The Official "Ask the Artisan" Community Topic


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Re: The Official "Ask the Artisan" Community Topic

Postby paul haigh » Feb 10th, '14, 09:42

You can take some wet/dry sandpaper to the inside of that. Start with 600 grit. Use a little water. It should smooth that out considerably without ruining the beautiful flashing in there (very nice, by the way).

just sand a bit at first, then rinse and dry- remember that the texture is different if the bowl is wet or dry. You should get a nice satin surface.

I personally start with 200-400 grit, depending on the surface. Sanding is a normal part of the process for many wood firers.
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Re: The Official "Ask the Artisan" Community Topic

Postby JBaymore » Feb 10th, '14, 10:48

Hi Biglou....... good to see you over here from the CAD forums.

You are discovering one of the "rules" (all rules can be broken by a Chajin) for chawan that many non-tea studying potters do not "get". Yeah.... rough interiors are not so good for chasen.

If a tea practitioner is using a GOOD chasen ($$$) not good at ALL.

A lot of the "gnarly" chawan you see in photos are certainly visually dramatic and very beautiful, but for actual matcha use and certainly for actual formal Chanoyu use........ not very useful.

At an invitational international chawan exhibition I was involved in a number of years ago I invited an Ursenke master to come to the exhibition. She said she really enjoyed the internesting chawan there.... lots of differnt approaches and ideas..... but said that most of them could not be used for Tea (capital intended). Roughness/harshness of a number of areas of the forms was one of the prime culprits.

While many of my chawan are rough looking on the exterior, great attention is paid to the surface and contours of the interiors. (Just one of the reasons that the failure rate for my pieces "making the cut" is so high.)

There is a reason that in Japan certain types of wares are tended to be favored for chawan and chaire (tea caddies), and others are favored for other ceremony objects. Shigaraki yaki is not usually known as a major choice for chawan....... but is for stuff like hanaire and mizusashi.

I save the really "nasty" clays for mizusashi (fresh water jars), hanaire (flower vases), and sometimes stuff like futaoki (lid rests). I save the really "crusty" firing locations for the same. Often Chawan are put into saggars or behind "shields" that keep them from getting too much rough ash accumulation. Sometimes Chawan are fired upside-down.

As Paul has said, the wet/dry paper is in constant use for woodfirers. Also diamond grinding wheels of various sorts.

Yes, there is "bowl contact" when whisking, for sure. You are not "bearing down" hard, but you need to make sure that ALL of the matcha is getting blended into the water. Nothing worse than some dry matcha hitting your mouth!

For ceremony use, the host does not want a bowl that he/she has to be very careful in using so as not to break tines (and potentially kill the guest). Part of the nature of the ceremony is that it be very natural and effortless looking (even though that is FAR from the case until you've practiced it for 60 years). So "concentrating" on avoiding a chawan's "issues" is not a helpful thing.

However, some might say that having to deal with a bowls "imperfections" focuses the attention... and forces the host to be fully "in the moment" as the tea is prepared. Zen. I'd think most "mortals" at Tea would save this challenge to late in their development :lol: .

For "home use" you are into the ATW department. (Anything That Works.)

best,

.................john
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Re: The Official "Ask the Artisan" Community Topic

Postby bonjiri » Feb 10th, '14, 15:22

John excellent post !

need to stop thru here more often !

cheers everyone ! the learning process ! FUN FUN !

have a wonderful day !

aloha
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Re: The Official "Ask the Artisan" Community Topic

Postby paul haigh » Feb 10th, '14, 16:14

I have taken to cheating a bit by using a good dose of smooth flashing slip inside the bowl. Burnishing only goes so far if you have a gritty/funky clay body.
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Re: The Official "Ask the Artisan" Community Topic

Postby wert » Feb 13th, '14, 13:16

I am not sure if it is an appropriate question for this topic as I am asking in the context of yixing clay. In my simple mind, clay is clay....so do pardon me...

While I was washing my pots (yixing but different clays), I noticed that some pots would consistently dry off faster than others. What can one say about the properties of the clays that dry off faster? More porous? more metal? or anything you can conclude?

