Pottery

>>1096709
Processing the clay before the forming is quite important. Do you want to create a large container to cook in? Put more organic particles in your clay dough, so when the container is being fired the organic part will burn and you'll have a comparatively easy to pick up pot. Do you want a fine cup to drink from? Be sure to spend more time on filtering all the small particles from the clay before you start processing it.
It's my third year studying Archaeology and I'm specializing in Prehistory. The stuff the Australian man from your picture does is quite authentic, it's my favourite Youtube channel.

>>1096709
Depends on where you find it. It comes down to how workable (plastic) it is, and how much other shit is in it. I'll give you two extremes.

Riverbank clay is nice and smooth. It often only needs to be dried out a little bit to use straight up. However, it usually has so much organic matter in it (rotting plant shit), that the loss on ignition is very high. This means that it'll shrink a lot more than purer clay, which means it is very susceptible to cracking during drying and firing. There may also be big rocks and shit in there that fuck you up when forming things.

Now let's say you dug a couple feet down past the soil layer somewhere to find clay. It'll be relatively purer (and doesn't stink), so you won't have a crazy high shrinkage rate, but it's chunky and too dry. It needs to be broken up into small pieces or powder, then needs a lot of water added to make it the right consistency. There may be rocks and shit in there that need to be picked or sifted out.

A good field test for whether or not a clay you find is worth a damn is you prepare a tennis ball sized amount by either drying it out or crushing/wetting it to a dough consistency, rolling it into a pencil-thickness coil, and wrapping it around your finger a few times. If it can do that without cracking into pieces, but stays in that shape when you pull your finger out, it's good clay.

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>>1096725
>>1096726
Thanks for your responses, I guess that's all I really wanted to know.

Try looking up the processing methods for companies that still offer "raw" or "natural" clays and see if you can simulate it on a small scale. Industrial clays are heavily processed from raw materials and lightly fired at one point, so often they need some time to mature to a nice throwing consistency. I think in the US, Blackjack is the only commercially available natural clay. You might want to look into the Archie Bray foundation, as they've done extensive research into domestic clays and regional sustainability in the ceramics field, so the may be able to point you in the right direction.

>>1096766
Thank you, I'm not really interested in using it commercially or semi-commercially, just out in the bush as a hobby.

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>>1096725
This is why I come here. 1 time a week some autist like myself can't fully be served by Google. Just too much info and clickbaitI. Then anon shows up, I am a PhD in clay pottery. Do this! Fucking love u faggots. Not trolling at all. U fuckers make me happy

>>1096773
honestly can't tell if this is a critique of my post

>>1096766
Wait, what? Are you talking about prepared moist clays? Or is a bag of OM4 that was levigated and had the rocks and shit screened out "highly processed"? Besides that there are a buttload of commercially prepared moist clays without any grog content, what the heck does that have to do with plasticity and maturing clay? The reason commercially prepared moist clays are sometimes short is they throw sacks of raw into a mixer with a minimal amount of water so they can immediately pug it without having a huge space to dry out tons of slurry. Over a month or two the mechanical water slowly seeps in between the clay particles, making it more plastic. Ages in the bag! Now if that sucks for ya, you can always call 'em up and ask them to make it wetter (thus faster to age) if you don't mind ordering a half ton or larger batch. The fuck is unnatural clay? Raw? Domestic? What the crap? There are assloads of domestic clays available. The mining companies dig it out, pulverise it, remove the rocks and shit, and sometimes mix giant storerooms of it around with a tractor for lot consistency, then conveniently bag it up for you in 50 lbs sacks. You can totally buy this shit, measure it and blend it up to your specs.

>>1096814
I think it was a backhanded compliment, you nerd. I got a question for ya: Are you going to be a good archaeologist or an evil archaeologist? Prehistory suggests good, but I am leery.

DIY is a drug free board, take your pot thread elsewhere. Read the fucking sticky!

