3 Things That Break Pottery in Firings and What To Do About Them
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- Опубліковано 29 сер 2024
- Many, many people think that green ware pottery cannot be fired outdoors without a high risk of breaking. I am here to set the record straight, green ware can safely be fired outdoors. In this video I outline the three things that cause pottery to break in firings and how to avoid them. Potters of the world unite, let's fire out pottery outdoors without breaking.
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Before I got linked up with Andy Ward my success rate with outdoor firings was frustratingly close to 0%. Now I'm 75% or better. Thank you Andy! Also, since I fire in my backyard I first thoroughly dry pots in the oven at 200f and then crank the oven up to the max for an hour just before they go in the fire. I think it helps to reduce the shock.
I was just discussing with Eric and Helene how you seemed to have firing down pat now. Thanks!
Had I been told by an individual that outdoor wood firing of clay is not achievable, I would have simply said there are thousands of pottery as proof that it is possible, go visit a museum to see them or go to a pueblo and watch them during a firing. As I enjoy camping in the outdoors, and many of us have spent many hours sitting around a campfire late into the night, firing a pot or two simply adds to the adventure. Thanks for sharing.
When I looked for primitive firing info, I used to grt so fed up with people claiming they do that but then it turns out they bisque first. Then I found you Andy.
Thanks! 🙏
Yeah, not sure what the point is of doing outdoor firing if you're just going to bisque it first!
Experimenting is the key. it took me a while to get to know my clay, and how to use the wood fire, but, the last firing was a 100% success.
The local pottery supply store told my daughter that a wood fire would not work to fire pottery. she bought some some of their medium fire clay, following Andy's video and adding temper i proved him wrong. the pots came out of the campfire real nice, without any cracks and are ceramic. They were even painted with red mineral paint which also worked.
Andy, another great video.
Great fun.
thank you for sharing with us
OU
Thanks Old Ugly! Proving the guy at the local pottery store wrong since 1989!!
2/10/23-9:50 AM EST
I’m getting such helpful info from your videos. I wish I had all this instruction 20+ years ago. Hopefully I will put it to good use this summer.
Me too, if this info had been online when I was learning it would have shaved years off of my learning curve. That is one of the things that motivates me to make more videos.
At least I might not be able to carry my pottery in my pocket anymore
I'm a complete novice. I've never used a kiln. I fired a few things I made from wild clay and sand following Andy's advice. I did get a couple of cracks but 75% came through perfectly. In my eye the cracks were at places of inconsistent thickness due to my lack of experience/skill. I'm very pleased, thanks Andy!
That's great to hear, keep going, you're next batch is bound to be even better
@@AncientPottery thanks Andy. Thinking about it, 11 out of 13 pieces unscathed is more like an 85% success rate. If I can achieve that on my first firing (and first pottery), anyone can do it. You're a great teacher, thanks again!
Hi Andy, Im from Argentina. I saw 3 of your videos and im already a fan.
Glad you are enjoying them.
Just fired my first pot last night and it cracked all over. No worries though. A few more and I might get the hang of this! Thanks for all the videos!
You're welcome
When I was first learning to make pottery, I had an instructor who insisted we use a scraper with teeth on it to essentially comb the clay. We were then supposed to then obliterate the scratches in the wet clay. I lost every single pot doing this from trapped air. Once I skipped that process I stopped losing pots.
I also take my fully dried finished greenware outside on a plastic table and let the sun heat them up for several hours. When pre heating I put them around the fire on top of flagstone pieces and never directly on the ground. OR I pre heat in my oven. Then let them sit a while on top of flagstone “kiln furniture” placed in the hot coals with no flames before stacking the wood.
I’ve never used an actual kiln. I don’t think I would even know how to beyond plugging it in.
One more for consideration, perhaps #1.5 that I run into quite frequently in the carbon-ceramics world, is thermal expansion and/or differentiation between materials. One of the things I most adore about graphite and a select few ceramic materials is that their preference when extreme heat involved is to rigidize in place rather than swell or shrink comparatively (the .001mm+/- normally doesn't concern me versus, say, the whole digits of steels) . Most heat-resistant metals (used loosely to involve high temp alloys like stainless and inconels, etc) on the other hand go through a funny cycle when heated, which first is to expand, then shrink when coalescing grain structure affected by cooling rate. Others will swell and ablate when pushed hard enough, while others still will turn into a fountain of sparks and shrapnel, daring you to push it harder until it unceremoniously throws in the towel and blows up in your face (preferably at arms length behind a blast shield, but sh!t happens!)
Reason I mention this is the microsom of the mineral world, even at the best of times, will contain traces of mystery meat if you will. Most of the time there's not enough to do undo harm, but as is the way of chance, chaos and the semblance of balance in between, sometimes you just have a freak concentration at micrometer scale that later introduces itself as a defect like an imperceptible pinhole which leads to a crack, and with enough temperature swings, an almighty fissure. The somewhat end event is thermal shock as a blanket term, but is most notably the most observable in the sequence of things.
