Chinese brush pot

[Stan]

Hi Peter, I put this on your site before, I am putting it on again because I discovered something interesting, I put this next to a lamp and at knight when I was turning off all the lights, I found that the glaze glows in the dark, I know that it is fairly new, but I thought you would get a kick out of that, have you ever seen a glaze that glows in the dark?

[peterp]

Ah yes. I remember that I mentioned that the attire of the people depicted is Korean...

You know what phosphorescence and fluorescence are, don't you? 
Just in case not:  en.wikipedia.org/wiki/Phosphorescence
No, I never have seen these effects in glazes. Old glazes usually contain some minerals, but never heard that luminescence is involved with glazes. But I have seen minerals displaying these.
Maybe I should read the research documents from China, but don't have much time to do so.
Does it glow a long time? Did you find an explanation for that on the web?

[Stan]

Hi Peter, you were right on about the origin, I did a little research and found out, first of all the difference between phosphorescence and fluorescence, the glaze on this brush pot would be a phosphorescent mineral called Borate and it was used in modern glazes that go back about two centuries, but then excavations at an eleventh century site near the Great Wall of China found shards that contained Borates, I know, even the shards are faked to day, but these shards had been tested by Thermoluminescent test, the test showed the Longquanwu shards are from tiles that were made some 1000 years ago, It was then that the Mongols made near by Beijing their Capital, why they stopped using borates is unknown, my guess is that it glowed in the dark and they might have thought that is was haunted or something to that nature, that is just my thought, as to why they stopped using it in there glazes, it is unclear, but we now know for certain that the brush pot appears to be Korean like you said, if you want to read the whole article, you can google, Glow in the dark: Borate glazes proven a thousand years old.

[peterp]

Thanks Stan, I had wanted to ask you to tell me if you find out more about it. Learning never ends with Chinese porcelain...
The most common reason for changes in materials like clay or glaze is that the original ones were depleted, or they were sourced from another, more readily available place.

[Stan]

I also read that the boarates are very expensive and that is the main reason for not using them in todays porcelain glazes.