||Coalbrookdale gates to St John’s Church, Devizes:
the ironwork needed repairs after suffering a vehicle
strike (above right). The gates and piers were removed
to the workshop where new internal strengthening
frames were built to support the fragile cast iron.
One of the pier caps had a piece broken out of it which
was repaired by setting in a new piece of cast iron
moulded to the original profile. The three-coat paint
system used comprised a high solids, epoxy aluminium
primer (Protegabond ST200); two-pack, high solids,
epoxy intermediate coat (Protegabond WG500); and
two-pack, re-coatable, aliphatic polyurethane mid-sheen
finish coat (Protegathane PLS(HS).
From modest rural chapels to grand
urban churches, historic places of
worship of all sizes have railings and
gates in wrought or cast iron. Iron window
frames are also common. All require routine
maintenance including regular painting. Paints
not only enhance the appearance of ironwork,
they provide vital protection from corrosion
by serving as a barrier to air and water.
CHOOSING A PAINT SYSTEM
In this context, the term ‘paint’ is actually
shorthand for ‘paint system’, meaning a suite
of paint products from primer through to final
coat. A paint system might be a traditional
lead- or oil-based type, or it could be one
from a family of modern synthetic products.
The repair and maintenance of historic
fabric should normally be carried out
using historically authentic materials, but paint presents some difficulties here.
Lead-based paints, which were used widely
for generations, offer excellent performance
and have a distinctive sheen. However,
environmental legislation has prohibited their
use except on scheduled monuments and the
most important listed buildings (Grade I and
II* in England and Wales, and category A in
Scotland). Permission to use them may be
obtained by application to English Heritage
or its counterparts in Scotland and Wales
via one of the few remaining manufacturers.
Applications must include details of the
planned use and quantity needed, although
the latter can be difficult to estimate when
painting elaborate wrought iron railings and
gates. Procurement can be a lengthy process.
Other traditional oil-based paints
are widely available, typically containing
titanium dioxide rather than lead. They dry
slowly to a film that remains soft for some
time so newly-painted items can be difficult
to handle when they are transported from
workshop to site. Painting on site presents
less of a problem but adequate drying times
are needed to prevent mating surfaces
from sticking together (for example, where
gates meet or metal windows close).
Modern paint technologies have a lot to
offer. The coatings that make up a particular
paint system can be relied on to work together,
physically and chemically. Manufacturers
provide specifications for preparation, film
thicknesses and methods of application so
that a quality result is assured. Each coat
cures quickly and adheres firmly to the work.
However, the most powerful argument for
using a modern paint system is durability
– some two-pack paint systems have a
projected lifespan that exceeds 25 years.
COLOUR AND SHEEN
||The gate posts in the workshop of Calibre Metalwork (above left) after blast cleaning and priming with an epoxy
aluminium primer; (above right) after repair and with the two-pack, high solids, epoxy intermediate coat applied,
and (left) the final coat showing the subtle reflections of a mid-sheen topcoat (an aliphatic polyurethane)
Analysis of paint samples taken from ironwork
can be used to identify previous colour
schemes. The results need careful interpretation
to differentiate between the colours of
undercoats and topcoats, and to allow for any
yellowing that may have occurred in the oil
medium. Whether or not there is any intention
to replicate historic colours, the analysis
provides a valuable historical record which
would otherwise be lost to paint stripping.
Some of the older paint technologies
are limited in colour range. A colour palette
contemporary with your ironwork can
be researched to assist with selection.
Given a free choice of colour, specifiers
tend to ask for black with gold highlights before
giving the matter any real thought. Subtle
greens, rich maroons, and warm browns can
look very distinctive in both urban and country
Whatever the decision, it
should be made in plenty of time. Undercoats
are toned to support the colour of the final finish
and workshop painting begins earlier than many
people realise. Painting should not be rushed.
