|Monthly Tech-Tip |
These side-by-side recipes show Insight-Live calculating the oxide formula, chemical analysis and calculated thermal expansion of a recipe that uses soda feldspar (on the left) and potash feldspar (right). The soda feldspar one should calculate to a higher thermal expansion, because Na2O has a higher expansion than K2O, right? But notice it is only 7.1 (vs 7.4 for the potspar version). Why? It is the amounts: The K2O version has a total of 4.33% KNaO whereas the Na2O version only has 3.05%. However Insight-live also calculates the COE based-on-molar (shown below the others). It that case, the sodaspar does have a higher COE, 7.2 (vs. 7.1). Some technicians believe thermal expansion should be calculated based on the weight%, others based on the molar%. You have to decide.