Colorado’s Ceramics

[HorseloverFat]

I dig it, though I like stiff ones with a through to punch out slugs from the other side.

Finally found me one of those, what I thought were "blunt tubes", that turned out to actually be some kinda vape thing container, but it should work quite well, for my smaller round stuff.

I like the look of that shiny one you got.

Sorce

Hehe!!! Spatula handle..

Cause I’m a Sponge Fry-Cook!

Arby’s straws have a larger diameter than any other... I know this from ..um... eating stuff with my nose in a past life.

 

[HorseloverFat]

@Colorado I forgot to mention...... If you get pottery tools, try to invest on some decent ones. Not the Chinese junk you find on Ebay or Amazon. Kemper tools are really nice and have an edge on them. It makes working with clay so much easier.

My Augernis set works well..

But NOW... my assorted pottery “tools”.. fill up drawers.

 

[sorce]

Spatula handle

I wouldn't ever have expected that!
Nice!

Sorce

 

[HorseloverFat]

My Augernis set works well..

But NOW... my assorted pottery “tools”.. fill up drawers.

I think the Augernis set is a “cheapy”

 

[Colorado]

I may not be the best person to discuss slab built pots with. @mwar15 @sorce @ABCarve would be the potters that work with that method from what I have seen here. What I can say though is that proportions is the key to making a pot. Pots that are not in proportion may be fully functional, but may not be aesthetically pleasing to the eye. Also I suggest you join a pottery studio or at least take some hand building classes to get access to a kiln. The reason I say this is because most all pottery studios will not fire pottery that is not made with clay that is not purchased from their studio.

My critique.......you should provide top, side, and bottom views along with something that can give as a judgement on size. Looking at your pics I have no way to understand the size of the pot unless you provide measurements. Even with measurements I would have to pull out a tape measure or ruler to look at. Simply adding say a pencil in the picture I can immediately understand the size of the pot. I like the design. The length x width seems appropriate, I can't say about the height as there isn't a side view pic. You need to work on your seams. Ensure they are joined properly as seams can open during the firing process. If your clay has grog pay attention when smoothing out the pot especially when using a sponge.

Your drainage holes look excessively large for that size of pot. I would make them smaller and add wire holes near each corner. Since you mentioned these pots will be unglazed everything you leave on the pot will show. So unless you are wanting a specific look always keep that in mind, glaze can help "hide" imperfections. Dry slow to prevent warping and cracks.

What Cone does this clay mature at? Absorption rate? Shrinkage rate?


Poke a hole with a pin tool or long nail, then enlarge the hole with a drill bit to the desired size when the clay is leather hard.

Thanks for the honest critiques! Totally agree my joints need work. I’m thinking also maybe a smaller coil would help it look more clean and less lumpy. Probably mostly just need practice

It is cone 5-7. Shrinkage 13%. Absorption 2.5%. Apparently it is made here locally. Here is a link to the clay:

Flagstone Clay | Rocky Mountain Clay | Clay for Teachers

Our Flagstone is a blend of two high-iron content clays, ball clays and other materials to achieve plasticity and strength.

rockymountainclay.com

Thoughts on the clay? @NaoTK ?

 

[Pitoon]

Thanks for the honest critiques! Totally agree my joints need work. I’m thinking also maybe a smaller coil would help it look more clean and less lumpy. Probably mostly just need practice

It is cone 5-7. Shrinkage 13%. Absorption 2.5%. Apparently it is made here locally. Here is a link to the clay:

Flagstone Clay | Rocky Mountain Clay | Clay for Teachers

Our Flagstone is a blend of two high-iron content clays, ball clays and other materials to achieve plasticity and strength.

rockymountainclay.com

Thoughts on the clay? @NaoTK ?

The only way to get better is with honest real feedback and with practice. Looking forward to seeing your next pot.

 

[HorseloverFat]

Thanks for the honest critiques! Totally agree my joints need work. I’m thinking also maybe a smaller coil would help it look more clean and less lumpy. Probably mostly just need practice

It is cone 5-7. Shrinkage 13%. Absorption 2.5%. Apparently it is made here locally. Here is a link to the clay:

Flagstone Clay | Rocky Mountain Clay | Clay for Teachers

Our Flagstone is a blend of two high-iron content clays, ball clays and other materials to achieve plasticity and strength.

rockymountainclay.com

Thoughts on the clay? @NaoTK ?

I have some thoughts on the clay company.. I have tried. The BMX...

