Ruyao: What's in a glaze?

[mudandleaves]

What's the difference between factory "ruyao" and the real thing? Find out in our latest blog entry, where we discuss the roles of vitrification, reduction firing, and the two key ingredients in the ruyao glaze recipe.
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https://www.mudandleaves.com/teatime-bl ... in-a-glaze
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4DA78AA5-B715-449A-BF91-3646FB5706B7.JPG (101.28 KiB) Viewed 5705 times

[pedant]

interesting.

so you're saying higher oxidation state iron oxide reduced to iron(II) oxide (or even elemental iron particles?) gives a blue-green color?
blue-green is not a color i associate with iron of any oxidation state, so i wonder if it's actually particles doing Rayleigh scattering or something.

i wonder if the 'royal jade' glaze from shan kiln has a bit more iron for a deeper color?

[Dresden]

interesting.

so you're saying higher oxidation state iron oxide reduced to iron(II) oxide (or even elemental iron particles?) gives a blue color?
blue is not a color i associate with iron of any oxidation state, so i wonder if it's actually particles doing Rayleigh scattering or something.

i wonder if the 'royal jade' glaze from shan kiln has a bit more iron for a deeper color?

The key is the reduced oxygen. In an oxidizing flame iron will present as yellow or brownish red. In a reducing flame iron will present as green.

[pedant]

The key is the reduced oxygen. In an oxidizing flame iron will present as yellow or brownish red. In a reducing flame iron will present as green.

more details about green iron, please?

[mudandleaves]

interesting.

so you're saying higher oxidation state iron oxide reduced to iron(II) oxide (or even elemental iron particles?) gives a blue color?
blue is not a color i associate with iron of any oxidation state, so i wonder if it's actually particles doing Rayleigh scattering or something.

i wonder if the 'royal jade' glaze from shan kiln has a bit more iron for a deeper color?

The key is the reduced oxygen. In an oxidizing flame iron will present as yellow or brownish red. In a reducing flame iron will present as green.

Yes, it's because of the reduction firing process:

"Finally, a reduced oxygen environment is an important part of the firing process. The sky blue or tianqing 天青 ruyao glaze recipe has less than 3% iron oxide. During reduction firing, the small percentage of iron oxide gives ruyao its light sky blue."

The exact recipes are closely guarded by Ruyao potters to prevent other studios from trying to reproduce their work. It means that among these studios producing ruyao each one produces something different from the others.

[Dresden]

more details about green iron, please?

Green rust is a form of iron oxide that occurs in low oxygen environments. It is commonly seen on the iron in underwater structures (that is the one I am familiar with). There are actually different types of green rust depending on the other elements present such as chlorides, sulfates, etc.

That is about the extent of my knowledge, but searching "Green Rust" should give you much more info on the subject.

[Bok]

Happy coincidence, the palace Museum has just announced it will display its Ruyao collection: http://www.taipeitimes.com/News/taiwan/ ... 2003717186
When seeing the pictures of contemporary Ruyao I always wondered why they call it sky blue, when it is more of a dirty turquoise – but seeing these original old pieces it makes sense, so much more vibrant and actually a sky colour.

Or are there different know shades of this glaze?

[mudandleaves]

Happy coincidence, the palace Museum has just announced it will display its Ruyao collection: http://www.taipeitimes.com/News/taiwan/ ... 2003717186
When seeing the pictures of contemporary Ruyao I always wondered why they call it sky blue, when it is more of a dirty turquoise – but seeing these original old pieces it makes sense, so much more vibrant and actually a sky colour.

Or are there different know shades of this glaze?

By "dirty turquoise" are you referring to the photo in the top half of the frame above? Those are mass-produced "ruyao" used to compare with fanggu ruyao. The colour is very far from sky blue 天青.

[Bok]

to me both do not look very sky blue. Compared to this: https://jingdaily.com/crowd-pleasing-so ... hong-kong/

[mudandleaves]

I think this might be useful to you. It's the industry standard for colours:

IMG_1871.JPG (170.62 KiB) Viewed 5540 times

[Bok]

I think this might be useful to you. It's the industry standard for colours:

IMG_1871.JPG

That is indeed interesting, thanks for sharing!