Clay Body for Wood firing with added matter

[Hands On]

Hello

I am putting some work into a large wood fired kiln in May for a 4day firing.  I am wanting some help with percentages for clay mixes I shall be making some solid cube like sculptures no bigger than 30cm square,  but need to add some organic matter to make it lighter and give it some interesting texture. I have been told you can use chicken feed popcorn etc but not sure of how much I can get away with?  Also was thinking of a clay mix as follows  does anyone have any comments on this.?   I am only doing one firing so need to get the clay body right to start with. Any help greatly appreciated  Foster from UK

of 25% fireclay  -  20% Ball Clay -  10% HighFire Stoneware clay -   10% China Clay -  25%   Chicken Feed /Popcorn/bird seed - 10% chicken grit Flint 

[Russ]

If youre able to get Georgia kaolin (tile #6) ive found when added to your body will flash orange more reliably than other kaolins. Dont know about the chicken grit. What does it consist of?

[Min]

I would put some spar in the recipe plus some 200 mesh silica. Although, if this is a one time firing and you haven't tested a woodfire body before I would be inclined to purchase a claybody and wedge in your inclusions. I would ask the people firing the kiln which claybody they recommend and if they are okay with you adding decomposed granite or whatever you are thinking of adding that isn't an organic material.

[Hands On]

4 hours ago, Russ said:

If youre able to get Georgia kaolin (tile #6) ive found when added to your body will flash orange more reliably than other kaolins. Dont know about the chicken grit. What does it consist of?

hello I live in the uk so it will be English China Clay. the chicken grit is pure flint so will add texture plus some surprises I hope

 

[Hands On]

3 hours ago, Min said:

I would put some spar in the recipe plus some 200 mesh silica. Although, if this is a one time firing and you haven't tested a woodfire body before I would be inclined to purchase a claybody and wedge in your inclusions. I would ask the people firing the kiln which claybody they recommend and if they are okay with you adding decomposed granite or whatever you are thinking of adding that isn't an organic material.

yes they are happy with me adding granite chips. I do have a clay body I have used at another wood firing but was looking for something different - yes I could add 10% Feldspar and reduce the fire clay

[Rae Reich]

Vermiculite makes a nice inclusion, with flecks of pyrites and burn-out voids. Also is lightweight and clay can take quite a lot of it wedged in. Look for it in garden centers, used to aerate soil. I still have a bag of it saved from when it was used as packing material for Orton cones and wedge it into my cone pads. 

Edited January 5 by Rae Reich
Afterthought

[Biglou13]

Chicken grit is usually inorganic,    I use grit as inclusion additions to my clay.  I would sinter the grit prior to  adding to clay.  It’s longer conversation but it’s  known concept, my attempt to emulate Shigaraki clay.  This addition will not lighten the clay body for that I suggest adding sawdust to clay..  be carefull not to use oyster shell grit!!!!      
 

if you search back I have posted a recipe based on dick Lehman 12d clay, which is a take on a jack Troy recipe.   I have fired this clay from underfired to 13 ish.   If you can’t find it I’ll re post recipes here  tomorrow.  This a well tested proven recipie.   The addition of fire clay makes it even more hardy but changes characteristics.

are you saying this once fire  or will you bisquing yor work.   Be careful with any solid ish large pieces. That they absolutely dry before firing!

edit   can’t find  my old post here .

i slightly modified recipe in pictures below  i changed plasticizer and lizella instead of red art 

Modified 12 D (original)

EPK                                 36.8

Nephaline Syenite  24.5

OM4 Ball Clay          14.3

Silica                               19.1

Bentonite                       5.1

Redart                              2.5

Total102.3

variation add 36  ap green fire clay   brown  and will stand up to higher temp (ap green is no longer available) im told other fireclays will work

 

. 

Edited January 5 by Biglou13
Correction, addition

[Hands On]

thanks and good to see some pictures 

[C.Banks]

10 hours ago, Biglou13 said:

Modified 12 D (original)

EPK                                 36.8

Nephaline Syenite  24.5

OM4 Ball Clay          14.3

Silica                               19.1

Bentonite                       5.1

Redart                              2.5

Total102.3

 

 

I'd be tempted to sub out some/all of the epk for Helmar.

Once fiing a foot thick cubes sounds adventurous. I'm a bit nervous at the best of times so for sure I'd be concerned about the time it takes water to escape.

again, I'm sometimes overly cautious so, for me, the additions of  organic/inorganic grog helps to move water along more than anything else. I would not want to be responsible for 'surprises'  below 100c.

 

Edited January 5 by C.Banks

[Biglou13]

20 minutes ago, C.Banks said:

I'd be tempted to sub out some/all of the epk for Helmar.

Once fiing a foot thick cubes sounds adventurous. I'm a bit nervous at the best of times so for sure I'd be concerned about the time it takes water to escape.

again, I'm sometimes overly cautious so, for me, the additions of  organic/inorganic grog helps to move water along more than anything else. I would not want to be responsible for 'surprises'  below 100c.

 

I’ve used helmer as a flashing slip. I’m sure it would work.  This body is pretty flashy already.  I should try  maybe get super flashy! 
 

[Mark C.]

