TO
STRIP OR NOT TO STRIP
– practical issues for historic paint
Preserving
multiple historic layers of paint for future generations as
gained importance as our knowledge and understanding of painted
surfaces has increased This then takes on a wider focus as part
of understanding the whole historic fabric.
However the conundrum that faces the property manager and the
painter is, retain the existing paint layers and risk an early
paint failure, or strip the paint back to the substrate to ensure
that a durable and protective paint system can be applied without
the uncertainty of failure.
When
considering paint programmes for historic buildings the experienced
building manager and either the Conservation Officer or English
Heritage will almost certainly request that samples are taken
before considering the application of any new paint.
What
will the paint sampling tell us? In its simplest form the analysis
should provide a time line of the paints used and their basic
constituents. This should be supplemented by dates against the
time line to indicate the last or first period of when a particular
paint was used and of course the colours. It can also give an
indication of the type of preparation that was carried out and
even a time lapse between applications. A competent paint annalist
will be able to provide a full list of ways in which the analysis
will inform the client of the history of the paint.
English Heritage has produced a publication
specifically related to paint analysis.
It
is widely recognised that, as each successive layer of paint
that is applied surface tension occurs as the paint dries. As
paint systems have developed through history, also surface tension
has increased particularly with modern treatments.
As layer upon layer is applied there will inevitably be a failure
or partial failure at some stage within the build up of paint
layers, usually at the weakest point between earlier layers.
This can often be attributed to poor application poor bonding
with the substrate or different paint mediums throughout the
many layers of paint. The signs are usually fairly evident,
paint cracked into cuboidal shapes and curling away from the
substrate, breaking down and peeling away from sharp corners,
excessive layers creating voids at internal corners.
These are the typical symptoms that experienced painters will
recognise as multiple layer failure.
Very
often details of past paint schemes have not been recorded and
it is not until the scaffold is erected and close inspection
reveals the presence of multiple historic paint layers. This
is the situation where it is initially apparent that the only
solution for achieving a durable paint system is to strip the
multiple layers away and start again. This then becomes the
difficult situation for all involved as the awareness of the
need to retain historic paint layers becomes apparent. This
situation is usually unwelcome, resulting in frustration and
delay, hasty and possibly irretrievable decisions and inevitable
increased costs.
Prior
investigation, recording and analysis, well ahead of the paint
programme will provide valuable information and avoid the unwanted
delays and escalating costs.
The investigation will provide valuable information that will
assist in the preparation of the specification. Decisions can
be made to employ specialists if required, paint mediums and
colours can be researched, and finally the difficult question
of strip or not to strip can be taken.
Where
the historic paint is particularly sensitive and needs to be
retained but it is in a poor condition decisions and compromise
has to be reached. Nothing related to the preservation of historic
buildings is black and white (apologies for the pun) where a
set of guidelines can apply to every situation. Each situation
must be considered on its own merits.
How is the solution of ‘stripping or not stripping’
resolved to the satisfaction of the building manager who requires
a durable paint system and over painting historic layers that
may result in a premature failure of a paint system?
There
are specialists who are able to carefully remove and peel away
the layers revealing a sound surface somewhere in the middle
of the multiple layers. This maybe considered a sound approach
for smaller specific items of historic significance. The reality
is that, this is not a practical or economic solution where
large areas of historic buildings are to be painted.
The
information gathered during a preliminary investigation will
need to contain detailed photography, historical background
and past paint records if available.
Paint analysis taken over a number of areas will produce a comprehensive
picture of the paint history.
Paint programmes do not always follow a logical sequence and
different schemes may have been applied at different times to
different areas.
Having gathered this information the choice of colours maybe
influenced by the results of the analysis and also the choice
of materials. It may alter the initial decision to strip or
not to strip away the historic layers of paint.
The investigation may influence the choice of paint medium,
possibly the use of lead paint maybe considered after considering
the health and safety implications.
Tension free paints could be considered if it was felt that
the historic layers could withstand repeated application without
premature failure. These decisions however have to set in the
context of the building and its use.
As
we have said nothing is black or white in making decisions with
the painting of historic buildings. There maybe situations where
the full sequence of layers is firmly adhered to the substrate
and no indication of failure but patches within the same paint
system have failed, possibly revealing the substrate. This is
a situation where it would be possible to retain the remaining
build up of historic layers.
The difficulty occurs at the distinct change in levels between
the new and existing that would be deemed to be unsightly. As
custodians of historic buildings we have to balance the issues
of accepting and recognising past treatments. In this case,
it would be pragmatic to record the areas of sound paint and
accept that there will be changes in levels between old and
new paint.
We also know the folly and failure of the excessive use of fillers
to level out the surface. Prudent use of abrasives to feather
out the edges and a minimal use of fillers will lessen the effect
o
f the abrupt step but record what was undertaken and why.
When it is apparent that the whole system has failed and the
substrate is suffering as a result, there is no real alternative
to stripping away the existing system. In this situation where
it is important to retain some evidence it maybe appropriate
to select and carefully record an area where original layers
can be retained.
New paint is applied knowing that early failures can be anticipated
and revisiting the site on a regular basis is built into the
routine management.
In choosing an area to retain the historic record it maybe prudent
to employ a specialist to undertake the preservation.
These
issues maybe common sense to many working in the field of paint
treatments to historic buildings but there are many recorded
incidences of where valuable evidence has been stripped away
without a thought of what the paint can tell us about the building
and how it may inform future generations. Prior investigation
will inform and prevent some of the tragedies of the past.
Richard
Roberts
THE TRADITIONAL PAINT FORUM
C/o Hon.Secretary: Una Richards, The National Trust for Scotland,
28 Charlotte Square, Edinburgh EH2 4ET
Please
Note: SMUDGE is a regular news and information supplement to
the annual journal TRADITONAL PAINT NEWS. Each issue of SMUDGE
is written, in turn, by a member of The Traditional Paint Forum,
subject tothe control of the Committee. The information is provided
in good faith. It is not necessarily the view of other members
of the Forum; it is offered only as a contribution to the ongoing
debate.
