Page 43 - Historic Churches 2013

BCD Special Report on Historic Churches 20th annual edition 43 CATHEDRALC O M M U N I C A T I O N S
The gate posts in the workshop of Calibre Metalwork (top left) after blast cleaning and priming with an epoxy
aluminium primer; (top right) after repair and with the two-pack, high solids, epoxy intermediate coat applied,
and (above) the final coat showing the subtle reflections of a mid-sheen topcoat (an aliphatic polyurethane)
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.
Application
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
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 recoatable aliphatic polyurethane
in graphite black with mid-sheen finish.
Colour and sheen
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
churchyard settings. 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.
Surface preparation
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