Series editors' preface - Wood Tools

and graphite. They were commonly used on
cast iron domestic objects such as stoves,
grates, fenders, hobs etc., and gave a shiny
black polished surface. These products were
common in the nineteenth and early twentieth
centuries and are still available in the UK (e.g.
Z-Brite).
After the introduction of electroplating in
the 1840s, a variety of metals were plated onto
iron. Chromium and nickel plates were
especially popular for iron. Since relatively few
metals will plate onto iron, it is common to
find a copper layer, which is easy to deposit
on iron, underneath the surface metal plate.
Modern tin electroplating replaced the older
method of hot dipping in molten tin. Mercury
gilding (fire gilding or amalgam gilding) can
be done on iron that has first been coated
with copper, which was usually done by
boiling in copper sulphate or ‘blue vitriol’.
Electrochemical gilding using cold gold
solutions (gold dissolved in aqua regia, a
mixture of nitric and hydrochloric acids) were
also used, but gave only a very thin gold
‘wash’ that was easily abraded.
Japanned coatings for iron were black
pigmented, baked-on (stoved) oil-resin
varnishes. Japan coatings were popular on
sheet iron and tinned iron as a base for
polychrome and gilded decoration, and on
utilitarian iron objects such as tools, boxes,
hardware etc.
Tin has been a common decoration or
overall coating on iron from ancient times to
the present. It is shiny and more resistant to
corrosion than iron, but unlike zinc, it does
not confer cathodic protection to the iron, but
protects it only as long as the tin layer is
continuous. Tinned iron is commonly referred
to as ‘tin’, and has been used extensively to
make decorative and functional artefacts since
the eighteenth century.
Galvanizing is the term for a protective
coating of zinc on iron. The zinc will be
preferentially corroded as long as there is any
metallic zinc in electrical contact with the iron,
and so does not rely on a continuous barrier
layer.
Various metallic compounds have been used
extensively as paint pigments or as primers
where another colour is coated on top of
them. Red lead (Pb 3O 4) has been used as a
protective paint for iron.
Conserving other materials I 689
Mechanical removal of corrosion
products
Mechanical corrosion removal methods are
commonly used to remove corrosion products
from ferrous metals. It is helpful to establish
whether the corrosion problem is one of small
areas of corrosion that have generated a large
amount of products or whether surface as a
whole has suffered. The least interventive
methods should be tried first. The use of a
sharp tool to pick away flakes is appropriate
for small discrete areas of corrosion. Where
possible this should be undertaken using
(a)
(b)
Figure 15.9 Removal of corrosion products
(a) Detail of a quoit from a ceremonial Akali (quoit)
turban, mid-nineteenth century, Punjab, India, before
treatment. Gold wire overlaid on blued steel. Ferrous
corrosion products were present below, beside and over
the gold decoration. (b) Detail of quoit after treatment.
The gold was pre-consolidated with Paraloid B72 to
prevent further loss. Working under magnification,
ferrous corrosion products were removed from on and
around the gold using a scalpel. The turban was coated
with three thin applications of microcrystalline wax after
treatment