>>1096709
Extremely important. All physical properties of ceramics are affected by the constituents. So you what to process the clay down until you have, as close as possible, to pure clay. From there you can add in adulterants in the specific proportions necessary to attain the desired properties in the finished ceramic.

So, for example,pure clay will shrink remarkably when it dries and when it is fired. To avoid this you add non hydrated materials (sand, crushed up fired ceramic, etc). The more you add, the els the piece will shrink, but at the same time it will become less elastic and cohesive, and more difficult to work.

There are myriad adjuncts you can add but it is a rather involved science ad beyond the scope of a simple 4chan post. Also I don't really know it, having only taken basic ceramics, gen chem, mineralogy, and crystallography.

>>1097476
I was under the impression sand is one of the worst things you can add as a temper.

http://ceramicartsdaily.org/ceramic-supplies/pottery-clay/going-local-how-to-dig-and-process-your-own-clay/

>>1096912
> I got a question for ya: Are you going to be a good archaeologist or an evil archaeologist? Prehistory suggests good, but I am leery.
What do you even meme?

Wow, I came to comment on this give my years of clay body studies, but most of the core stuff is already covered well in this thread. Some people know their stuff I am impressed.

As to OP, it depends on your application and sourcing, but an hour or two of simple processing can yield significantly better results, so it is worth doing. Even basic brick manufacturers will source from two or three sources and mix to get the desired ratios. Note there are super cheap manufactures that don't bother, but I wouldn't buy their stuff.

It is funny how many traditional ceramic manufactures fight for the cheapest substitutes, while the advanced markets spare no expense to make it as close to perfect as they can.

I find a high ball porcelain with some fortifiers and simple particle size control to be a nice middle ground, but their high firing temps can be a pain for most basic setups and that few dollars more can be a deal breaker for some.

There are a lot of things that go into ceramic manufacturing. What are you dealing with? What are you trying to make, and how are you firing it?

Given I tend to take things a bit far I would likely "engineer" my clay. It is frighting how one can get decently pure ingredients from regular stores. Like how wood glue has the same core binding additives I used in the technical lab. Makes me wounder if I can just grab things off the shelf and make a very complex clay in my garage. One of these day I hope to test these mad ideas.

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>>1097834
Thanks for your response.

If I didn't bother to purify how different would the end product be (say for instance in an oven and a pot) assuming my source clay is from a bit deeper.

>>1097836
Are you making a oven or firing in an oven?

You didn't really describe you source material or your base line. So How could anyone compare it?

A bit deeper? Where are you getting this?
It is like when people say they add sand to the clay body.
I really try not to murder them. White sand and red sand are chemically different, and don't get me started with black sand. And old sand and new sand have very different particle sizes and geometries. All of those details change eveything.

>>1097863
Making an oven.

I have no idea about the source clay.

>>1097867
What is your thermal cycling look like?

I would assume a fair amount of course white sand as it will cut down on shrinkage, assuming it is white from high silica/alumina content and not some color additive, a larger issue for repetitive thermal cycles like an oven.

You might what to look at how they make refractory bricks (a.k.a. fire brick) as that is what they use to line industrial ovens and stuff.

Seems like a good opportunity to ask:

How do you burn clay to turn black?

There's a local open workshop ("makerspace" in english I think) where you can work with clay. They have white, red and black clay, but the black clay turns reddish brown in their furnace and they don't know how to turn it black (apparently they learned their stuff from some pottery guy, but he wanted to keep some trade secrets).
From some casual online research, I've read about higher temperature, and/or changing the oxygen/carbon. Anyone can help me with that?

>>1097889
Mason stain are commonly added to stain clays new colors, black usually uses some manganese dioxide. Although they is a special Mexican clay that is naturally black.

The stuff behind it is actually very complex as colors are more chemistry based then pigment.

