sawdust vs. wood firing

[JLPicard]

Hi , new here. I'm using clay from the studio where I practice that fires to cone 6  for bisque for test pieces in a first time sawdust Kiln. I've made my own wood fired kiln that fires 2-3 pieces at a time. that got hot enough to crack the cinder block chimney. the pieces actually came out white and a good sound. I temporarily dismantled it to find chimney sleeve of terracotta and am repurposing the good cinder and pavers and made a pit for sawdust firing. I can probably fit 10 pieces on 2 levels in it. I'm not expecting white but will it fire hard enough to withstand holding non caustic liquids like water Beer, wine? Should I slowly preheat the pieces in the oven or gas grill to avoid the shock of sudden heat that may crack pieces. I am planning to rebuild the wood kiln in the spring with heavier cinder blocks and I hope a better chimney. I'll add a photo or 2 to later.

 

[Bill Kielb]

Pictures would be great. Not sure what your goal is but firing something to bisque temps leaves it porous which means liquid will leach through - pretty much any liquid. Your cone 6 clay at this point is sintered and not melted and actually by design sort of  ideal for absorbing glaze yet being more sturdy than greenware for decorating. Actually, your thread creates many questions for me …….. do you have a pyrometer……..cones, …… use firebrick ……….. maybe a little more descriptive context of what you hope to accomplish in the end would help as well.

[neilestrick]

Cinder blocks are not appropriate or safe to use for a kiln, other than as a base to hold actual kiln bricks. At best the heat will weaken the block, at worst it will spall. Invest in some firebrick, or at the very least use house bricks if you only plan to fire to low fire temps.

Pit firing will not get pieces hot enough to be used for food or drink, or even to melt glaze. It's only good for decorative pieces.

1 hour ago, JLPicard said:

fires to cone 6  for bisque

Do you mean cone 06 bisque?

1 hour ago, JLPicard said:

the pieces actually came out white and a good sound.

This means you got to at least 1000F, which is when chemically combined water is driven from the clay, making it permanent (won't slake down when wet).

I suggest finding some books that explain the basics of firing ceramics and kiln building, especially if you plan to make functional work (meant for food or drink). If you're just going for decorative effects, then pit firing and other primitive firing techniques are great. But for food you need to get to at least 1850F for low fire glaze.

[neilestrick]

Forgot to add: A pit firing will never get to temps that melt glaze or vitrify  clay, but a proper wood burning kiln can easily go to cone 12 or higher. So if you want to fire with wood and make functional work that's very doable. But you'll need a properly designed and constructed kiln to do so.

[JLPicard]

Thanks for the info so far. From the videos I've  watched it looked like only decorative or non food items would be achieved and that's fine for me. I can still use the studio to produce food grade glazed pieces, they just built a large gas fired kiln for cone 10 and are in the process of fine tuning it. I gave a few pieces for the test and await the result. one more question re: wheels what is the consensus on the wheels on Amazon for $159-200  the ones with and without legs. I can't afford  1K +for a commercial/professional wheel.  Sorry L&L no disrespect intended.  :  )

[Hulk]

Have yet to read/hear a positive review o' that class of wheel (<$200 new) from someone who has used one for a few months, let alone some years.

[PeterH]

Are you intending to bisque the pots in the studio first?

[JLPicard]

Peter, No. I know I don't always glaze my pieces, just what I make for drinking, eating (very few) and our pet bowls. Everything else I create is decorative whimsical / functional and either paint with acrylic or enamel. I don't get charged for bisque but sometimes I have to wait for the rest of the open studio students to finish their projects before the kiln is filled and that has taken up to 8 weeks, Too long for me to wait so learn to fire my own.

