By Patrick Baty

We can all perhaps relate to this frustration, this inability of the human language to accurately convey a colour. Apart from black and white, there was a time when words alone could only vaguely point one in the general direction of what colour was wanted.

For the owner of an historic house, this had not presented a major problem. He had either left the existing scheme untouched, or had relied on the skills of a traditional craftsman to mix the required shade.

However, by now, it could be that the existing scheme is so worn that it threatens to give the wrong message to visitors, and positively discourage corporate clients. Similarly, the skills of the house-painter no longer seem to match those of his father's generation.(2)

In recent years the appearance of paint ranges with seemingly countless colours has not provided the answer. How often has the painter's version of Lily White matched that on your colour card - indeed, is that colour still available? Have you always managed to find exactly the colour you wanted amongst the many thousands on offer? Conversely, you might have already given up that option and settled on a smaller range. However, do you really want the bland uniformity that results from choosing from the same 57 varieties employed in many of the houses run by our largest heritage organisation?

Aim

The purpose of this article is to show how recent technical advances can eliminate much of the frustration and expense that paint colour so often seems to lead to.

The Portable Spectrophotometer

Since 1995 we have been using a portable spectrophotometer to supplement our forty years' experience of matching paint colour. Although those human skills are still essential, technology has allowed us to do things never before possible. As a means of improving accuracy and speed, eliminating doubt, and reducing cost, the spectrophotometer has paid for itself several times over.

So what! How can this development be of any concern to the owner of an historic house? A brief description of what it is, and how we have been using it might suggest a few relevant applications.

The portable spectrophotometer is a hand-held instrument that can measure paint colour, and allow its accurate reproduction. A customer can either bring in, or send, a colour to be matched. The sample can be in the form of a paint flake, a piece of wallpaper, or fabric, a lump of stone or brick, or one of the many countless objects that we have been faced with to date. We also have an extensive range of colour references, and paint colour cards (English and foreign) - some dating back to 1807. So if a Pea Green from the 1846 edition of D.R. Hay's Nomenclature of Colours, or an Imperial Chinese Yellow from the 1952 edition of Thomas Parsons' Historical Coloursis required, let us know and we can produce it. Similarly, the colour on a piece of wall plaster brought back by Sir John Soane from Herculaneum is one of a number of the more esoteric colours on file.

Culzean Castle, Ayrshire -  The "perfect" cross section - paint from a door in the Walled Garden.

Frequently, however, the colour is on an object that cannot be moved, and we are asked to measure colours in situ. It may be that an area of localised damage needs to be painted to match the colour on the surrounding wall. Perhaps the room is too large, and time and money too limited to permit a complete repaint. The paint could be from a discontinued or unknown source. Cost-effective inpainting is made possible by measuring the paint, and producing a new tin that matches the original under all lighting conditions.

Metamerism

Traditionally, colour matching has resulted in what is known as a metameric match - an apparent colour variation that becomes clear in different light conditions (especially beside a window, or in photographs if a flash is used). For years the big retailers have been using spectrophotometry to combat metamerism. In this way they can ensure that the coat and trousers of a ready-made suit, which might have been manufactured on different continents, actually match when the customer steps out of the shop.

Computer software with the spectrophotometer allows colour matches to be made for all light conditions (daylight, domestic lighting and office lighting being the most commonly specified) and metamerism can be avoided, or predicted, if inevitable.

Colour Surveys

We are often asked to make a site visit in order to carry out a full colour survey. Even the best run establishments lose track of what colours have been used, but either see no reason to change the existing scheme of decoration, or want to rationalise it. Umpteen variations of off-white were identified at Lancaster House, for example, and it was decided that this was causing too much confusion for the maintenance programme. After an hour-long survey, each colour was identified, and a proposal made for the gradual reintroduction of a single colour.

On-site colour surveys have been carried out for various reasons elsewhere. At Spencer House, and No 1 Greek Street, the colours produced as part of recent restoration projects were measured in order to facilitate redecoration. In both instances, the paint had originally been mixed up in buckets under the supervision of consultants. Needless to say, as a result, identification and formulation of a paint colour, minimising delays and costs.

In an attempt to give greater articulation to the architecture, John Fowler had introduced a number of colours in the Entrance Hall at Syon House. Twenty–five years later possible options for redecoration were being considered. One school of thought felt that there was no reason to change the Fowler scheme. Once again, a survey has identified these colours and a seamless redecoration, using the same colours, can now be carried out if required.

Occasionally, there is no wish to carry out redecoration, and a survey is requested as part of a condition report. This sort of work was undertaken at Newhailes, in East Lothian, for example. Although there was no intention to overpaint large areas of surviving eighteenth and nineteenth century paint, it was thought important to record how the rooms looked.

We do a lot of work in clubland, in institutions where the fine line between minimum change and good maintenance tends to be observed. In one club, members had grown used to the nicotine-stained ceiling of the Cocktail Bar. The Secretary, however, wanted to tidy up the room without upsetting any sensibilities. Colour measurements were taken, and paint produced to match the average of the stained ceiling.

In view of the speed and comparative ease with which a colour survey can be completed, once on site, it is usual for us to be asked to take measurements from the whole building. These can be stored indefinitely on computer, and brought out when needed.

Spectrophotometry can also be used for camouflage purposes, and colour matches made to many natural finishes. By taking several measurements of a Portland stone façade, for example, the average colour can be found and produced in the form of a masonry paint for the render of a new extension, or in an oil paint for gutters and downpipes.

