I wanted to comment on a post on the HSS Forum for Visitors, open
questions, but it seems one has to actually be a member in order before
one can post anything to the visitors section, which seems fairly
counter-productive.

So I thought I'd post my comments on the use of gold paint on vellum
here instead.

Unlike iron, which is a ferrous metal and therefore prone to rust, fine
gold, which is available as traditional gold leaf or as fine gold
particles suspended in a medium like water colour, gouache or acrylic,
which can be applied with a brush, does not rust or tarnish. Pure gold
is inert and permanent. It does not tarnish or change its colour in any
way. Gouache is one of the most permanent of mediums. The best gouache
and acrylic mediums are usually very stable and do not yellow with
time.

Tablets of real gold water colour are available from well stocked art
supply shops. It is the equivalent of "shell gold", which is referred
to in old artist's recipes and formulas. It is and always has been used
for very thin lines and small illuminations but does not have the
continuous metallic surface necessary for use on large areas unless it
is burnished.

To make your own: Dump a book of gold leaf into a glass mortar with
honey and grind to a smooth paste with a glass pestle. Wash out the
honey with several changes of hot water, with a similar action to
panning for gold. Allow the gold to settle each time before you pour
the water out. Finally dry the remaining gold on filter paper and then
mix it with a weak gum solution. It can then be used on paper or
parchment as it was in  illuminated manuscripts, and can be burnished
to the highest brilliance using a amall polished agate.

I hope this will reassure anyone who has been surprised or concerned by
the inclusion of "gold paint" on Letters Patent.

If anyone would like to know a recipe for making your own gum solution
as well I would be happy to supply it.