Sheen levels also affect the overall
appearance. The surfaces of hand-forged
work do not have dead flat surfaces, so
a high gloss finish looks wrong. A mid-sheen
finish produces a better result on
wrought and cast work. Oddly, project
specifications often fail to mention sheen.
||Applying the finish coat to refurbished cast iron
railings at 107 Great Mersey Street, Liverpool: the
paint system used here is Protegabond ST200 two-pack
epoxy aluminium primer and Protegathane
PLS(HS) two-pack re-coatable aliphatic poly-urethane
in graphite black with mid-sheen finish.
Preparation depends on where the work is
to be done. Ironwork that has deteriorated
badly or has been accident-damaged, usually
requires full workshop facilities. This enables
the blast-cleaning, repairs and painting to
be undertaken in controlled conditions.
Repainting ironwork in situ, when
practical, saves disturbing associated masonry.
It can save on cost too but it may not be
a sensible longer term option if water has
penetrated inaccessible areas. This might
show as damage to stonework caused by the
expansion of rust. Removal and thorough
treatment is the only long-term solution. Mobile blast cleaning services can remove
old paintwork on site, but method statements should be checked to ensure that adequate
masonry protection is put in place as well as
any necessary noise and dust control measures.
There is a case for not removing old paint if it
is well-adhered to the iron, although knocks
and chips in a heavy build-up of old paint
are difficult to flatten out by local treatment
with abrasive papers. While some surface
variations contribute to a sense of history and
age, old chips that are too prominent beneath
a new paint layer leave everyone dissatisfied.
Painting is a skilled job which is easy to
underestimate. No matter how skilled
the metalworking element of a project,
most people will judge the quality
of the work by the paint finish.
For on-site painting it is a sensible
precaution to allow a little extra time to
allow for unsuitable weather, be it cold, rain
or both. Wet paint that has been rained
on will show blemishes. The only cure for this is the application of another coat.
Ironwork ought to shed water whenever it can be engineered to do so. Leaves and scrolls
in wrought ironwork make it particularly
vulnerable to water-trapping. Careful use
of lead putties to fill pockets will reduce the
problem. Epoxy fillers are used to seal joints.
Spray applications produce the best results
in the workshop. Smaller one-off items tend
to be brush-painted. Two-pack paints must
be mixed in the correct ratios and used before
they ‘go off’. It is this chemical reaction that
produces the fast-curing characteristic, enabling
work to be handled soon after painting.
|It is important to achieve an even, continuous coating
with the brush.
For paint to perform as an effective barrier
it must flow over the work to form a continuous
wet film of the correct thickness, and it will
then dry as a continuous protective coating.
A poor spraying technique will produce patchy
results. If a paint film is too thick it will tend
to sag and run. A spray gun held too far from
the work or used in short blasts will cause
the paint to hit the surface ‘dry’ producing
a rough surface that has no film continuity.
Skilled brushwork will produce the continuous
film required without patchiness, runs or
drags. Small rollers may be used on palings.
Paint ‘misses’ are avoided by using
different shades for each coat (for example,
an off-white undercoat for a white topcoat).
Specifications sometimes set out the shades
to be used for each coat so that they can be
readily identified for inspection and approval.
Film thicknesses can be measured
with equipment ranging from simple
pocket mechanical devices through to
sophisticated electronic instruments such
as those manufactured by Elcometer.
During on-site painting it is important
to ensure that adjoining surfaces are properly
protected. Where ironwork meets masonry,
the latter should be masked off. Method
statements should state how general fabric
will be protected (not simply that it will
be) and how spills would be addressed.
Finally, there are a few simple measures
to keep new paintwork in good order:
- Provide for repair or replacement of locks
in specifications for gates, including the
number of keys required. This eliminates
the need for chains and padlocks which
can quickly damage paintwork and look
- Consider how gates are to be held open.
Various types of holdback latch can be made
and installed with the refurbished gates.
- Gates may need adjusting at the hinges
from time to time so they close correctly.
Address this promptly should the need
- Inspect all ironwork annually and touch-in
any paint chips and scratches with
an appropriate product. Clear away any
vegetation (ivy growth, leaf debris) that
might prevent ironwork drying out after rain.