiting to be done.

    1. Thanks!

      Your "Lilebaelt ler" sounds like kind of natural bentonite or other clay with a lot of bentonite in it. You can try to put lighter layer of it before bisque firing and then put glaze on it. After few experiments, you can find very interesting surfaces:)

      Good fire!

  3. Lovely! How are these clays in means of porousness?

    1. Depents on temperature and fire, but the black one (ligher after firing) looks more porouse, especially when sitting in colder places of our kiln.

      Thanks for stopping by Jakub

  4. I am torn between the rough yellow clay teapot and the bisque fired yellow clay teapot and the rough black clay is porous as one mentioned. Perhaps meaning more usable or readied to be used.

    When in high school some decades ago, I did take a pottery class for two semesters (part of art classes that I enjoyed and seem to have done well in them); anyhow, the challenge for me in pottery: is not the molding of the clay by way to help it take shape but what happens once it enters the kiln and left there and over night the teacher remove these things and arranges them for the students to come along and collect their work. It is there that I was presented with challenge; of which was mine and not recognizing it...with exception to caption that it had my name at the bottom of it.

    I am saying many pots I tried to make ended as ashtrays; I should emphasize 'warp ashtrays' with my name (in the bottom) tagging me as creator of this thing that my art teacher would see before her. My art teacher would exclaimed: "how lovely, an ashtray it is and great coloring to...glaze even."

    In my defense, I may have made one pot for the term's duration.