I’ve had a document in my files for a few years and thought it might
inform the debate on firescale-resistant alloys. This PDF
http://www.ganoksin.com/gnkurl/1t6 contains the results from a 2006
test carried out at the independent CATRA testing facility in Great
Britain. It seems to me, from these results, that reducing germanium
may not reduce firescale significantly. However, because of the
addition of zinc, there may be a change in the color of the firescale
that may not be so easily noticed.