Do Yixings really age?

[puyuan]

hydrogen peroxide is good too but harder to procure.

Is it hard to get in SG? It can be purchased at supermarkets here in the states. And I have used it successfully to clean a moldy pot, it does work great

diluted forms in pharmacies only they became sensitive/more controlled items after making into the list of "explosive precursors"

Aren't the 3%-6% concentrations enough for a good cleaning? I left a gaiwan away for a few days with wet leaves and it developed some very nasty mold. I was hoping to give it a good scrub with 3% h. peroxide before cleaning it again with cool water, boiling water and then leaving it exposed to sunlight.

[William]

My humble opinion is that to really understand how clay in general ages, a tea enthusiasts should use a new teapot for a couple of weeks, without pouring anything ot the external walls; this way should be easy to be appreciated the change in colour and acquired glossiness of the clay. I am actually of the opinion that the same results are obtained both using tea or just boiling water for a couple of weeks.

What most tea enthusiasts calls patina is just dirtiness deliberately created (e.g. pouring tea on the external walls, or letting soaking the teapot in a solution of tea and water).

Regards.

Aren't the 3%-6% concentrations enough for a good cleaning? I left a gaiwan away for a few days with wet leaves and it developed some very nasty mold. I was hoping to give it a good scrub with 3% h. peroxide before cleaning it again with cool water, boiling water and then leaving it exposed to sunlight.

Try to leave it in a pure solution of bleach for 24/48 hours, it should works.

[ethan]

+1 for the advice of William for bleach

After pouring out the bleach, I suggest a lot of rinsing & letting water sit in the pot for a day also.

[Tead Off]

Dirtiness might be an un-elegant way of describing a very natural process. When you use a teapot, there is a certain amount of leakage that spill out of the top and onto the sides of the teapot. This is sort of haphazard, leaving stains unevenly on the surface. Nobody wants a spotty pot, so the method for cultivating external 'patina' is to pour tea evenly over the exterior whenever using that pot or keeping it aside in a dish, and pouring a teapot full over it from another pot. The key to doing this over time is after the pot dries, rinse it in hot water and take a tea towel and buff it, rub it, etc, to induce the natural shine of the buildup. This induces the beauty of the clay and adds a lovely dimension to the teapot. No one would call this 'dirtiness'. Shame on you.

[ethan]

I'm glad Teadoff added some levity to this thread. I laugh at myself as well as his "shame"-for-"dirtiness" joking because I thought I was contributing to writing on getting rid of mold.

Nonetheless: Of course, yixing ages. We can nurture age, fight age, or just go along w/ it. I use a pot that sports patina & stains.

I won't worry about rinsing the outside w/ tea; washing it, &/or brushing it although I admire others' well-kept pots. I like the charm of the pot showing that it is being used.

[William]

Dirtiness might be an un-elegant way of describing a very natural process. When you use a teapot, there is a certain amount of leakage that spill out of the top and onto the sides of the teapot. This is sort of haphazard, leaving stains unevenly on the surface. Nobody wants a spotty pot, so the method for cultivating external 'patina' is to pour tea evenly over the exterior whenever using that pot or keeping it aside in a dish, and pouring a teapot full over it from another pot. The key to doing this over time is after the pot dries, rinse it in hot water and take a tea towel and buff it, rub it, etc, to induce the natural shine of the buildup. This induces the beauty of the clay and adds a lovely dimension to the teapot. No one would call this 'dirtiness'. Shame on you.

Here in Vicenza we have 2 old trees, old more than 300+ years and taller than 20 meters. They are situated on the border of two different small lands, belonging to two different owners.
Both trees get the sunlights only on one face of the trunk for the entire year, devoliping on the face exposed to the sun a light gray colour, while the rest of the trunk shows a light brown colour.

While the first owner every 4/6 months, uses a vegetable dye that he sprays on the trunk in order to obtain an homogeneous gray colour (since the upper part of the face of the trunk exposed to the sun is a bit lighter than the lower part), the owner of the second tree leaves that the colour remains different on the two faces of the trunk and slightly uneven between the higher and lower part.

Would you really call the colour of the first tree as patina?

[Tead Off]

I don't think your example is a good one, in this case. But, if your story is true, it is amusing in itself.

[SlowOx]

Kyarazen,

I just read your piece on Patina Development of Yixing Pots. Incredibly amazing information. Wonderful beautiful work

I have a few questions. You mentioned that "Some of the minerals present in the water can also bind to the clay in micro quantities." How did you come to this conclusion?

