You might have noticed that my blog posts are sometimes spurred by perceived errors or mis-statements in other peoples works. I think it important that criticism is made and better information disseminated, and since I don’t own a newspaper or TV station, I have to make do with this blog. Also it often helps refine my own thought and provides a spur to reseach. I have often changed my mind/ position on something after re-reading and researching the subject. I also find that I understand and think about things better when contrasting them with other ideas rather than in a vacuum.
Today’s example is in Rasmussen, “Advances in 13th century glass manufacturing and their effect on chemical progress”, Bulletin of Hist Chem, vol. 33 number 1, 2008. Which can be found here.
It summarises various bits of research suggesting that Venetian glass makers in the 13th century improved their recipes by the use of Levantine plant ash. The use of these soda and quartz glasses, low in P and Fe and with increased lime and magnesium, would, he says, have given improved capabilities to withstand chemical attack. This part of the paper is clear enough, and I have no great quibble with it, although I have not read the papers he references to back up the physical properties of glass with such Mg and CaO contents.
The weakest thing is that he quotes only 4 different analyses of glass from Venice, which is hardly a representative sample. They are from the 9-10th century and 11-14th centuries, and so whilst they do show a difference in composition, I am still rather wary. It has happened before that someone has promulgated something that is correct with the backing of insufficient evidence, or made statements which suggest a greater accuracy and precision in dating than is acceptable from the evidence adduced. A lot of what he uses is circumstantial, such as dates and changes in practise and use which are not well understood. So this paper is perhaps better understood as offering a theory with further work required to re-inforce it. Or so I think.