The nature of glass-water interactions is complicated at best. Understanding these interactions and developing a predictive model is more difficult for complex waste containment glasses than for relatively simple glasses such as those typically reported in the literature. A common method of obtaining leach data is to use powdered samples. This procedure often gives results that cannot be used to predict the leaching characteristics of solid glass samples. This is due primarily to the pH differences encountered in the two types of experiments. Additionally, the effect of gamma irradiation, which is present in actual waste containing glasses, is to enhance the leach rates of most elements in the glass. Other parameters that affect leach rates and which must be incorporated in a predictive model include back reactions, solution flow rate, solubility limits, temperature, time, pH, and sample surface area to solution volume ratios.