To those who cant imagine low-tech firing without electric bisqing, i would point to the obvious, that pottery was done for many thousands of years before electrickery was invented.
Your pot that sat on the ground and aquired a damp bottom was (i think) sitting on soil that was warming up and i imagine that moisture was released by the warming of the soil deep underneath it. As the heat from the fire spreads downwards through the soil, soil moisture is driven out in the form of steam, which heads upward through the soils porosity as it is formed, partly because it is lighter than air, but mostly because it is 800 times bigger than the moisture in the soil from which it was created. If putting a spacer between the soil near the fire and pots being prewarmed prevents this cracking, then my theory works.
Thank you, I believe you are correct. I often set my pots on stones or sherds while pre-heating. But often out soil is very dry here in southern Arizona so I can get a bit lax about that.
2nd experience firing pottery just finished. 1st time it didn’t break but it didn’t fully fire. This time I air dried for 2 days and all 4 of my pieces exploded
Pre-heating is critical
very helpful, Thanks again Andy, we plan on employing all of these rules next time we fire, should be in the next month or so. I'm sure we will be successful this time do to our own prior mistakes and with the knowledge that we have gathered from this video and others you have put out. great video!
Glad you found it helpful. Can't wait to hear how your firing comes out.
1:20 this man and the amount of breakdown he had.
Been watching your videos over the past few days. I've always been fascinated with pottery, but it's always been too messy and expensive (when I was a kid) and I didn't know how to go about making pottery at home. I'm glad to have found your channel.
Welcome!
I'm curious as to what too much temper does. Will the pot just be difficult to build because it'll ruin the clay's plasticity, or will something happen when it's fired, or is it something else?
The downside of too much temper is just crumbly, un-plastic clay that is hard to work with. It can also result in weak, easily broken ceramics. Thanks for asking, it is easy to miss these kinds of details when making a video.
Good, simple, straight forward explanations. Well done.
Glad you liked it.
Thanks Andy
You bet
Thank you for this! I'm in the cold wet Pacific Northwest and I have to fire only on the hottest, driest summer days and preheat my pots in my oven to make sure they are completely dry and haven't wicked up any moisture just sitting on a shelf in the house. I don't seem to have any problems with overfilling, but this is a glacial clay, sort of blue-grey in color and almost acts like a stoneware. It has a lot of natural sand temper, too. I'm envious of your Arizona weather and variety of clays when it comes to primitive pottery!!
Sounds like you have found ways to make it work in spite of the wet weather. I have heard that our dry climate is perfect for pottery. I kind of feel like it is a liability because my clay dries so fast wheel I am working with it. Everything is a give and take.
Always good THANKS Andy,, just got my new slip clay from you ,look s fine can't wait to give IT a try.
Thanks Rob. I discuss how to use that slip in more detail in my upcoming video that comes out on Sunday.
@@AncientPottery Thanks I will be watching for it I did.see your bit about no levitating just wet and straining through a paint strainer. Thanks
It is more fun to kiln working outside. Button kiln is expensive but good for assembly line work.
Ive never heard of a "button kiln", will need to look that up.
I will be doing something soon I would like to do an enter view with them. Other wise sharing the things I did with the Hobby Lobby Clay. Thanks to this channel I do test plates and bowls now. I have used a lot of river sand worked best. This clay is very brittle. I thought I was doing something wrong. And after 2yrs I wanted to know more about this clay. It took me 24hrs to get some one but I did. I have used grit sand and chips from flint chips I ground up. It has the ability to make some clay vessels in a fire pit.
Once again thank you for sharing with the public what you are doing. You channel I wanted to know more about my clay. And I now have experimented in many ways. Now I am experimenting with many types of clay and doing many thing to it to see what comes of it. We're I am the clay is some what different but is all has the same Principles. Keep up the good work. You are on the target.
Every pot is a experiment. It is best to see what comes of it.
I certainly don't recommend that Hobby Lobby clay, but it is an easy to acquire option for many people. My recommendation is to get out and find your own clay in nature, this will connect your pottery to the earth and to you in a special way. Thanks for watching and commenting.
Just my thoughts … that pot that cracked from getting too hot could be from a blend of clays that had different fired shrinkage rates along with maybe low amounts of alumina and silica . Causing cracks at just above sinter temperatures
Interesting thought. That is my pot and it was a mixture of two clays. I've never had the surface burst like that in the past and I think it was too hot but your idea may have contributed to the problem. Thanks.
Always the chemist Jeff. I don't know anything about that kind of thing, but I do know that these sorts of results take place even when there is no mixing of clays.
@@airstreamwanderings3683 hey I enjoy your videos also ! Love your video touring the silver city museum. I am a mimbres fan. Just one more thought, and I ain’t no expert , but maybe wedge your clays a whole lot when combining from different areas that can help.