Also when dealing with such matters always assume it is not food safe till proven otherwise, some reactions are dangerous so understanding how you are venting the furnace fumes is not a bad idea as well. Though in most cases they are safe enough to touch once fired, just don't lick them and such.

>>1097899
I'm fairly certain that it's not colored with Manganese oxide, that would have to be indicated (with some chemical warning sign) on the packaging where I live.

>>1097911
The unfired body may be black, but you said that's not the fired color. Post-firing shades of red and brown may contain manganese dioxide, but they probably don't, or not in a high enough proportion to be dangerous. It's usually just FeO (black iron oxide) instead of Fe2O3 (good old red iron oxide). Probably harmless.

>>1097899
On the other hand, a truly black-firing body, a black basalt ware type body is most definitely chock full of MnO2, and it is very toxic upon dry inhalation, and highly toxic manganese fumes come out when you fire it. You must absolutely fire these bodies in kilns with good ventilation, lest you suffer neurological damage or death from the poisoning. However, afaik, when fired to maturity they are food-safe. An easily obtainable example of a commercially available prepared moist clay body of this type is Cassius Basaltic (cone 4-5) made by Aardvark clay, I think. But. yes Mason stains (which are a brand of colored ceramic frits, for those of you who don't know) are a good way to color bodies and surfaces. Black is a very hard color to stain the entire body though. It takes a hella lot of pigment ($$$) to get deep hues, so most people apply colored slips or glazes to the surfaces for economy. Best practice is to approach all things ceramical with caution until you know what the fuck they are though.

>>1097889
Anyway, there are so many ways to get a black ceramic surface. If you tell me precisely what you want to make, what precise properties you want this black surface to have (shiny, matte, dry, etc.), and its function (sculpture, pottery) I will list off ways to do it.

>>1097889
>How do you burn clay to turn black?

https://en.wikipedia.org/wiki/Pottery_of_ancient_Greece#Firing

Basically, it's all about painting the surface with filtered clay, so clean it's liquid, and then firing it in several stages, with and without oxygen.

>>1097939
>If you tell me precisely what you want to make,[...] I will list off ways to do it.

I can't give you much information, I'm afraid. I just started experimenting a little with pottery and to be honest I haven't a clear image of what I want as I'm just experimenting and have no intention of getting into it very deep. I'm mostly curious because one of the workshop guys is a friend and I find it an interesting topic. So while I'm thankful you don't need to put too much effort into this.
Anyway;
The Clay in question is this:
http://www.boesner.at/plastisches-gestalten/holz-ton-speckstein-7/ton-fuer-profis#166721
(select the lowest from the drop down menu - Terra 501)
Which they burn at 1050°C (no other parameters are known to me, but I think they leave the vents open and the room ventilated)

>I'm doing some sculptures and I'd like to get them darker (whatever is possible with that clay)
I'm still waiting for the first batch (they're only firing once there's enough to get the oven full), so I can't give you any images yet.
shininess/matte doesn't really matter.
>I made a clay plate with an imprinted image from a leaf and I'd like to make the leaf more visible
It's also made from the dark clay linked above, and while I will probably just paint it in a lighter color, the shininess you mentioned above made me curious: Can I make a part of the image more shiny/matte?

>Independently of the above, I'm curious about parameters you can change with a given type of clay to change the color
Notwithstanding any glazing and coloring or otherwise chemically altering the clay before or after the firing, what can be changed to influence the final color? Temperature seems to be one thing, and the oxygen availability apparently. Any others?


>>1097939
>>1098259
Ah, that's interesting. Thank you for this. So basically you control the available oxygen with the vents to allow or restrict Redox reactions with the Fe/Mn oxides; and different oxides simply have different colors.

