Pit Fire

[loafskibum]

I am going to play around with pit firing with saw dust. Has anyone had any luck with this without first firing it in an elec. kiln? Any ideas or tips would help! Thanks.

[doodle50]

I am going to play around with pit firing with saw dust. Has anyone had any luck with this without first firing it in an elec. kiln? Any ideas or tips would help! Thanks.

 

 

Try it and see! I think that you'll want to fire them first or the 'attrition rate' will be very high.

see this...

http://www.hknot.com/gallery/pitfire.html

[Isculpt]

I am going to play around with pit firing with saw dust. Has anyone had any luck with this without first firing it in an elec. kiln? Any ideas or tips would help! Thanks.

 

 

A local Native American tribe has been doing a variant of this for, according to archeologists & historians, 2500 years. Prior to the advent of electric stoves, pots were heated in fireplaces or open fires. Nowdays the pots are pre-heated in an electric stove, starting pots at the stove's lowest setting and then slowly (over a period of 4 or 5 hours) raising the temperature to 500 degrees. When pots have been held at that temperature for at least an hour, they are carried to an outdoor fire built on the ground (not in a pit) that has burned down to coals. The larger coals are raked to the outer edges of the fire circle and the pots are placed in the smaller coals and then covered with branches or slender pieces of wood that almost immediately catch fire atop the pots. After this fire has burned down somewhat, any unburnt branches are carefully removed so that pots can be covered with a material that will produce smoke, such as pine bark. The pots are removed from this last firing while the pine bark is still smoking (in order to preserve some unsmoked areas on the pots). In such a firing, breakage and cracking can claim all the pots -- or none of them. I've seen ten coil-built pots fired this way with no breakage or cracking in any of them, but I've also seen an 80% loss in this type of firing. In my somewhat limited experience the typical loss is around 25%, with a long drying period prior to firing being a major factor in loss prevention.

 

I have done roughly the same thing with sawdust by preheating the clay pieces in a stove, and then placing them on a layer of bricks covered by sawdust in a metal trash can which has been drilled with a 1/4" drill bit every 12 inches or so. I add sawdust as I layer the (in my case) clay sculptures, topping it all off with a 6" layer of sawdust. I add crumpled newspapers to the top, light the papers, cover 90% of the opening with the trash can lid, and leave it until the smoking has ceased and the sculptures are cooled. With this technique I have experienced cracking in 25% of the sculptures, with occasional breakage due to poor stacking in the trash can. To address the breakage problem, I'm planning to experiment with circles of screen wire propped on perimeter bricks between the pottery layers to prevent one layer falling onto another as the sawdust burns away.

 

Hope this helps....

[karstyl]

I just found this forum searching for a different pottery related topic, but found this thread to reply to.

 

I have done a barrel fire. We had some pieces in it that were bisque fired, and they all made it without chipping, we also had some that went in green and the results were more mixed. The most common loss was at attachment points, if a decoration was not well applied it came off, but those that were well-attached made it through just fine. The second type of loss was during the firing. This only happened with the pots that were on the side of the barrel and did not get fully fired or that might have had uneven heat applied to them. The third type was those that broke with unloading, and they were very incompletely fired and very fragile.

 

I think if I was able to use a pit instead of a barrel (limitation of the site we were doing it at) it would have worked better, there would have been more insulation. It was also a windy day so the heat being blown away from the sides of the barrel. We did make sure the greenware was very dry before putting it in, the pieces that we were unsure of we cooked in a regular oven, bringing up the temperature slowly to around 300 then turning it off and leaving the door closed so it cooled slowly. If we had another week to let them dry I think that this step would not have been necessary, but we only had one and a half weeks between the building day and the firing day. The stuff I made before the firing day I did not dry in the oven.

 

The fuel was a mix of wood, cardboard and wood shavings.

 

Here are some pictures, of the barrel on fire, a broad pic of everything being unloaded, and more detailed pics of the stuff I made. The first few have before and after pics as well:

http://hrefna.karsty...ed_Pottery.html

[hansen]

I am going to play around with pit firing with saw dust. Has anyone had any luck with this without first firing it in an elec. kiln? Any ideas or tips would help! Thanks.

