[Sca-cooks] On Acid etching

[Alma Johnson]

> Have you done acid etching using period methods on different materials or
> different art forms? Metal perhaps as well as eggs? I think an overview
> article on period acid etching of different materials or how it was used
for
> different crafts would be interesting. We have discussed making vinegar
here
> before and how the period stuff might have differed in acidity. Was
vinegar
> the only acid solution they had available and used? I'd certainly like to
have
> a good article on these subjects for the Florilegium. And/or it might make
a
> nice arts & science project.

Stefan,
    I have done lots of etching on silver brass, steel and glass.  Primarily
hydrochloric, nitric and sulfuric acids and mixtures amongst these were and
are used for metals (aqua regia is one such mixture for etching gold) and
not glacial acetic.  I will be happy to share more information off this
list.

To Phlip, strong acids and bases look very much on paper as you said.  The
same sort of thing only coming from two different directions.  In practice,
however, they are not at all similar in the materials they will react with
and how they react.  Strong bases (alkali, caustic, however you call it) do
not etch metals like the acids do.  Think about it.  Metals(+) and acids
(H+) vs metals (+) and bases (OH-).  Totally different reactions, totally
diferent products.

To Adamantius, the vinegar (acetic acid) is leaching the calcium from the
eggshell.  Calcium is chemically  a metal, or cation (CA++) (it's just like
dissolving pearls in wine- the acidity of the wine is sufficient to react
with the calcium in the nacre of the pearl, dissolving it - a helluva way to
get your calcium!)

Class dismissed :-P
Rhiannon Cathaoir-mor