Hi Peter, I have a small vase that has a spurious kangxi mark and a crackle glaze, I have talked to experts about the crackle glaze and when it first appeared on Chinese porcelain, I have talked to two experts and your self, both of the experts said that the Kangxi period did not have a crackle glaze period, I have several vase with a crackle glaze and they are late ching to early republic. Do you know when the first crackle glazes were made?
In the Song dynasty Ge wares and some Guan wares were specifically made with crackles as decoration. That is the earliest occurrance I know of.
Qing dynasty and othere later crackle items are generally called Fang-Ge wares, which means that they imitate Ge wares.
http://www.chinese-antique-porcelain.com/song-dynasty.html
http://www.chinese-antique-porcelain.com/glaze-crackles.html