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Re...depth colorations on vases

by R Cowper

Hi, with great gusto and unthusiasm your comments on cobalt colorations. You should think seriously about hiring yourself out as a pre-buying expert you would make a fortune. Your comments were great, that is what I like about the Chinese ming thing, you learn something new every day but I must say I really do think the colours of vases and the like must lessen with the passage of time. Sun wind rain and the chemical combinations abounding in the atmosphere see to this. Even tomb objects I daresay would not be as bright as the day they were concieved 400 years ago. Actually I thought I did see a T.V. program which named this degenerative process. I also must say in passing that there is almost something indefineably attractive and alluring in Chinese pottery etc. It is much like a fever or getting bitten with the bug, exciting and adventuresome, neverending might be the word. By the way did you read the comment by Kenny on color varions.Lots of Kilns in Indonessia twenty years ago churnig out copies....I bought items from a Sulawasie

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Mar 29, 2011
by: peter

Interesting subject.
I would like to mention a few points for consideration.
1. We do not know the real colors when those porcelains were fired. So we have no way to compare.
2. If we talk about Ming, then we have nearly 300 years of development in ceramics. From beginning to end of the dynasty the clay was different, the white glaze was different. The white ground color was not always white, but rather gray at times.
3. Materials/substances used were different from kiln to kiln.
4. Transparent glazes were added relatively late. As they are vitreous, they may completely close off any atmospheric influences, like glass, but not heat or cold.
5. The blue pigments were of mineral origin, that is from quarries. These are less subject to change than organic or chemical components, which easily change in the light, etc.

>Sun wind rain and the chemical combinations >abounding in the atmosphere see to this.
Maybe...but why should they have been exposed to sun, wind or rain?

In ancient China most people could not afford any decorated porcelain. Those who had some used them for generations, not just a few decades or a lifetime. With bowls, dishes, plates, etc. a degradation is much more likely than with vases, because they were exposed to the food and were washed regularly.
Most Ming items known today would probably fall into one of three categories. (1) Family heirlooms or collection items well cared for, (2) excavated items, (3) shipwreck items.
The latter two are most likely to suffer from degradation, either to soil components or erosion. Items (2) could change the color due to chemical interaction of the pigment with the soil. (3) would result in diluted blue if the vitrous glaze was breached by the sand or saltwater. In fact, some shipwreck items are almost white.

I think if there is a color degradation, it most likely must come from the inside. That is, the pigment may get affected when the glaze or clay itself changes and allows external chemical components to come into contact with the blue. From what I know the blue pigments contain Mangan oxides and Iron oxides (Fe2 O3). I would see a possibility that there could be a change in these when other chemicals enter.
But, I wonder if there is sufficient research to prove that somehow?

If we look at the Qing dynasty blue and white and its glazes, made at least 250 years ago, we see that the blue is still very clear and shows no degradation. It could be, therefore, that any degradation in the Song, Yuan and early Ming periods were due to production techniques that were not mature yet.

Mar 28, 2011
by: peter

Hehe...from what I know Indonesian fakes are as good as the Chinese ones. Be careful...
With the many shipwrecks there they should have an ample range of originals for copying.

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