It honestly sits exact bottom in my “bagged clay” rankings.. for.. a couple different reasons... I tried throwing Pieces with it on 5 separate occasions .. and produced NOT A SINGLE piece that either A:I was happy with. Or B: Held up structurally through drying..

I reclaimed the 10lb-sample I purchased and gave it to a wheel thrower.

This is, however the ONLY RMC body I tried.

 

[sorce]

Thoughts on the clay?

I reckon it will work well. I've found that absorbtion numbers tend to be rather conservative, everything under 2% I've ever tested has been vitreous.

The only issue with high iron clays, bonsai pots specifically, more specifically rectangle ones, is providing enough oxygen and time during the firing to properly burn out all the organics, especially before 1650F.

A passage from Frank Hamer's book A Potter's Dictionary of Materials and Techniques....
Between the highlights.


When seeking a kiln to fire in, if you can not find a mostly oxidized gas firing, I would be sure to use an electric kiln with a bottom vent, and request your work gets loaded low, as the fumes and gases that cause reduction or lack of oxygen tend to rise.

It is impossible to correctly fire high iron clays in any other situation without warping, especially footed bonsai pots, especially rectangles.

Sorce

 

[Colorado]

Interesting points. I love the red color but sounds like it will make it more challenging. I also have a bag of this:

Chestnut

Description: Like the name describes, Chestnut fires a rich, warm, mustard brown color. We have used the cleanest firing red stoneware clay as the basis...

rockymountainclay.com

Haven’t tried it yet, but it appears to have less iron (I think).

I already went through the 25 pounds of Flagstone so will report back with the Chestnut

 

[Colorado]

#3


I was aiming for a more geometric, industrial feel with this one. Shohin size, 6”

 

[Colorado]

#4

I had some scraps of clay leftover from the rectangle so I decided to venture into the mame realm. I don’t have a wheel (yet). So I coil built this small rustic round with an attempt at mushikui (“worm eaten” carving).

 

[penumbra]

I have never had an issue with firing red clays in any electric kiln. (that is in total about 8 kilns, most vented but not all.) Most of the clay I fire is red, some is brown and a little is white.
Also I have seen a lot of posting on this site about I love this clay but hate that one. Having worked for 8 years in kiln repair and supplies, several more in pottery, I have had the opportunity to use about 25 different clays, likely more. This is only mid range to high fire. (I will not use low fire clay even if its free.) I liked them all. From pure white porcelain to near black stoneware, from buttery smooth to so gritty it will take skin off your hands on a wheel, I never had an issue with the clay but I have had issues with the application. I couldn't pick a favorite clay, but I could pick a best clay for my various applications.

 

[sorce]

I have never had an issue with firing red clays in any electric kiln. (that is in total about 8 kilns, most vented but not all.) Most of the clay I fire is red, some is brown and a little is white.
Also I have seen a lot of posting on this site about I love this clay but hate that one. Having worked for 8 years in kiln repair and supplies, several more in pottery, I have had the opportunity to use about 25 different clays, likely more. This is only mid range to high fire. (I will not use low fire clay even if its free.) I liked them all. From pure white porcelain to near black stoneware, from buttery smooth to so gritty it will take skin off your hands on a wheel, I never had an issue with the clay but I have had issues with the application. I couldn't pick a favorite clay, but I could pick a best clay for my various applications.

No doubt you are the only person on earth, at least that I've come across, to either have enough sense or luck or thickness or proper firing schedule or patience or a combination of all, to make this happen.

I completely agree with the poorness of personal character that leads to hating a clay. (No offense, I know not of who you speak anyway, maybe me, lol! I may have said I hate a clay, but not hate hate, they just necessitate too much change of my process which I can't waiver from.) This is definitely due to my pick it and stick it attitude that is also present in my choice of one soil. I like to solidify decisions rather than float about in an ocean of options. I feel it's the fastest way to get things done.

You can't change a clay but you can change what you're doing with it.

There is nothing better than beginning with as many clay bodies as possible. Swimming the ocean of options to narrow down what fits ones process the best.

Truth though, if following just a couple efficiencies, not shipping clay, and a proper absorption rate, it seems no matter where one is located, the list of feasible options is already narrowed down to about 3 or 4 clay bodies.

