We have test-used a number of glass gaiwans, many of which popular in online stores, and have found none satisfactory. Their relative clumsiness for handling aside, the resultant tastes from them have been inferior to those from simple porcelain ones. That’s why we always recommend against the use of glass gaiwans. They are good only for photo purposes. Teapots made with thicker glass, however, are okay.
For details of the criteria in selecting a gaiwan for gongfu infusion, please visit:
This video details well also the reasons for detail criteria of the gaiwan:
FYI, although we recommend strict criteria in selecting a gaiwan, those meeting such criteria are not rare, nor necessarily expensive. Some are in fact much more affordable than glass ones.