 

 

yeah, form the pieces so they shrink uniformly, for example, a sphere or semi sphere: check the designs of pueblo pottery. Remember to use clay with grog or other appropriate thermal shock design such as raku clay. Paint the terra sigalatta over this for burnished surfaces, etc. And take your time with the firing.

h a n s e n

 

 

 

[Marcia Selsor]

I am going to play around with pit firing with saw dust. Has anyone had any luck with this without first firing it in an elec. kiln? Any ideas or tips would help! Thanks.

 

when teaching primitive firing techniques and firing local clay using a pit (in the ground hole) I did the following:

1. dig a hole about 2-3 ft deep.

2. cut an edge about half way up the wall that will support a grate or square BBQ grill. Can use more than one grill in a longer hole.

3. start a wood fire in the lower part of the hole, letting good coals accumulate.

4. place the grate on the ledge.

5. let the pots absorb the heat from the blazing fire.

6. place the pots upside down on the grate.

7. cover with well dried cow pies to a height at least 1-1.5 ft. above ground level.

8. Let it smolder. You can use sheet metal to seal off wind for better blacks.

9. AFter a few hours, flames will burst to the surface.

10. Let it cool and unload.

[Marcia Selsor]

I am going to play around with pit firing with saw dust. Has anyone had any luck with this without first firing it in an elec. kiln? Any ideas or tips would help! Thanks.

 

 

When firing a barrel with sawdust, I have always fired bisque ware. This firing system is fairly quick and may be too quick for non-bisqued pieces.

Maybe you could preheat on a bbq before loading the barrel.

For some added fuel, I place newspaper, sticks, charcoal briquets and large sawdust. I am respectful of fine sawdust after witnessing spontaneous combustion when fine sawdust blows into the air.

You can play around with additives, the most common being salt and copper carb. or miracle grow.

[Hopscotch2]

For those of you who use pitfiring techniques I have a few beginner questions:

I am interested in trying to make glazed pots in a pitfire because I can't afford an electric kiln and also because I want to experiment with the effects of this method.

Is it possible to aim for bisque firing using a pitfire? I note someone advised placing greenware in a BBQ shell for a period of time would that be sufficient or is that just an attempt to prevent cracking in a longer(higher temperature) pitfire?

What sorts of glazes might be used with wood or charcoal pitfiring? I have only seen a few videos of people using pitfires. The ones I've seen all use various methods to decorate the surface of their ceramics (colour and shapes) for artistic effect. I'm presuming it is possible to have some success with glazes on pots that one wishes to be waterproof?

[oldlady]

welcome to the forum, hopscotch.   where do you live?   i know people who do this kind of firing regularly.  if you are close, you might contact them.  it is not something i am interested in personally, but i attended a series of unusual firing methods on the same day.  maybe you could, too.

[neilestrick]

1 hour ago, Hopscotch2 said:

For those of you who use pitfiring techniques I have a few beginner questions:

I am interested in trying to make glazed pots in a pitfire because I can't afford an electric kiln and also because I want to experiment with the effects of this method.

Is it possible to aim for bisque firing using a pitfire? I note someone advised placing greenware in a BBQ shell for a period of time would that be sufficient or is that just an attempt to prevent cracking in a longer(higher temperature) pitfire?

What sorts of glazes might be used with wood or charcoal pitfiring? I have only seen a few videos of people using pitfires. The ones I've seen all use various methods to decorate the surface of their ceramics (colour and shapes) for artistic effect. I'm presuming it is possible to have some success with glazes on pots that one wishes to be waterproof?

Pit firing and glazes do not go together. The pit won't get that hot, and the combustible material would get stuck to the glaze if it did. Pit fired pieces will remain porous after firing. Pits are also not great for bisque firing because they do not heat slowly or evenly. A BBQ will not get hot enough for bisque, either, but could be used to preheat before going into the pit. Unfortunately, there are limits to what you can do without a kiln. Google 'primitive kiln building' and you'll get some ideas about what you can do with homemade primitive kilns that would allow you to fire hotter. It's not something you can do in a suburban backyard, though, but neither is a pit firing.

[Chilly]

The Great Pottery Throwdown did pit firing this week.  They fired pre-bisqued pots.  Pit firing gives some amazing affects, but not with glaze.

[liambesaw]

Our local pottery guild does a big pitfire at the beach.  Pots are bisqued ahead of time.