Paint Analysis

Increasingly, especially in houses open to the public, efforts are being taken to establish how a room had been decorated at an earlier stage. Experience has shown that the paint scrapes much used by an earlier generation of interior decorators provide no meaningful information.(3)

However, the analysis of decorative schemes by examining cross-sections taken from a room is well established, and many recent restoration projects have employed this technique.(4)

For a client commissioning paint analysis it is important that the investment is safeguarded by maintaining quality control throughout all phases of the project. Using the spectrophotometer, paints can be mixed to match the colour samples provided in the report, and the colour of the earlier scheme reproduced exactly.

Restoration projects often come adrift when the contractor is handed a copy of a paint report. Unless he employs craftsmen who can mix colours on site, he will have to try and find the closest paint colour on his colour card. Invariably, no lighting conditions are stipulated and the impression given is that if a match is close, it will do. Either way, problems will result. In the one instance, a good but metameric match will be produced - one that will prove hard to re-match when maintenance painting is required. In the other, a colour only partially resembling the earlier one is applied. One might ask why the analysis has been commissioned if the findings are not to be acted on.

In the same way that the architect will check that the leadwork meets his specification by examining it, for example, it is now possible for him to ensure that the stipulated paint colours are applied. As a result the specifier, the contractor, and the client are all protected from the strained conversations and accusations that sometimes result.

Some years ago, having carried out analysis on the external windows of a major London site, I was summoned by an irate client, and his contractor, to explain why the colour being applied to the external windows looked positively "mustard", instead of the expected off-white. By taking measurements of the paint that had been ordered, and comparing it with the sample in my report, it was quite clear where the problem lay. The contractor had asked a paint manufacturer to match the sample, but had not thought fit to check the results before putting it on. This led to delays to the project, extra expense, wasted paint, and a certain amount of exasperation all round. If a sample of the "matched" paint had been submitted for spectrophotometric measurement beforehand, none of this need have happened.

The Gloss Meter

The reproduction of the colour is just one factor to consider. No one would suggest that a modern alkyd oil paint could ever entirely match the appearance of an early lead-based paint. Such a paint had a texture and level of sheen not readily available today. However, once again, technology can provide some help in the form of an instrument that measures how shiny a surface is. In tandem with the spectrophotometer, we have also been using a Gloss Meter to record the appearance of a surface. Supplied with both the colour data, and gloss level, a competent paint manufacturer could produce a closer match to the original.

The Future?

Yet further developments are happening all the time. On a recent project, we were asked to visit a Soane house of 1793 and make suggestions for the redecoration of four areas, using colours that were typical of the period. Rather unusually, we were requested to include full colorimetric data for the colours that were being suggested. This was in addition to the more usual provision of painted samples, and the citation of relevant precedent. The client's architect was able to apply the colours to digital photographs on his computer screen. The coloured images could then be printed out for assessment, without even putting a brush to the wall. In this instance, being a semi-public building, with a busy programme of functions, speed and minimum disruption were vital.

From being an instrument that was once the size of a small car, and one restricted to very limited scientific procedures, the portable spectrophotometer can be employed almost anywhere. Combined with a knowledge of early painting practices, and the skills of a colour-matcher, it now has a special application in the historic house.

NOTES

1.Robert Louis Stevenson, Valima Letters. New York, Scribner's, 1901: 194.

2.Please note, the author is not suggesting that redecoration is always the best option. He has been a fully paid up member of the Leave it Alone Society for a number of years.

3.The argument against scrapes has been well rehearsed. See the following:

Morgan Phillips and Christopher Whitney, "The Restoration of Original Paints at Otis House," Old Time New England. Boston, Mass.: The Society for the Preservation of New England Antiquities, vol LXII, no 1, (Summer 1971): 25-28.Morgan Phillips, "Problems in the Restoration and Preservation of Old House Paints," in Preservation and Conservation, Principles and Practices. Washington, D.C.: The Preservation Press, 1972: 273-285.

Ian C. Bristow, "Repainting Eighteenth-Century Interiors," ASCHB Transactions vol vi 1982 (1981): 25-33.

Patrick Baty, "The Role of Paint Analysis in the Historic Interior," The Journal of Architectural Conservation (March 1995): 27-37.

Patrick Baty, "To Scrape or Not," Traditional Paint News vol 1, no 2 (October 1996): 9-15.

Patrick Baty, "The Benefit of Hindsight: Some Tips on Commissioning Paint Analysis." An article in the course of publication. It follows the English Heritage Layers of Understanding conference that took place in London, on 28th April 2000.

No literature outlining the benefits of scrapes is known, though, incredibly, the practice is still very much alive in many quarters.

4.A number of the better-known projects include: Uppark, Windsor Castle, Hampton Court Palace, and Temple Newsam. For an account of the process see Patrick Baty, "The Role of Paint Analysis in the Historic Interior." The Journal of Architectural Conservation. March 1995: 27-37.

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Patrick, is a specialist in the use of paint and colour in historic buildings with many years experience. Following a research degree in the subject he has consulted on countless restoration projects. Buildings range from Royal palaces; country houses and cathedrals to museums; a wartime RAF station and London housing estates. Royal Festival Hall.

He has been a Trustee of the Georgian Group for 20 years and a Fellow of both the Society of Antiquaries of Scotland and the Royal Society for the encouragement of Arts, Manufactures & Commerce. He is a founding member of both the Architectural Paint Group and the Traditional Paint Forum. In 2007 his company was granted a Royal Warrant of Appointment to Her Majesty The Queen for his work on colour.

Patrick has pioneered the use of spectrophotometry in historic buildings and is frequently employed to make colour surveys.

 

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