The theory of contraction and expansion still seems a little unresolved. Your example of the water being sucked back into the pot isn't clear evidence that the pot expands or contracts IMO. Do you have a macro lens that can take pictures before and after of one of your yixing pots that can see into the clay? Or... how did you come to the conclusion that the expansion is at 1cm^3?

Lastly (for the moment) How would you objectively measure wetability?

[JBaymore]

........only because it's a less porous area than the interior of the pot, given the higher intensity of the firing on the outside. I'm not sure about that though.

While it is a technical POSSIBLITY (if the measuring device was sensitive enough) that there is a difference in what is known as the Apparent Porosity of the clay material from the interior of the wall section to the exposed exteriors, in reality there will be NO difference. The walls of the Yixing teapots are so thin and the rate of firing temperature increase is slow enough that the thermal lag to the interior would be negligible to non-existent.

Were there any significant differences in this figure, they would be caused by differences in the relationship of glassy phase and crystalline materials in the body.... with very negative impacts on the structural integrity of the pieces..... particularly in the realm of thermal shock resistance.

Not a real-world factor that woukld affect anything to do with tea brewing. If there is any of this happening...... it would merely be a "scientific curiosity" that one could find with absurdly sensitive tools.

best,

..............john

[kyarazen]

John,

something to pick your brains on. it is interesting particularly for Red Clay/hong ni that when fired, the outer surface develops this matte shiny skin, whereas on the inside of the pot, it is a different color, different texture. this is a very constant observation.

only for pots that are Nei-Wai-Tu-Hong, or internally and externally coated with fine red clay, where one would see inside and outside similarly glossy.

also, if you crack a ROC era or Qing pot, the clay inside the broken edge is dark purplish black, the outside and inside surfaces are red with the inner surface rough matte, and the outer surface shiny matte/glossy. in this case, i dont think the clay is totally "oxidation" fired throughout the thickness of the clay

your opinion?
kz

While it is a technical POSSIBLITY (if the measuring device was sensitive enough) that there is a difference in what is known as the Apparent Porosity of the clay material from the interior of the wall section to the exposed exteriors, in reality there will be NO difference. The walls of the Yixing teapots are so thin and the rate of firing temperature increase is slow enough that the thermal lag to the interior would be negligible to non-existent.

Were there any significant differences in this figure, they would be caused by differences in the relationship of glassy phase and crystalline materials in the body.... with very negative impacts on the structural integrity of the pieces..... particularly in the realm of thermal shock resistance.

Not a real-world factor that woukld affect anything to do with tea brewing. If there is any of this happening...... it would merely be a "scientific curiosity" that one could find with absurdly sensitive tools.

best,

..............john

[JBaymore]

karazen,

That differential in color is a very standard occurrence in work that has been subject to reducing conditions in the kiln's atmosphere when the clay body is still gas permeable to CO and H2 gases. Any body that contains iron oxide will tend to show it.

Red iron oxide in this case is reduced (reduced valiancy) from Fe2O3 to the black state FeO. Red iron oxide is an ampoteric in the development of silica glass ....... network modifier. BUT black iron oxide is a powerful flux on silica. This will affect the nature of the texture of the body, depending on the exact nature of the melt. (It can also cause defects...... if the body becomes overfired.)

The glassy matrix developing in the body then will be not only fluxed by this oxide in the melt, but also "stained" because both red iron oxide and black iron oxide are colorants. SO the entire clay body will tend to get "darker" as the percentage of black oxide increases.

Then as the body tightens and becomes less and less and then eventually almost completely gas impermeable to OXYGEN........ the kiln gets shut off.

The kilns used are not typically sealed completely (even if the potters try mainly in an attempt o control the cooling rate drop), and the cooling cycles are long. So the outside of the pieces are exposed to the oxygen leaking into the kiln. In this area of the forms, the black iron oxide at the surface gets re-oxidized fully or partially to the red state. Hence the redder colorations od the surface. While in the interior, oxygen cannot have the same effect. So the insides remain "darker".

There IS a technique in which the kiln, instead of allowed to cool with whatever oxygen leaks in... is deliberately fed excess fuel during the decreasing temperature part of the up-then-down cycle. In this case the reducing conditions are maintained until the temperature is below the point at which the iron is still reactive to combining with oxygen. SO in this case the exterior of the piece still has some or all of the iron in the black phase. So the exterior of the piece will be dark also.

Variations in color can be controlled by the extent and duration of reduction versus oxidation and the part of the cycle in which they occur.

best,

...............john