I've owned and fired L&L kilns since the 1970's. They just keep getting better. I have 2 in my studio and 4 in our college studio.
William Schran is the Assistant Dean Fine Arts at Northern Virginia Community College in Alexandria Virginia. Bill has been working with Crystalline glazes for decades and presents at many forums and cares deeply about the entire arts community. Bill teaches what may be the only semester long course in cone 6 crystalline glazes.
Here is what he says about his research:
"Though traditionally produced at cone 10, I have discovered very satisfactory results with crystalline glaze formulas fired at cone 6. My research in this area started as a result of the kilns at school not firing to cone 10 quickly enough to allow time for necessary temperature holds to grow the crystals (this was before we had all L&L kilns). I experimented with existing cone 10 recipes by adding increments of low temperature fluxes until I found a few newly formulated glazes that produced consistent results. I’ve continued this area of research, concentrating on glaze formulas using various commercial frits as the primary flux. The results of this research will provide studio ceramicists and schools with limited firing capabilities the opportunity to explore crystalline glazes."