@@AncientPottery I agree! If your a potter your going to always have scratch your head moments !
@@airstreamwanderings3683 ok after thinking about it some more. I also throw pottery on the wheel and sometimes if the clay is not compacted to some degree often even wheel thrown pottery will get cracks like that on the bottom from not being pressed in or compacted in relation to the rest of the pot . Ok now I will stop 🙂
Thank you, Andy!
Welcome!
The Hoddy Lobby Amaco Clay they Cary X- 15 has oil in it so it can be remoist.
Hmm, skeptical but I will try it.
The other thing it is brittle. It brakes easy.
Thank You For letting Me share with you.
Very informative thank you . n yes everything was ether thermal shock or Spaulding I now know better .... And as you said " keep your temper" lol thanks again .
Thanks for watching. I am glad you are getting something useful from these videos.
@@AncientPottery well sure thing . I been fallowing you about a year and so far your one of the best instructors IV had. I try to adapt styles with your ancient techniques and create new things .
Great video! Thanks for your videos, they are very informative.
Thanks 24, where are you located? It looks like southern AZ and I think I saw some clay in your root cellar hole.
@@AncientPottery South Texas. Yes lots of clay here. I might do a video on my channel making pottery on the land. I’ll be sure to give you credit. Your info is very helpful
Nice video......for me preheating cracked some pots....fire got too hot too quick....
I don't recall every cracking a pot in the preheating stage. But at the kiln conference Cherylene was being very careful not to get the pots too close to the fire for fear they would crack.
Hey Andy, awesome video!! Thanks for the tips.
On a side note, I was curious if you’ve ever explored around the Gordon Hirabayashi area on Mt. Lemmon? I’ve found dozens of old pottery sherds while hiking in that area, all along the creeks and streams leading to Sycamore Reservoir. Some of them have really interesting colors. Thanks again
Thanks.
I am not familiar with the Gordon Hirabayashi area at all. I worked for the Coronado National Forest for years and in my experience there isn't much archaeology in the high country. So if you are finding sherds up in the Mt Lemmon area then that is extraordinary.
Thank you very much, but i think you forgot one of the main things that i have personally experienced. It is the symmetry of the fire around the piece. As you know in the outdoor firing the wind blows well and it can make some parts of the pieace more hot than the other parts so cracks appears, also the unsymmetrical installation of the wood around the piece makes some gaps and this also make cracks.
.
Can you please talk about how to avoid the black smock from sticking to the piece.?
thanks in advance.
Your problems with symmetry are really just problems with thermal shock and the answer is still the same. Add more temper. Add enough temper and you won't be so concerned about symmetry.
@@AncientPottery Maybe there are in the same category, but they have different reasons. You defined thermal shock as a rapid change temperature. I am simply talking about the case of having a slow rate of temperature with a good preheating. BUT some spots on the piece is more hot than the other spots. So it is called thermal difference as a subtitle in the thermal shock, I think. Maybe it is the same meaning but you didn't explain this reason despite you have cracked a good piece in your video and you said maybe because of the wind made a spot cooler than another spot. I just wanted you to explain this reason in your video to help those who face what I faced.Thank you for your helps your time.
Hi Andy. Are these pots food safe, or just decorative?
Well that's not an easy question to answer. Yes they can be used with food, all of our ancestors ate on pottery like this for thousands of years and here we are, but it is porous so you need to keep in mind that limitation. There are ways to seal it, both natural and chemical and it can be sterilized by heating.
hello. it's apart of the expierence . So, dig your own clay build your kiln make you pottery how you like,
yes temper, i saw two women from Papua Nuegiea anvil and pounder coiled pottery , then while the clay was wet, they stacked and started a fire around the pots. slowing building the fire. i expected the pots to explode, so i asked, apparently they used ilmanite black volcanic sand , they ever bought some with them to my city , firstly i knew nothing about this pottery nor the ladies who 's tradition was potters,
Can you mix sand, diatomaceous earth (mostly to use what I have, lol). Would do any harm? Thanks
Can any impurities in temper added to the clay cause it to break?
Is it possible to add too much temper and if so, what happens? I was testing a new clay I found, and the one I added temper to exploded while the nontempered one didn't 🤔
20 - 30%, is that by weight or volume?
Whatever way you want to do it will be fine.
I used limestone in my clay and the pot broke. Why is this
Limestone turns into quick lime at high temperatures which will cause spalls. Avoid limestone and all forms of calcium carbonate like the plague.
What happens if you put too much temper in your clay body?
It becomes weak
If you have an electric kiln why would you use an out door fire?
I could ask the same question the other way around. Why would you use an electric kiln when you can fire pottery outdoors?
Pre heat! Pre heat! Pre heat!!!
And temper, temper, temper.
Merci !
Thank you so much!
Fail. FIRST ATTEMPT IN LEARNING.