I apologise in advance for not asking a more intelligent question.
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Re: The Official "Ask the Artisan" Community Topic

Postby JBaymore » Feb 13th, '14, 15:08

wert,

Good question....... interesting to contemplate.

One possible answer is that the one clay is more porous than the other, so the water that gets absorbed into the pores of the clay is able to travel to the surface and evaporate more readily.

That being said............

Anotehr possible answer is tha the clay is LESS porous... and less water was absorbed into the clay to start with.

That being said............

Another possibility is that the darker clay (when compared to a lighter clay) absorbs more heat energy from the surrounding environment (surface emmisivity qualities), thereby facilitating faster drying because the state change of evaporation takes a lot of heat energy for it to happen.

That being said............

Ther surface area (microscopic) of a rougher clay can provide a differnt kind of wick for evaporation than a less rough clay.

That being said............

Could be a combination of things.

And so on...... You will find the correct answer to EVERY question relating to ceramics is "It depends". :wink: There are so many variables, that lacking a specifc set of data and the opportunity to test things... it is hard to pin things down to an absolute from this kind of information.

Metal content (predominantly iron, but likey with traces of manganese, copper, and/or other ones) probablu is not related other than as how the presence affects the poriosity factor. Some oxides of metals are fluxes on silica... and "tighten" a clay body in the firing.

I will say from my LIMITED experience with real Yixings....... there is a great difference in the porosity of the various types of clays. That likely figures in there solidly.

best,

.......................john
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Re: The Official "Ask the Artisan" Community Topic

Postby wert » Feb 14th, '14, 04:31

I had left out a possibly important detail, I washed my pots with boiling water. That way, the pots tend to dry out faster due to the residue heat. So how well the clay retain heat could also be a factor on the rate of drying.

JBaymore,

I can see right away you are an expert on the subject because you managed to answer my question very thoroughly but I come away feeling I know nothing. :D

If I understand correctly, the rate of drying out lies mainly in the porosity of the clay.

The two possibilities are mutually exclusive, porous and less porous. So, it is two schools of thought there, in the context of yixing clays which one is more likely?

As to the firing, clay fired at a higher temperature would be less porous, right? compared to the same clay fired at a cooler part of the kiln? Or is that another "it depends" too?
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Re: The Official "Ask the Artisan" Community Topic

Postby JBaymore » Feb 15th, '14, 12:02

The field of ceramics is highly technical. The are SO many variables... it is hard to make absolute statements and be 100% accurate.

Yup... if the pot is thicker and is heated, it will have more heat energy stored in the walls...... to help derive evaporation.

As a BROAD generality........ the more porous the clay the more moisture it will absorb into those pores. But at the same time....... it is POSSIBLE that same porosity allows moisture to move pretty freely back OUT of the clay. But not always...... hence the "depends" issue.

Generally speaking........ if you take a given claybody and fire it hotter, it proceeds to develop more of what is known as "glassy phase" in it. A fired clay is a mixture of crystalline materials and melted glass material. (Sort of like fiberglass resin penetrating the fiberglass cloth into a strong whole, stronger than wither element by itself.) The more glassy stuff... the less porous the fired claybody.

However if you plotted firing cone end point (for this discussion, think firing temperature) and porosity of the body, you'd get a sort of a parabolic looking U shaped curve. The clay would go from unfired on the left to overfired on the right..... and the bottom of the U would represent the most that particular clay could ever vitrify (develop glassy phase) before causing it to outgas and bubble inside....... and create small pores once gain. So it goes from porous to less porous to more porous as temperature increases. The bottom of that U is usually the target firing range.

Modern science (relatively modern, anyway) has been able to model the effects of ceramic chemistry on melting glazes, and we have very sophisticated software programs to model the properties that glazes will form. (In fact I was the first person to develop and sell commercial glaze calculation software for the cheap home PC machines back in the early 80's.) But to date, no one has been able to tie down exactly what is happening in a clay body to a level that a model can predict what is going to happen. Very complex subject.

best,

...................john
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Re: The Official "Ask the Artisan" Community Topic

Postby debunix » Feb 15th, '14, 13:02

I enjoy learning a bit about local rocks and geology when I travel, and that leads to pleasant comparisons and speculations about my teawares when brewing and drinking. This discussion adds another layer of appreciation....so I can contemplate the flaky glassy surface of the Flower of Forgetfulness Petr-yaki

