Woodfiring Clay Bodies

[sheppard.lin]

Hello again, another wood firing question for those of you with more experience! I'm going to try a few different clay bodies in an wood firing next month. I'm in Ontario, Can - so I'm going to test a porcelain and Tony Clennell's clay body for sure. I've also seen a lot of work with gorgeous deep purple/brown tones. Are there any clay bodies/slips/kiln placement that I might experiment with to get this color? 

 

Thanks, Lindsey

[GEP]

Can you post a photo example of what you mean by deep purple/brown tones?

[fergusonjeff]

It is likely that the color is coming from a flashing slip.  I can get very dark areas (not sure about purple though) with high-iron flashing slips in longer firings.  In this case the particular clay color is not as important.  I do use a couple darker clays (mixed, not commercial) that will get nice dark browns on their own. 

A picture will definitely help.

[sheppard.lin]

@fergusonjeff

@GEP

Yes, a photo is a good idea. I've also emailed the artist for her input as well - but there's usually value in trying different strategies to get a certain outcome. 

Piece by Emma Smith. 
 

[Magnolia Mud Research]

Top of the head speculation:
A natural iron oxide containing clay may also have manganese oxides as well.  Manganese will produce purple color under the right conditions.

LT

[Mark C.]

Laguna clay makes wood and soda clay as well as wood fire B mix. as noted you can just slip coat many bodies so the body is less important .

[GEP]

Agree with @Magnolia Mud Research. Any cone 10 claybody that is dark to begin with is more likely to produce those colors. I’ve made pots that look similar. This was 10 years ago maybe, I think it was Laguna 910 but don’t quote me on that. Look for any cone 10 claybody that will fire on the darker side even without reduction. 

Here’s a photo that a customer recently sent me. The one on the left was made with this dark clay. The second from left is Laguna Soldate 60. It can fire very dark too, but more reddish than purpleish, and sometimes fires to tans and buffs. The two on the right are Highwater Phoenix, which fires from pale to dark.

 

@sheppard.lin, in your example photo there’s also fly ash on the left side of the bowl, which makes a very pretty contrast with the dark clay. That is achieved by placing the pot in the kiln where it will be in the path of ash flying out of the firebox. 

[Callie Beller Diesel]

The purply iron colour you like in the piece in your picture is definitely from a stoneware. Places where the pieces will get more ash exposure are better, but you don't want to put the pieces right on the bag wall or you'll get all the good crusty stuff. 

If it were me, I'd get a box each of Plainsman H440, which is a lovely red/ brown burning stoneware that is a bit too porous for my taste for functional work, and H570, which is a plain, kinda blah white stoneware that matures properly for functional work. Cut and slam the two together in a 25:75 ratio of 570(white):440(red).  You'll improve the maturity of the final body and still have a nice iron bearing clay that looks good in atmospheric firings. You could dust in a bit of red art for bonus points, but it's not necessary. Plainsman is a bad choice for porcelain, but they do refractory stoneware really well.

 

[sheppard.lin]

Thank you all for your advice! I have lots of experimentation to do now!

[neilestrick]

There are endless possibilities. In addition to the clay body, it will also depend on how the kiln is constructed, and how it's fired. I know kilns that tend to give lighter colors, and some that tend to give darker colors.

As for the porcelain, I would put it in areas that won't get as hot, and won't get as blasted by ash. Wood fire folks often go up to cone 12/13, and most commercial porcelains will slump at those temps. But there will probably be some cone 9/10 areas in the back. Also, because of their high silica content, they tend to just go glossy white if they get too much ash and vapor. So again, and more protected area near the back will be better.

[Marcia Selsor]

I personally like to use porcelain in wood firing. I have used several varieties sometimes combined with Shino. I have also used a black clay called Death Valley. Which if very thick tends to dunt.

 

 

[LeeU]

This is Troy procelain/cone 10, fired in an anagama-celedon on the rim and the rest unglazed-just the orange flame color.  The underside just past the orange flash is pure white.

This porcelain box was fired with just a bit of shino on the lid.  The black ash on the right side is striking when you can see the pure white near the bottom of the box. 

 Unglazed porcelain cone 10 woodfire.