Helmer works great as a flashing slip so I would just keep it on the outside myself where its seen and it costs more than epk

[C.Banks]

37 minutes ago, Biglou13 said:

I’ve used helmer as a flashing slip. I’m sure it would work.  This body is pretty flashy already.  I should try  maybe get super flashy! 
 

Now that I think on it i remember a version with significant chunks firing well but chewing through a few fish line cutting wires and creating difficulties while trimming .

We were paying significantly less for helmar kaolin back then I imagine.

[Rae Reich]

@Hands On, if you’re going to fire a solid cube that size mixed with other inorganics without demonstrating its explosive propensities, I’d suggest cutting it apart to hollow out and reassembling it, or coring it in several/many places from the bottom. If you want to make a Process Piece to demonstrate firing effects on a solid with inclusions, you really must be certain that it is dry, dry, dry! And possibly isolated from other pieces.

Is there something I don’t understand about your intention?

Edited January 5 by Rae Reich

[Biglou13]

2 hours ago, Rae Reich said:

@Hands On, if you’re going to fire a solid cube that size mixed with other inorganics without demonstrating its explosive propensities, I’d suggest cutting it apart to hollow out and reassembling it, or coring it in several/many places from the bottom. If you want to make a Process Piece to demonstrate firing effects on a solid with inclusions, you really must be certain that it is dry, dry, dry! And possibly isolated from other pieces.

Is there something I don’t understand about your intention?

My interpretation of original post is that  “one firing” means one opportunity to woodfire once.  ……. There is a lot in OP that raise a flag for me., since we don’t have enough info to better assist. Guessing at clay body,  wood fire kiln owner allowing untested clay on shelves in kiln, ….   What kind of kiln?   Solidish pieces? Organic vs inorganic?    I understand there is first time for everyone.   I would suggest to  Hands On to give us more info.   Use clay suggested by kiln owner.  Also experimenting with form bisqued.  Clarify if it is going to be once fired wood fired. Or are you pre bisquimg.   What kind of kiln? What are expected final cone/temperature……   More info please

[Hands On]

15 hours ago, Rae Reich said:

@Hands On, if you’re going to fire a solid cube that size mixed with other inorganics without demonstrating its explosive propensities, I’d suggest cutting it apart to hollow out and reassembling it, or coring it in several/many places from the bottom. If you want to make a Process Piece to demonstrate firing effects on a solid with inclusions, you really must be certain that it is dry, dry, dry! And possibly isolated from other pieces.

Is there something I don’t understand about your intention?

Thankyou everyone - I did a firing in the same kiln 3 years ago which is an anagama kiln - all the clay I used then was pre mixed and I felt a bit soulless - I have spoken to the owner who has suggested starting with a 50/50 mix of Fireclay and Ball Clay then adding the perlite - I was wondering if anyone had any mixes they like for wood firing and what additional organic matter they put in.  Yes I will core out any of the solid areas of clay as much poss but wish to keep the appearance of it looking solid. I have a small old electric kiln which I’ll use for a long slow bisque, Also was thinking if I am worried about it still exploding I might put it in the fire box ? 
I really appreciate all the in put - I live in the UK so our supplies are different. 
foster

[Hands On]

Thankyou everyone - I did a firing in the same kiln 3 years ago which is an anagama kiln - all the clay I used then was pre mixed and I felt a bit soulless - I have spoken to the owner who has suggested starting with a 50/50 mix of Fireclay and Ball Clay then adding the perlite - I was wondering if anyone had any mixes they like for wood firing and what additional organic matter they put in.  Yes I will core out any of the solid areas of clay as much poss but wish to keep the appearance of it looking solid. I have a small old electric kiln which I’ll use for a long slow bisque, Also was thinking if I am worried about it still exploding I might put it in the fire box ? 
I really appreciate all the in put - I live in the UK so our supplies are different. 
foster

[Rae Reich]

With that prep and bisque you probably won’t have to worry about explosions  

[Kelly in AK]

I once made bricks (a couple hundred) using scrap clay, some fireclay, and sawdust. They were used in a cone 10 kiln and performed reasonably well. I put in as much sawdust as I could without losing the ability to form the clay. I later made sculptural pieces with the same mix, mostly by cutting out rough shapes with a wire. Firing it was a smoky mess, must be done outdoors. The sawdust does nice things though. 

[Callie Beller Diesel]

As long as the early segments of the firing go slowly enough through the applicable temperature zones for burnout, you should be ok for sawdust inclusions. If the kiln is a relatively large one, the sheer thermal mass of everything *may* take care of that. Consult with the owner of the kiln to see if they have proportion suggestions. 

Another possibility for inorganic inclusions could be crushed shells, if you have access. They’re calcium, so they’ll leave small white voids that may crumble away in any unglazed dry areas. 

In terms of making flashing slips, look at any “dirty” kaolins you may have access to. If they’ve got titanium or iron impurities, they could do interesting things. 

[neilestrick]

On 1/4/2024 at 8:23 AM, Hands On said:

solid cube like sculptures no bigger than 30cm square

I wouldn't allow anything that thick in my wood kiln, even with organic inclusions. If it blows up you're going to have your shards stuck to everyone else's work. A successful bisque firing for something that thick will take a few days. Do the owner of the kiln know they're that thick? They should be hollowed out, for sure.