MITRA Forum Question Details

I cannot answer all of these points but will weigh in on what I can and send the others on to others. First as to terminology, my resources say one word: metalpoint. As to your question about the use of whiskey to speed up oxidation. I do not believe that this would have any real contribution. The ethanol portion would be reactive to the metal than plain water. I do not believe that any components in the oak casks associated with aging the Whiskey would reach the metal but I guess that perhaps the tannins could theoretically have a tiny effect, but I doubt it. Others may have opinions that are more concrete on this. I hope that some of our paper conservators and scientists can comment on your other points.

BTW, you would probably have interest in this recent publication.

https://www.archetype.co.uk/publication-details.php?id=239

​Hi Koo, I don't believe that short-term exposure to liver of sulphur (a varying mixture of potassium sulphides) would necessarily cause any detrimental effects to a paper-based support; in fact, liver of sulphur was used to tone black and white photographic prints around the turn of the 20th century.  Due to the fact that this substance is alkaline, I also don't think that short exposure would be problematic for an acrylic ground.  I'm not sure how it might affect a wood-based panel support - perhaps someone else could weigh in on that one. 

​There is so much to think about, here. I don’t know whether Ag2O looks different that Ag2S, but I think that sulphur is never a good idea.  I wonder whether the Ag2S would be stable, or could continue to react, with atmospheric gases. I think that the sulphur would be bad for the paper, and may react with the acrylic, in either sheet or dispersion. Ultimately, I think that keeping thing as chemically simple as possible is always the best path to stability. If enhanced oxidation is really needed, I would be least uneasy with exposure to H202, since it brings only H and O, to the party, but it would have to be in a gaseous form, for my comfort, and I have no ideas whether this might work. Blowing on the image would bring it CO2 and any biologicals that might be expectorated, with the blows, and I would imagine that all would probably be a source of oxidation. 

Hugh Phibbs

While I do not know with absolutely certainty, I suspect that hydrogen sulfide (that rotten egg smell) evolves from by a liver of sulfur solution.  Hydrogen sulfide is a common ingredient in air pollution.  As an oxidizing agent, it is corrosive – which is why it tarnishes the silver in metalpoint drawings and darkens lead white pigments (now prohibited for artist's use).  Conservators see darkened lead white (lead carbonate converted into lead sulfide, usually resulting from exposure to air pollution or the VOCs emitted from plywood) pigments quite often in old master "heightened" drawings, in illuminated manuscripts, and, also, around the edges of the preparatory grounds for metalpoint drawings. However, oxidizing agents also attack the double bonds of cellulose, accelerating the symptoms of paper aging, such as brittleness and yellowing.  As a paper conservator, I cannot recommend the exposure of paper to hydrogen sulfide.  At the same time, we do not know how much exposure to hydrogen sulfide (how long, what concentration) is required before meaningful (greater or faster than "normal") degradation takes place. So a pragmatic approach would be to expose the drawing until you get the results you want and use a good quality, sufficiently sturdy, and toothy paper as the support for the preparatory ground.  

As to why whiskey breath would accelerate tarnishing of silver, I cannot say – must have been something he ate!

- Margaret Holbein Ellis

​Thanks for the update Koo...

Koo

That is great. I would certainly expect this effect considering the thiols in those vegetables, although I have not heard of anyone accelerating the darkening of silver using produce. I have often joked with my students who are bothered by the paleness of their metalpoint attempts that we should make a sulphur chamber to speed up the process. I guess that I will suggest refrigerator refuse in the future ;)