[Hopscotch2]

Hello again OldLady. You were kind enough to answer my last question on how the excellence of ceramic art is judged. (I had to make a new account because the forum software wouldn't let me log in again.) I'm in the UK and I realise from the responses of several forum members that they are based in the USA (not everyone is).  I couldn't find the Counts' book in my local library, but found others that I hope will suffice. From the brief information I read on Counts and the photographs of his work, I am prompted to acquire his book when I have funds. I have enrolled on a part-time ceramics course at the local art college which should give me a thorough background in several aspects of ceramics. The four session pottery class I initially took was little more than fashioning clay to make small items and similar to art classes that children take at elementary school. I'm now looking forward to the world of ceramics being revealed in more detail, but I have over three weeks to wait and want to experiment! [Imagine a fist pump emoji]

Hello Nielestrick. Hmm, maybe I haven't used the correct terms? I saw a few video by a YouTube potter who referred to his small brick mound assemblage as a pitfire kiln - on reflection it appears to be a cross between a true pitfire and a wood-burning kiln. I've now seen photos of substantil wood-burning kilns that potters have made and those would be too big for my current needs. I understand that it is possible to make a wood-burning kiln from brick and other materials that might fire pots which are glazed.  Perhaps these have to be a certain size to attain the temperatures required for producing glazed pottery? Ah well... I'm in the process of moving house so my experimentation will be limited this summer.

Thank you very much for the implied safety warning; of course I shall assess the fire risks pertinent to my current situation. If all is good then I plan to build a small, partially submerged brick construction and shall attempt to fire pots glazed or otherwise. I'll document the process and try to report back with failures/successes - nothing ventured, nothing gained! 

Hi Chilly and liambesaw. I don't have a TV and the Pottery Throwdown wouldn't be something I would wish to watch. I've seen a few YouTube videos, but unfortunately they don't give a lot of background explanation. Liam, I take your warning about the pre-bisqued pots, but that's not something that is currently available to me. Basically I want to construct a small, inexpensive kiln which will allow me to fire pots. I may have a few failures, but I reckon I should be able to produce something, eventually. I'll take my cue from experimental archaeologists...

[neilestrick]

1 hour ago, Hopscotch2 said:

Hello Nielestrick. Hmm, maybe I haven't used the correct terms? I saw a few video by a YouTube potter who referred to his small brick mound assemblage as a pitfire kiln - on reflection it appears to be a cross between a true pitfire and a wood-burning kiln.

If it's got any sort of firebox that's separate from the area where the pots sit, then it's not really a pit IMO, but rather a kiln. Possibly primitive, but still a kiln. The nature of a pit is that the pots are sitting in the combustible. You can get pit effects firing in a kiln with saggars and such, and probably do it more efficiently than a true pit.

To use glazes you don't necessarily have to get to high fire temps like a big wood kiln. You can do low fire work with a simple, small, primitive wood burning kiln. You only need to get to about 1950F to make that work.

[Chilly]

Look up a book called backyard kilns.  I found an e-copy some time back, can't remember where, sorry.

I didn't have a TV for 35 years.  Only bought one when the gov decided I needed a licence to watch iPlayer.  Still don't watch live TV, only catch-up.

[Magnolia Mud Research]

2 hours ago, Chilly said:

Look up a book called backyard kilns.  I found an e-copy some time back, can't remember where, sorry.

the book can be found on this webpage:  

https://stevemillsmudslinger.weebly.com/ 

[Hopscotch2]

Ehyup folks! 

Chilly and Magnolia, thanks for the advice about the book which I've now found via Magnolia's link. (Steve Mill's teapots made me smile, they deserve to be surrounded by the most sumptuous afternoon tea.) I'll track down that episode of the GPT just to see if they give any detailed tips on pit-firing.

Neilestrick: Indeed, there are several online references to pit-firing which aren't strictly about fires in earth pits.  At the moment I have three types of DIY kiln designs that I want to try, but when I can find a patch of ground that I am happy to sacrifice to being scorched I will attempt a small pitfire. Thank you for the advice about low firing glazes - I'll research into that. There's so much to explore!!

Given the recent concerns about health and the possibility of some college courses being cancelled this is probably a good time to look into feasibility of DIY kilns...