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and note that it must have cooled a little faster than this smooth obsidian

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because it has large distinct flaky crystals, but slower than this mostly air pumice

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I wonder what conditions allow crystals to grow in a quite distinct matrix

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or lead to such dramatic drips

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I rarely get tired of looking at granite, large scale

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or imagining it in smaller things

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All of it--fanciful

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and technical alike--

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Image

it all adds to the pleasure of my tea sessions.
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Re: The Official "Ask the Artisan" Community Topic

Postby Drax » Feb 15th, '14, 14:16

Wow, those are some stunning comparisons....!
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Re: The Official "Ask the Artisan" Community Topic

Postby JBaymore » Feb 15th, '14, 20:06

Ahhhhhh you "get it" , debunix.

The nature of the geology of the earth's surface is what drew me into clay in the first place. Potters are sort of re-creating the volcanic origins of Mother Earth on a micro scale.

Note... studying the chemistry and formation of various minerals is highly instructive in understanding ceramic chemistry and how clays and glazes behave.

best,

.....................john
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Re: The Official "Ask the Artisan" Community Topic

Postby 茶藝-TeaArt08 » Feb 17th, '14, 04:03

Debunix, Thank you...really stunning and well-prepared juxtapositions of texture and effect.

Blessings!
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Re: The Official "Ask the Artisan" Community Topic

Postby 茶藝-TeaArt08 » Feb 17th, '14, 04:14

To the Artisans,

I am in the process of setting up a ceramic space for my wife to start working again in our garage. She has a nice wheel and we are wanting to add a kiln since the nearest kiln to fire at is a bit far from our home; plus it requires fees. We have been shopping online and looking for a used kiln. I spoke with Petr Novak on skype and he gave us his opinion. I'm curious if anyone has any recommendations on purchasing a kiln. We are looking at the small kilns that run off of 120 and fire to cone 6 or at a medium sized kiln that fires up to cone 10. We are thinking that the benefit of the small kiln is that we will not have to wait long to acquire enough pieces to fire a larger kiln, it takes up little space in the garage, etc. However in the smaller kiln my wife could not fire porcelain and would be more limited on size. Also we would not have to run the wire for 240, though running the 240 for a medium-sized kiln is not a really problem. For now her intention is to really mostly focus on bowls and teaware, not large sculptural pieces, etc.

We appreciate any wisdom anyone here has to offer on the matter. I am trying to get the space together for her sooner than later; she's a much happier person when she's expressing herself creatively and can sometimes forget how much this need is vital for her. :D Thanks in advance!

Blessings!
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Re: The Official "Ask the Artisan" Community Topic

Postby JBaymore » Feb 17th, '14, 10:29

teaart08,

The main problem I see is that the 110-120VAC electric kilns are REALLY small. I have one that I use for testing and small lustre and overglaze pieces. It is the biggest unit that 120 VAC can actually power..... and it is very small.

Even for a student, it would be quite limiting to scale. While turnaround of work IS improtant for the important feedback it provides a newer ceramist, I think she will be hampered in her development by such a small unit.

One of the concepts that I talk about in my kiln design classes is that the kiln in a studio is in many ways THE most important piece of equipment, because it is the "governor on the engine" or the "restrictor plate on the pipeline". The nature and size of the kiln you have dictates many aspects of the studio operations. It dictates the types of wares you can produce (firing type and range), the maximum scale in each dimension, and the turnaround time / cash flow (if a business venture).

I think that she'd be happier with a 220-240 VAC model. That does not mean that it has to be huge......... but I think a small one of these would be far less limiting than a 110 VAC model.

best,

....................john
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Re: The Official "Ask the Artisan" Community Topic

Postby GreenwoodStudio » Feb 17th, '14, 12:51

TeaArts-

I would also suggest going for a medium size, 240 v kiln. I really like a company called L&L kilns. I have one (I'm sorry but I can't remember the model #, I think it's a version of heir E23t) it's a medium sized computerized kiln divided into 3 rings. The really cool thing about this kiln is that I can remove rings if I want to, so potentially I could fire just one ring if I had a small load of pots or just wanted to test something. It's a pretty cool option.
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