The scarcity of archaeological evidence for Roman glass-making facilities has resulted in the use of chemical compositions as evidence for production models,[14] as the division of production indicates that any variation is related to differences in raw glass making.[11] However, the Roman reliance on natron from Wadi El Natrun as a flux,[13] has resulted in a largely homogenous composition in the majority of Roman glasses.[13][15] Despite the publication of major analyses,[16] comparisons of chemical analyses produced by different analytical methods have only recently been attempted,[14][17] and although there is some variation in Roman glass compositions, meaningful compositional groups have been difficult to establish for this period.[11]