The successful introduction of kaolin clay stimulated the
testing of further mixtures, corresponding to the samples P80BC
and P70B-C, in which soda-lime–silica glass was replaced by
pharmaceutical borosilicate glass. The replacement was mainly
aimed at evaluating the impact of a glass with a much lower
content of CaO. Fig. 2 and Table 3 show that the change in the
secondary glass had an important impact on the crystallisation:
borosilicate glass greatly promoted the formation of anorthite–
labradorite, with a dramatic decrease of the peak associated to
melilite.