I read with interest your article on authenticating Tang pottery without TL test and I would like to share with you my experience on what I did before and after reading your article.
After fumbling along for sometime searching for a method to assist in my purchase of authentic pottery of Tang and earlier made, I had on one occasion bought a small damaged old looking horse (10" x 12" with the look of a Wei or Qi horse) and had it washed and stripped off all its whitish strip and remaining pigment just to see what is beneath the surface coatings. As I was hosing down the pottery piece, a very acidic pungent smell filled the air. I was surprised but did not know then what the smell was and where it came from. I had the washed horse now in complete dark grey color, dried, ready for further study.
Further, I attached herewith photos of 2 pieces of pottery bought with the assistance of your suggested tests, particularly the water soaked test. I request that you review these photos and let me know your expert opinion as to their age. My belief is that the horse is of the Wei period and the beast of Han made.
Regarding the reason why a spot becomes dark, that is just a question of light reflection and thus indicates that the clay is very porous - as it should - if it is fired in an old low temperature kiln. We can only guess and use our best judgment, but if it passes the "soak test" and looks all right, it most probably are, all right.
From experience I would like to say that I think the beast (top figure) looks ok and as it should. There are something with the wings though, that I don't understand. Maybe that section is repaired?
Regarding the horse, I can only say that it looks strange in my eyes. I think the entire horse looks like it has been sculpted out of a block of hardened clay much rather then having been modeled in wet clay, as usually was the case. The head, the feet, the saddle, the high neck - all looks very strange.
I can only say that don't recognize it. This could be a fault of mine not being enough experienced, but I though I should just mention what I feel. One thing that is made at some fake factories, is that figures are actually sculpted out of Han tomb bricks. If so the clay will be of a Han date an test correct in a TL texst. The figure will be new though. Friends of mine have told me they have seen mounds of Han bricks awaiting to be processed into something, outside these factories.
If that could possibly be the case here I don't know, but in that case it should be visibly as broken bubbles in the surface.
Thank you for your interest.