The Repair of Wrought and Cast Iron Work - Dublin City Council
The Repair of Wrought and Cast Iron Work - Dublin City Council
The Repair of Wrought and Cast Iron Work - Dublin City Council
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IRON THE REPAIR OF WROUGHT AND CAST IRONWORK<br />
<strong>The</strong> surface should be thoroughly cleaned before fresh<br />
paint is applied. Any areas <strong>of</strong> corrosion should be<br />
removed completely by chipping rust away <strong>and</strong> using<br />
a wire brush <strong>and</strong> s<strong>and</strong>paper to clean the surface<br />
thoroughly to prevent it spoiling the new coat <strong>of</strong><br />
paint. Areas <strong>of</strong> sound paint can be cleaned by washing<br />
with water, or by wiping down with white spirits <strong>and</strong><br />
allowing them to dry thoroughly. Next, existing paint<br />
should be s<strong>and</strong>ed lightly to form a good key for the<br />
next layer <strong>of</strong> paint. Any areas <strong>of</strong> damaged paint that<br />
need to be patched should be s<strong>and</strong>ed back to a<br />
smooth edge before new paint is applied. New paint<br />
should overlap the existing by about 50mm.<br />
CHOOSING THE RIGHT PAINT SYSTEM<br />
When it comes to re-painting traditional ironwork,<br />
there are generally two options: either a traditional<br />
paint system or a modern one can be used. If historic<br />
<strong>and</strong> aesthetic authenticity is important, traditional<br />
paint may be the preferred choice. A new coating<br />
should aim to match the original (if this can be<br />
identified) not only in colour but also in surface<br />
texture, composition, <strong>and</strong> sheen level. Even if the<br />
composition <strong>of</strong> the original historic paint cannot be<br />
matched, for example if permission cannot be<br />
obtained to use lead-based paint, it should still be<br />
possible to match the texture <strong>and</strong> colour <strong>of</strong> the<br />
original scheme. Modern paint production allows<br />
colours to be matched very closely to those derived<br />
from paint samples.<br />
Traditional paints have proven their effectiveness <strong>and</strong><br />
durability over centuries <strong>of</strong> wear. Red lead paint was<br />
one <strong>of</strong> the most common forms <strong>of</strong> primer for iron, <strong>and</strong><br />
was usually painted over with oil-based (usually<br />
linseed) paints containing lead. Bitumen <strong>and</strong> pitch<br />
were used over a primer to coat corrugated iron.<br />
Corrugated iron was commonly galvanized from the<br />
end <strong>of</strong> the nineteenth century. Nowadays the use <strong>of</strong><br />
lead-based paints is controlled due to their toxicity.<br />
<strong>The</strong>ir use can be licensed by the Health & Safety<br />
Authority for use on certain types <strong>of</strong> historic buildings.<br />
However, red lead paint is still widely available<br />
(particularly from ch<strong>and</strong>lers). <strong>The</strong>re are no restrictions<br />
on its use as a paint because it is less toxic than paint<br />
containing white lead.<br />
Traditional paints can be highly effective. However,<br />
when deciding to use such paints, it is important to<br />
consider future painting; how likely are future owners<br />
or caretakers <strong>of</strong> the ironwork to use traditional paints<br />
Will the paint system be compatible with modern<br />
paints if these are applied in the future <strong>The</strong> best<br />
approach to be taken should be decided on a case-bycase<br />
basis, as factors such as the historical significance<br />
<strong>of</strong> the ironwork, budget available, <strong>and</strong> required<br />
performance will vary from project to project. For<br />
some projects, a modern paint system may be more<br />
suitable. <strong>The</strong>re are many types <strong>of</strong> modern coating<br />
systems on the market, many <strong>of</strong> which are highly<br />
effective. Paint manufacturers will normally guarantee<br />
their systems for a set number <strong>of</strong> years although such<br />
guarantees do not negate the need for regular<br />
inspections <strong>and</strong> maintenance, <strong>and</strong> ironwork should<br />
always be inspected long before the given number <strong>of</strong><br />
years to first maintenance.<br />
BEST PRACTICE FOR PAINTING BARE METAL<br />
Current best practice recommends the following system:<br />
> Two coats <strong>of</strong> a zinc-based primer<br />
> One or two base coats <strong>of</strong> micaceous iron oxide<br />
(MIO)<br />
> One or two top coats <strong>of</strong> gloss paint<br />
A dry film thickness (DFT) <strong>of</strong> no more than about 250<br />
microns is generally recommended. This is the<br />
thickness to which the layers <strong>of</strong> paint dry. DFT<br />
measures can be bought from many hardware stores.<br />
Hard-shell epoxy paints are not recommended as<br />
these are not flexible enough to allow for the natural<br />
thermal expansion <strong>and</strong> contraction <strong>of</strong> iron.<br />
CHOOSING A COLOUR SCHEME<br />
Where a historic colour scheme can be identified<br />
through the analysis <strong>of</strong> paint samples, it may be<br />
desirable to reinstate the earlier or original paint<br />
scheme. However, changes in colour may require<br />
planning permission so it is advisable to consult the<br />
relevant local authority before undertaking repainting.<br />
Gilding was sometimes applied to highlight certain<br />
features <strong>of</strong> the ironwork. Gold paint is a frequent<br />
substitute for gold leaf but tends to weather to a dull<br />
<strong>and</strong> unattractive brown. Gilding is not overly<br />
expensive or complicated to do, <strong>and</strong> provides far<br />
better long-term results. However, gilding may not be<br />
appropriate in some circumstances – for instance,<br />
railings around a terraced property where<br />
neighbouring properties do not have gilded ironwork.<br />
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