Hi Jim,
Fire gilding would be done after niello or enamel work. If you
were to take a fire gilded piece up to the temps of soldering or
fusing glass or niello the gold would diffuse into the silver and
depending on the temperature and time you will either have a very
green gold surface or no visible gold left due to the gold having
diffused into the bulk silver below it.
I would never recommend fire gilding without lab conditions.
there is info at ganoksin:
I did it a lot at one time as a youth (phew I’m still here), maybe
50 or 60 times, and got good at it.
It is very controllable, and the gold is thick. My experience was
that the gold would take very high temperatures without any absorbing
into the silver, though I agree you could play with very thin layers
and diffuse them into the silver to get greenish alloys. I would do
niello last of all in such a procedure, but I think you might get
away with enameling onto a fire gilt surface.
I spent years learning to emulate the effects of fire gilding to
avoid doing it, as I now consider is unnacceptable. Keum boo is very
effective for certain looks. Marne Ryan has approached it in her
fusing of 18k onto sterling. Flame fusion (metalizing) and vapor
deposition (can be done by anyone with access to a scanning electron
microscope) work well.
keum-boo info here:
Here is a quote from my 1986 paper on gold application alternatives
to fire gilding;
In the past I have used an valued fire-gilding as a way of
placing gold metal surfaces. There are however other ways of
obtaining similar effects and in the light of today's knowledge
of the toxicity of mercury this is a totally unacceptable
procedure except under stringent, appropriate chemical lab
conditions. It is worth mentioning Mark Stannitz who did
research on mercury gilding at RIT with proper lab conditions
and gave it up as he could only obtain 95% recovery of the
mercury used and felt this was too much unaccounted for. In
1987 when delivering this paper to the SNAG conference I
approached Walter Soellner whose account of mercury gilding is
the Untracht book. I wished to apologize as I intended to
criticize his procedure (admittedly the best of any
published-still unacceptable). His response was "Good I don't
do fire gilding any more, its too dangerous...."
Fire gilding involved the making of an amalgam, a mixture of
gold and mercury. This mixture is a complex one involving
mechanical mixing, chemical bonding, alloying and dissolution.
The heart of the process is that mercury 'wets' the gold.
Wetting is what detergent does to solutions and greases.
(Gmelin, pg 289). Excess mercury was removed from the amalgam
by pressure leaving about 40% of the remaining amalgam as gold
(Gmelin pg 283). The amalgam was placed on the work and
evaporated with heat to leave the gold behind as a deposit to
be burnished as it has a rough, porous texture after firing.
While all stages up to the evaporation of mercury may be done
under water (even this is not described in the literature) to
minimize exposure the last heating stage is the part that
releases mercury in volume.
It is fair to say that all published accounts I have seen on
mercury gilding are unsafe, some downright dangerous. In some
cases no safety warnings at all are given (Diebeners, pg20) or
its down played in statements such as "For enameled pieces,
mercury gilding is less dangerous than electro-plating with its
strong current." (Seeler, pg 79). Many accounts of procedures
described in contemporary sources are virtually unchanged from
versions recorded in Roman times or before as early as 700 BC
(Gmelin pg 38). This is despite changes in knowledge of what
mercury does to the body. It's effects include emotional
stress, severe trembling, loss of muscle control, slurred
speech, personality changes, osre gums, loose teeth, blurred
vision (Quin, Stock, Pg20), lung and kidney damage (Untracht pg
667) and often permanent damage to the central and peripheral
nervous system (Quin, Stock, pg 20). Death can be a result of
mercury poisoning (McCann pg 16). I have recently been informed
that mercury has a half-life in the body of sixty days or so
(Canada Safety Council pg 1333). Low level exposure (no one
seems quite sure what low level would mean in fire-gilding)
will eventually leave the body to a great extent. Repeated or
high exposures build rapidly to really toxic levels. When
fire gilding mercury condenses on tools, vent hoods, walls etc
and re-evaporates at room temperatures creating a slow and
constant exposure. The health effects were noticed in the
past. The Incas banned the extraction of mercury and Cellini
wrote "Gilding should be left to those whose vocation it is to
do it, as it is..... extremely damaging to the health. The
Master is satisfied to know the procedure and with the-Basta:
(Cellini, pg 96). Goldsmiths are often restricted in their
thinking by tradition and mercury gilding procedures are a case
in point. The descriptions are unchanged in hundreds, even
thousands of years. It is possible that with research a safe,
laboratory procedure may be developed, possibly by replacing
the mercury with a non-toxic material which is removed leaving
a powdered or flake 24k gold on the host surface to be
burnished down. At the moment however there are alternate
procedures described in this paper which can give similar
results without danger from mercury. It was partly a search
for such alternate procedures to mercury that led to writing
this paper.
Some at ganoksin:
and an article on doublee at:
http://www.silversmithing.com/1doublee.htm
best
Charles
Charles Lewton-Brain/Brain Press
Box 1624, Ste M, Calgary, Alberta, T2P 2L7, Canada
Tel: 403-263-3955 Fax: 403-283-9053 Email: @Charles_Lewton-Brai1