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.

 
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