I make some researches on pure silica and smalt in pictorial coat from the XVI century. In the articles I read, I found mistakes of translation for example esmalte in spanish is some time translated in smalt in english. For pure silica the authors speaks about "Cristallo".
Can it be observed by EDS as a pure Silica only SiO2?
We also found a glass with many components Co, Mg, Fe, K.
I don't think it is a Smalt. Is it?
Hi Albert,
For qualitative or semi-quantitative work EDS is fine, but you won't be able to quantity as well with that technique as you will with others. I think you are asking about which techniques can be used to determine the composition of glass quantitatively: Inductively Coupled Plasma Spectroscopy (ICP OES or ICP MS), X-ray Fluorescence (XRF) and Electron Microprobe (EPMA). I wasn't familiar with the term "Smalt," but when I looked it up it apparently means "cobalt-containing glass" and is identified by its blue color. Typically, cobalt is added at concentrations of less than 0.2 wt% in my experience, as it gives a very intense color even at that concentration. EPMA is NOT suitable for quantitative detection of less than 0.5 wt%. ICP OES might be fine. If you don't have much experience with wet chemistry, I would send off the sample to be analyzed in an external academic lab. Penn State and Stanford, my two aluma matter, both have ICP facilities and glass science professors. Of course, most geology departments with ICP capabilities and rock crushing stations could do the analysis; I recommend two fluxes (Li metaborate and/or sodium carbonate) depending on which elements you believe may be present. Another option might be a pay-by-analysis laboratory.
Most glass contains elements other than pure SiO2. SiO2 melts at >2000 C, whereas soda lime silica glass melts at much lower temperatures. If your question is more 'what elements are normally in glass', I'd be happy to help, too. Good luck on the historical research.
Hope that helps!
Elizabeth
Edit: I just looked at your project. I'm not sure what "natural colorless" glass means. If you mean sand that was hit by lightening, you could get very pure SiO2 that way. I'm not sure what techniques ancient people had for melting glass, and I take back the comment on 'what elements are normally in glass' as I was only referring to major components in modern glass. Any d1-d9 transition metal might lead to coloration, so I'm kind of curious how ancient people excluded most transition metal impurities to arrive at synthetic and colorless glass? Even today, you'll see a green tint in many bottles because of iron impurities. Finally, if you aren't familiar with XRF, it can be done with or without sample preparation, similar to variable pressure SEM.
Dear Elisabeth,
Thanks a lot for your answer, You saw that I'm not a chemist, that's why my first question was a little melting-pot.
I looked forward and my questions found some answers.
Your answer insured me about the scientific way to establish quantitatively and qualitatively percents of element in the glass. I think now that the articles about glass may be moderated following the scientific protocol established. Some are an approach, some are real measurement.
For the "Smalt", the wonderful work of Marika Spring from the National Gallery of London 1 and Barbara Berrie from the National Gallery of Washington 2, gave me all the answers I needed.
For the SiO2 that we found, I don't Know, for now if it is some very pure sand or some glass. And the physicist with whom I work is like me.
This research about silicon in painting is very exciting. I hope it could be a good way to date the paintings in the future .
Sorry for my bad english.
best regards
Albert
1- Marika Spring, "New insights into the materials of fifteenth‑ and sixteenth‑century Netherlandish paintings in the National Gallery, London", 2017.
2- Barbara Berrie, "Mining for Color: New Blues, Yellows, and Translucent Paint", Article in Early Science and Medicine · December 2015.
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