I've found that the slight differences in manufacturers clay bodies isn't large enough to consider shipping from afar.
All Black Clays are basically the same.
Aardvarks Obsidian in California.
Kentucky Muds Black Bear.
Standards 266 in Pennsylvania.
They are all the same, or what is different could be more cost effectively altered with additions of local seperate materials or clay bodies. Shipping across states is never the more cost effective move.

I still find a blend of any 2 clay bodies to be superior to anything else. I think it is because of the larger variation in particle sizes. Every blend of Cone 6 and Cone 10 clays I fire in my Cone 8 middle zone almost refuse to sag or warp in drying or firing.

Sorce

 

[NaoTK]

I regularly make pots 24-30" with zero warp. The only way this is possible is by using an open clay with high grog and minimum shrinkage. If you were to use a closed clay your pot would vitrify, warp and dunt at this scale. I don't think we are speaking the same language if all you are attempting to do is make small bonsai pots (less than 12"). You can get away with any clay, even porcelain, at that scale. But guys, lower absorption is not your friend if you are trying to minimize warp. As long as you are below say 4% and have an open texture you are fine. Yes I live in Oregon but I have dozens of pots on the East Coast and Canada. Ever handle a large Tokoname pot? Super open texture. If you are slab building you don't care about plasticity. Lower the ball clay (high shrinkage)

Bonus: With open textured clay they dry super fast and evenly.

Under 12"? Use whatever clay you want, minimize warp with an open clay of high grog and low shrinkage
Over 12"? Use an open clay with 10% or lower shrinkage.

Try kneading grog and sand or kyanite into your clay body and make a rectangle. Make shrinkage test bars, measure the absorption.

 

[sorce]

I regularly make pots 24-30" with zero warp. The only way this is possible is by using an open clay with high grog and minimum shrinkage

Are you mixing these yourself?

I still believe in the conspiracy theory that is, the more commercial clay almost fits the bill but doesn't, the more clay one will continue to buy to "hone their process", where it is in fact impossible.

Also....

Are you utilizing clays that are non vitreous and frost proof? Is that the key?

Sorce

 

[NaoTK]

Yes I blend my own clay. Commercial clays are not optimized for bonsai pots. They are optimized for people who throw on the wheel and take classes at community college. In Tokonome the clay is blended specifically for bonsai pots per their specifications.

Vitreous=closed which means the body has been fused into a glassy matrix, and shrank and warped a bunch in the process. The whole bonsai pot acts as a single crystal, so it is susceptible to dunting. Can you make a warp-free vitreous bonsai pot? Sure, but as you all know its difficult. Commercial sip cast bonsai pots are quite closed and warp free, but they are slip cast.

 

[penumbra]

No doubt you are the only person on earth, at least that I've come across,

I know several professional potters who use red clay in cone 6 electric kilns and a few that fire red clay in gas kilns. I know half a dozen pottery instructors that use a red clay in their teaching asenal. The last 30 bonsai pots I made used Standard 547, a very groggy red clay. Works very well for the raw edges I am after.

 

[sorce]

Commercial sip cast bonsai pots are quite closed and warp free, but they are slip cast

The last 30 bonsai pots I made used Standard 547, a very groggy red clay

Both of these things leave out information that I find able to believe, but without information to know why.

A slip cast pot, without understanding it's composition, is still subject to every other and different failures as a non slip cast pot.

And, I've found that 547 can be underfired, still frost proof and good for use, and not warp.

Not expecting answers answers, just would appreciate the extra information that may go into further understanding why.

Cheers.

I really have nothing else to do today so I'm digging.

Sorce

 

[NaoTK]

I am inspired now to start a thread on slip casting, will do that soon.

Slip casting is shit on by everyone, including me, but if you ignore the total lack of artistry it is the superior manufacturing technique. The biggest advantage is that the pot is completely homogenous with no remnant stress and with completely even wall thickness. Combine this with complex geometry not possible with slab building, proper clay formula, and factory firing control and you get zero warp.

If you've ever studied casting slips there's a lot of clues there to apply to hand building. You will be amazed when you experience how little water there is in a fluid slip. Slip casting is thus closer to dry powder pressing (for making perfect tile) than it is to slab building.

 

[penumbra]

And, I've found that 547 can be underfired, still frost proof and good for use, and not warp.

My comment about 547 is simply that it is a red clay that performs flawlessly for me. Bisque ^06, oxides applied and finished at ^6. My bisque is about 14 hours and my final is about 11 hours. Most of this work was using a slab roller but I have used it on the wheel as well.
Most professional potter I know use Standard 308 for their red clay. It is very nice for throwing.