I added a photo to my gallery of my first mini wood kiln firing

 

[Bill Kielb]

15 minutes ago, JLPicard said:

I added a photo to my gallery of my first mini wood kiln firing

 

Hmm, given all that effort you may want to build a functional propane fired kiln. Lots of plans for repurposed old scrap kilns and ………they usually can fire to cone 10 if one desires. Definitely bisque and fire to cone 6 relatively easily. A nice learning experience for most, I think.

[oldlady]

about the wheel.  the low cost ones are garbage.   save up for one on craigslist or on the website where government sales are advertised.  they are scarce right now but maybe someone who thought last year that pottery would be  fun during the enforced seclusion of the covid scare has realized that they do not want to work that hard.    you do not have to buy a new anything, just wait a little and look a lot.   do not look at the old amaco egg shaped wheels with two speeds that the government listings show.  just laugh.

your last line mentions L&L.  they make kilns.   are you really looking for a wheel or a kiln or both?   and do not forget that cone 06 is not cone 6.

[JLPicard]

in my younger day I learned on a kick wheel, I've yet to find one on the lists not needing a concrete wheel or welds repaired and they're quite large and not easy to move around. Oh and I was just acknowledging  their post. If I can insulate correctly and get a few more firebrick for the fire box and a terracotta chimney insert, I'll re construct soon or have to wait till spring. I'm gen x and just looking to re-engage in something I liked as a teen and be as frugal as I can safely, and economically funded, so I'm trying a sawdust/pellet combo above ground "pit" kiln. Saw several clips on them, wrapping pieces in different materials producing interesting results.

Have to make a number of chachkies to test. will report in a couple of weeks. Did I ask if pre heating would reduce the chance of exploding in either of the 2 kilns?                                                      Thanks all, I use advice to learn. I do have to find a better way to get android photos on a macbook

[Bill Kielb]

23 minutes ago, JLPicard said:

If I can insulate correctly and get a few more firebrick for the fire box and a terracotta chimney insert,

Hmm sounds like fun. Insulation is key, though terracotta does insulate a bit but melts at or less than  1000c / 1800 f. Its great for natural gas flues etc  where temps don’t exceed 600-700 f. I wouldn’t make it my go to solution for the flue.

Not to be ignored, lots of folks have made very economical fiber kilns as well.

[Russ]

If you want a hotter temp do upgrade the brick and chimney and introduce air thru some sore of blower. Its the addition of oxygen not fuel that will do this. You might come up with some nice vitrified pieces with mature glazes. Oh and save up your money for a better wheel than the table top kiddie model. You''ll thank yourself later. Nothing but headaches and folly follow that .

[JLPicard]

Thanks Russ, I do have a small sized 3 speed metal fan that I use to get more oxygen into the kiln. And NO tabletop here but I am contemplating one of the more inexpensive floor models I see on Amazon. Reviews are consistent re: the product. Compact is what I need.  I'm not expecting 20 years of use, I'll be in my 80's!

[Mark C.]

Those amazon wheels may last a month or two-better to burn a few hundred dollar bills for the thrill than be frustrated with a new broken wheel. We hear alot about them breaking or busted out of the box. You get what you pay for with wheels.

[JLPicard]

Bill, I'd be shocked if I got it over 900f! It is small 2-4 pieces. My dig. thermometer goes to 750f and I get " high temp warning" at feed end and out the chimney. Have done 4 firings only the first had breakege last 3 none

[Bill Kielb]

2 hours ago, JLPicard said:

I'd be shocked if I got it over 900f! It is small 2-4 pieces

Isn’t your intention to get these at least over 1000f though?  Once all chemically combined water is removed, the object becomes more stable as in water will not make it go back to being clay.

Either way, sounds like you are enjoying the build and firing  experience with clay, kilns and learning  some combustion theory.

Here is an environmental idea  if it strikes you: since trees are mostly carbon and wood comes from trees, maybe plant a few trees to offset the carbon - good for the planet anyway.

[JLPicard]

Bill, I'd have to build a much larger kiln to reach that, If I want glazed pieces I go to the studio and have it fired there.