Hi John


If you are simply interested in the range of glaze color in the British refined earthenwares from circa 1770 - 1830 or so, you are more than welcome to visit sometime and I can give you a two-hour overview of the variables related to that issue before you begin your colorimeter recordings.  While George has spent many years researching that period, I have spent almost the same amount of time documenting extant China glaze examples from this long period of time to better understand the evolution of the decoration, identify manufacturers, and understand stylistic changes.  


Beyond our articles which George has given the references, the new books by Lois Roberts are essential to anyone who is interested in the evolution of China glaze.  Science and machines have their place in analysis...certainly no one uses XRF and other techniques more than I do for ceramic research issues...but  the basic techniques of connoisseurship-the experience that comes from hands-on observations also have a place.  Sadly, these more intuitive approach are  rarely included in today's archaeological curricula.


Some snaphots of these "snowflakes" (that is, no two alike) may be of some use:  


http://ceramicsinamerica.blogspot.com/2012/02/color-variation-in-british-china-glaze.html  


Please note these selected examples represent approximately 50 years of British ceramic production, numerous manufactures and every example pictured (there are many, many more) has a slightly different color.  


Rob