From: owner-scribes@castle.org (scribes digest) To: scribes-digest@castle.org Subject: scribes digest V5 #79 Reply-To: Sender: owner-scribes@castle.org Errors-To: owner-scribes@castle.org Precedence: bulk scribes digest Wednesday, March 14 2001 Volume 05 : Number 079 ======================================================================== To unsubscribe from this list, send email to with unsubscribe scribes-digets in the body of the message. Leave the subject line blank. Do not include any additional text. Re: [scribes]: Sulfur interactions... Re: [scribes]: Sulfur interactions... ---------------------------------------------------------------------- Date: Tue, 13 Mar 2001 19:42:40 +0000 From: Catie Helm-Clark Subject: Re: [scribes]: Sulfur interactions... Bryan Bell wrote: > > >Theresia wrote: > >the sulfur can react to form PbS, which is the black mineral galena. > > Lead sulfide (PbS) is an actual compound (in addition to being what the > mineral galena is primarily composed of--any mineral also having traces of > other elements within their lattice structures). I think it would be > better science to think of the PbS as a coating or powder, so to speak > [snippage here] > So we're not getting galena crystals actually growing, but rather lead > sulfide is being formed from the conversion of the lead oxide (PbO). It took me a minute to realize that you were thinking like a chemist. Molecular structure, not macroscopic "habit," determines if it's a mineral - if you're thinking like a mineralogist, that is. Trace element composition does not change the overall lattice, so a mineral is still a mineral regardless of trace elements. Therefore a coating ("effervescence" in mineralogy-speak) is still a mineral, as is the pseudomorphic substituion of lead white by PbS within the paint. But this is really just splitting hairs... ;-) The reason I mentioned galena is that some people who are neither mineralogists nor chemists will still recognize that PbS/galena is a black mineral (the color of the alteration), thus making the the discussion of the alteration chemistry of the paint perhaps a little more comprehensible to non-specialists. > >Vermillion is the hexagonally symmetric form of HgS. For reasons still > >not clear, it > >can spontaneously rearrange itself into the cubic form of HgS which is black. > > That is quite interesting--I'd like to find out more about that chemistry. > I won't bore you with my thoughts on why, which have to do with icky, > tedious stuff (well, fun for me) like electron structures and coordination > chemistry... > Your resident chemist at large, > Bryan (mundane) You will find the scholarly discussion of vermillion alteration in: Artists' Pigments A Handbook of Their History and Characteristics Volume 2 Edited by ASHOK ROY, National Gallery, London Oxford University Press isbn 0-89468-260-1 This is actually a three volume set covering just about every important historical pigment. They cover chemistry, provinence, usage by location, artist, and historical period. So throw your Daniel Thompson away, he's been superceded (he also incorporates some "mistakes," especially in his discussion of yellow pigments and in his redaction of Ceninni's recipe for gesso) You may be also interested in scoring a copy of _The Physics and Chemistry of Color_, by K. Nassau, 1983, John Wiley & sons. He goes into some of the alteration chemistry of paints going bad, as well as a detailed discussion of why certain inorganic pigments are better than others (eg, lead white vs "whitewash" (calcium sulfate or calcium carbonate)). There's a new edition of this book coming out any day now, so it's probably wise to wait for it rather than hunt down the 1983 version. I don't recommend this book to non-chemistry nerds, but if you're into, for example, ligand theory, this a book for you. The book is also _not_ paint pigment specific: Nassau discusses the paragenesis of all color effects, including iradescence, coloration of plants and phosphorescence to name a few. ttfn, Therasia ___________________________________________ Reward doubled in Abernathy murder case http://www.onewest.net/~no1home/index.html =================================================================== To unsubscribe from this list, send email to with a blank Subject: line and unsubscribe scribes in the body of the message. Do not include any additional text in the body. ------------------------------ Date: Tue, 13 Mar 2001 19:07:17 -0800 (PST) From: Bryan Bell Subject: Re: [scribes]: Sulfur interactions... >Therasia wrote: >It took me a minute to realize that you were thinking like a chemist. >Molecular structure, not macroscopic "habit," determines if it's a >mineral - if you're thinking like a mineralogist, that is. Point taken, m'lady...I just had to chuckle though when you mentioned galena, because I immediately had this vision of someone watching through their glass frame for something akin to rock candy (I know, bad analogy) forming on their prized piece of illumination. That's why I thought it would be easier to describe the PbS as a powder rather than what you very rightly said was a mineral (in mineralogist terms), which I liken more to a rock (ah, that's why I'm a chemist and not a mineralogist LOL)... >(Snippet) >You will find the scholarly discussion of vermillion alteration in: Ohhh goody goody! :) I can't wait to get my hands on the two books you mentioned, Therasia, yes, I was thinking of ligand chemistry and other complexes--really loved inorganic chem in undergrad and grad studies! (In fact, this is way off the subject, but one of my real interests with inorganic back then was extensive literature research I did on using organometallic ligand complexes in cancer treatment--would love to chat with you on it some time if you're interested, off the list.) Gee, I feel like a real nerd now...LOL Bryan (mundane) =================================================================== To unsubscribe from this list, send email to with a blank Subject: line and unsubscribe scribes in the body of the message. Do not include any additional text in the body. ------------------------------ End of scribes digest V5 #79 ****************************