The erasers that we’ll be using for protein extraction on the manuscript are Mars Plastic 526 50s, which are white vinyl erasers composed of polyvinyl chloride (PVC) and a calcium carbonate filler. Many online sources also claim that they contain a phthalate plasticizer, which I found entirely reasonable because PVC is super rigid and really needs something to reduce its Tg and make it softer/generally more eraser-like. Little did I know what I was getting into, however, because here’s where the mystery begins: the Mars manufacturer, Staedtler, proudly asserts on their website that these erasers are phthalate free. Well, shit.
So basically I ended up actually calling the Staedtler US headquarters and talking to a very nice woman who had absolutely no idea what I was going on about. I was redirected to the Canadian headquarters where I could try and connect to a product manager (shout out to Diane, who I never had the chance to chat with), but it was pretty clear that I wasn’t going to get any specific info. Suspicious, I’d say. I then happened across a forum post from 2012 in which an art conservator noticed that the erasers smelled different from what she was used to (Mars Plastics are used widely in this field to clean old stuff). Perhaps all my online sources were just outdated, and the modern Mars erasers are really phthalate-free?
Allison and I definitely couldn’t leave this well enough alone (obvi) and so hacked a Mars eraser to pieces and took an IR spectrum. Phthalates have ester bonds, and so if the eraser was phthalate-free then it shouldn’t have had any peaks in those C=O and C-O regions. But, they were there! Our only guess at this time is that her eraser is super old and differs from the current manufactured products, so it’s kind of a cold case atm.
Despite all that business, we did get around to actually talking about why the eZooMS method should work – it all comes down to electrostatics, which makes 200% sense when you look at the structure of PVC and of collagen. Dipoles away! We also talked about future plans, which are going to involve me learning about Raman spectroscopy and perhaps the both of us figuring out how to work the Confocal.