Ball Clay

Two versions of my cream glaze,same clay,same kiln,different ball clays. The difference is more striking in reality - the left ,more yellow version is what I'm looking for; I realised [or suspected] that the reason I had not been getting good results with this glaze [one of my two standard glazes] recently was a change in throwing clays [same firm, same clay,differing amounts of iron] - with the new batch,we're back on track. I experimented with a different ball clay in the glaze to see if this would solve the problem,but see from this first firing that the old glaze works fine with the current clay. In the process,I was reminded of the differences between varieties of ball clay,which I used to think of as a fairly homogenous material. this particular glaze seems to need a ball clay with a higher iron content - Puraflow rather than Hyplas,for the experts.