>>1098333
Yeah, but you're not going to be able to do >>1098259 easily in an electric kiln, which I'm assuming they're using, since the firing temp is 1050ºC (pyrometric cone 06). The atmospheric conditions in electric kilns is by default oxidizing. The standard electric coil resistance elements are Kanthal, which only last in high temperatures when an oxidative coating is present. To just throw combustibles in the kiln at high-temp to achieve a reduction atmosphere–while technically possible–would destroy the elements in just a few firings. Rough cost analysis: $110 per firing if the element survive 3 firings and electricity is about $10 per load. They won't do this. Although it's really neat what the ancient Greeks did with their black-figure pottery.

So yeah, since cycling atmospheric conditions in the kiln is out of your reach, your best approach is chemically colored surface applications. If you do want to try to score some of that MnO2 basalt clay, which is potentially dangerous to work with and difficult to fire successfully I can talk you through it.

In general sculpture-speak these surfaces are referred to as patinas. In ceramics, they are known as just surfaces, but are broken down into categories based on the relative proportions of the base material. From most glass-like to most clay-like:
Glaze
Vitreous Engobes
Slip

The base medium proportions can be altered to give you any surface quality from shiny, semi-glossy, matte, dry. Metal oxides can be added to give you any color. The judicious use of application, resists, spray guns, etc. can give you any combination of surface effects and colors you desire.

One very simple way to do this would be to apply a black commercial underglaze to the base sculpture, then apply a commercial glossy clear glaze over top of that in the areas you choose. Be sure to use a glaze that matures at 1050ºC.

>>1098452
Thank you very much, that was exactly the kind of answer I was looking for.

>If you do want to try to score some of that MnO2 basalt clay, [...] I can talk you through it.
Won't be necessary, thank you anyway.

I'll experiment some more on Thursday.

>>1098452
"Underglaze" is slip (liquified clay suspension) that is partially fritted/calcined (pre-fired, ground and sifted to reduce shrinkage) that can be easily applied to the clay at any stage. It is usually exactly the same color as it fires to because the colorants are also fritted metallic oxides. This is why it tends to be expensive compared to say buying a bag of Iron oxide from a ceramic supply company. Ha, I'd just buy a pint jar of Amoco brand Velvet Velour Black underglaze and be done with it. Gloss it up by spraying or painting glazes over it as needed.

>>1098455
No problem. I've been doing clay shit for 20 years.

>>1098452
What if you put the pottery in a sealed container with wood at the bottom?

>>1098523
That's called a saggar. Yes, It could work well at that low temperature, but it does not work well in stoneware temperatures (1200C+) because all the combustibles would be long gone and the ash may turn to glass. Historically, saggars were used for the opposite reason before electric kilns, to keep the fly ash off the wares, and to minimize the color-changing effects an incomplete combustion atmosphere has on the metal oxides in the clays and glazes. Think of this as the oxygen-hungry, rich fuel to air ratio stripping the oxygen molecules from the colorants. Oxidized copper (Cu CO3) is blue-green, where as metallic copper is reddish orange when it's stripped of its oxygen molecules. A lot of metals have similar color-changes like that when they're heated in different levels of atmospheric oxygen. Because they get "frozen" and sealed in the amorphous glass (or glaze matrix) until cooling, they stay that way for a very long time or permanently.

Anyway, a saggar loaded with combustibles, fired at cone 06 (1050C) only gives you one shot–one level of reduction–so the ancient greek thing is still ruled out. But it opens up a hell of a lot of other things to play with. Go look up saggar-fired pottery and western-style raku (not technically saggar-fired, but the ceramic is pulled from the kiln at peak temp, and put into a make-shift saggar filled with combustibles to give it a very strong post-firing reduction atmosphere. Personally, I'm a big fan of the carbon-blacks you can get from post-fire reduction of low-fire temperature ceramics. However, they may only be colorfast for 50 years. Time will tell.

Yeah, so just take the clay body and form open cylinders from thick slabs. Make flat slabs for the top and bottom to enclose the saggar box and pre-fire up to cone 6 before you use them. Otherwise they won't be very airtight. Then go to town.

>>1098539
People put all kinds of fun shit in saggars to get colors and patterns: metal oxides and carbonates, salts, steel wool, ferric chloride, every manner of plants, fucking toothpaste, eggshells. Expect it to still stink and for a good deal of smoke to leak from them which could possibly hurt the kiln. Refresh it by doing a clean firing every other load to reestablish the oxidation on the kanthal elements. you might get a tighter seal with a layer of fine silica sand on the joints when you set the boxes.

>>1098546
The fun part about kiln work is that when you heat or melt various things, all their component elements come out and migrate/intermingle. Traditionally burnished ceramics or things brushed with terra sigilata (micro-fine, colloidal slip suspension) look particularly rich in saggar-fumed firings. This is how all those shiny, jet black native south-west American pots are done. You can do it much more reliably with modern tech.

Knowledgeable clay guy, I gotta say, goddamn do you know your stuff. I'm a student potter so I've just been working my hardest on getting my throwing skills and sense of aesthetics up to snuff, but there's so much more to know that it gets my head spinning.

Is there a definitive resource/book/books you'd recommend for someone mainly dealing with Cone 6 stoneware? I'm going to be able to mix my own glazes from raw materials soon and I'm feeling a bit overwhelmed.

>>1098640
Ah, cool! Sounds like about the right time to start the sciency shit then. The capable craftsman develops both the artistic and technical sides. What's your studio situation like? Class format and all that?

If your head is spinning from the possibilities it probably means you're inquisitive. Feeling overwhelmed is totally normal.

Since this isn't an answer I should pull out of my ass, I pulled an armload of books off my shelves. I'll go through them and make some recommendations later.

>>1098640
>>1098738
My shortlist picks for you:

The Ceramic Spectrum –Robin Hopper
Imo, soon to be recognized as a modern classic in much the same way Daniels Rhodes' "Clay and Glazes for the Potter" is, but consider finding this one too.

Cone 5-6 Glazes 2nd Edition –Edited by Bill Jones
Wow. Newer book. Every chapter is an article written by a modern master who may not have published a comprehensive book on the subject. Very pertinent, good photos. Wish I had this one 20 years ago.

The Complete Guide to High-Fire Glazes –John Britt
If you should ever find yourself with access to a cone 10 reduction kiln in the future, you want this book.

>>1099163
Thanks muchly! Going to research these a bit and see what I can afford.


I'm very much in a collegiate classroom situation. Electric kilns for the most part, with larger gas kilns available for reduction, but the reduction can be a bit iffy at times, I've learned. There's also a soda kiln, but nobody uses that one apparently.

>>1099209
Aw, shit, man. A fucking playground. You need to learn to fire that gas kiln if the current fireman sucks, especially if they've got an oxygen sensor probe. (If they don't, I have a low-cost solution for you) Im'a slap the next oldfart I see who does a body reduction-neutral-glaze reduction schedule. No excuse for that kind of guesswork anymore. But seriously, take initiative and hang around all the time and pester the professors. Don't you want juicy copper reds and opalescent Chuns?

What texts have they assigned to you thus far?

>>1099222
Texts? Fireman? oh ho, I'm so sorry, I'm at a state college with a general Bauhaus style curriculum, it's all demonstrations and the occasional photocopy from an old book.
They fire the reduction kilns I think with just a temp probe stuck in, and judge the reduction by eye. The graduate students are in charge of most of the gas firing duties. Saw a ceramics 1 mass bisque go in and get accidental reductions and overfirings all over the place, pinks and oranges and yellows all pulled from our humble cone 6 shop body that comes out a decent white in oxidation.
I think if I want good results, I'm going to have to either concede to the electric gods, or double down and take control of a firing.
One of the profs did suggest I give the soda kiln a shot in the upcoming semester, because, to paraphrase his words, they've never had good results with it.
Right now I'm on break, using my little closet Aspire wheel to fuck around with form and texture.