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To Scrape or Not to Scrape?

By Patrick Baty

The following article appeared in Traditional Paint News, Vol.1, No.2.

One really would have thought that in the treatment of historic houses the paint scrape had had its day. Yet only last week a book dealing with the restoration of Uppark has appeared, in which the making of scrapes "as pioneered by John Fowler" still seems to be regarded as a valid method of paint analysis.1

In spite of twenty-five years of articles and technical papers cautioning against the misuse of this technique, large numbers of intelligent people, some in positions of great responsibility, allow themselves to be fooled by its practitioners.2

If one were to suggest to a curator that he carry out the documentary research necessary for a particular project using just one book taken off the shelves of a provincial public library, one would be regarded as stupid, or, at best, mad. Yet the same curator will often be quite happy to employ an interior designer to scratch away at the paintwork with a scalpel, in the belief that this simple action will reveal the nature of an earlier painted colour scheme.

Admittedly, it is quite possible that the information contained in that one library book would broadly convey a certain amount of information that would be of use. However, with no corroborative evidence, and no use of primary source material, a very incomplete picture would inevitably be given.

A full technical analysis of the paint, on the other hand, might be compared to research in one of the major repositories of information, with access to original documents and the latest published works. Furthermore, the report that followed it would allow the investigative process itself to be examined, and supplementary research could be added to the work at later stages, the whole building up a fuller picture of the building concerned.

The reporting procedure following a scrape is, by definition, sketchy. If lucky, the appearance of a layer, and its apparent position in the stratigraphy will be explained. In the recent, and scandalous example of a major London house, however, colour boards of the layers relevant to the "restoration" were apparently all that were produced.

Analysis, on the other hand, consists of a number of different stages, and requires that the information obtained is tested at all stages of the procedure.

Let us understand that Paint Analysis will invariably consist of at least three processes, and will take place only after an examination of the documentary information available on the room/building.3

The sequence will be roughly as follows:

1) The taking of paint samples and the making of cross sections...these will then be drawn or photographed;

2) With the stratigraphy of the cross section made clear by a drawing, or photomicrograph, a scrape will then be made. The scrape must then be exposed to UV light for a period of time in order to clean up the colour.

3) Pigment and media identification will be carried out with the aid of a number of microscopical, and microchemical techniques.

4) The evaluation of the cleaned-up colour may be made by comparison with trial batches made up using the identified pigments.

The analyst will usually be accredited by a "competent authority", and will have a background in the study of early house-paint. The procedure will result in the submission of a written report with drawings, photographs, and technical data on the materials discovered.

There is no doubt that the analysis of a painted scheme is a lengthy procedure, but one that can do far more than reveal the colour of an earlier scheme. Indeed, very often an approximate date to each of the surviving layers can be given. As a result, the work of a particular architect / designer can sometimes be identified. Equally, if appropriate, the scheme that existed when the room was occupied by an historic figure can be established, and an accurate restoration to an earlier period attempted. The paint colour, in this case, being as important as the furnishings and the objects that the room once contained.

On the other hand, a Paint Scrape can be attempted by virtually anyone, and usually is, with a clutch of architectural historians, curators and interior decorators in the vanguard. There are no professional qualifications, nor courses run in this technique, and little opportunity for peer review.

There is no doubt that the action of scraping a painted surface will reveal some of the underlying layers. But apart from giving one a very rough idea of the colours used, and an approximate idea of the number of schemes, what else is revealed ?

Will a scrape identify the pigments used in a scheme, and therefore provide a clue to the date when it was applied ? Will it reveal the relationship of the scheme in one room with that in another ?4

Would a scrape have revealed that the scheme that survived in the Saloon at Uppark was the one applied by Humphry Repton in ca. 1815 ? Could I have known that the freshly revealed green scheme of a late seventeenth century gazebo was indeed blue if I had used my eyes and scalpel alone ?5

Why is it that the evidence of the scraper's handiwork is usually one of the first things to be painted out in any redecoration ? A recent visit to the Empress Josephine's house at Malmaison, has demonstrated very clearly the problems with leaving these tell-tale windows.

The Music Room6 retains several scrapes from the 1983 restoration. In each case the exposed first scheme is now significantly lighter than the surrounding "restored" paintwork Experience has shown, however, that when freshly exposed the original colour would have appeared much darker and more yellow than it does now. The reason for this phenomenon has been known in certain quarters for many years, but ignorance of this, or its rejection, has been responsible for the past often appearing murkier than was often the case.

In an attempt to measure the effect caused by years of exclusion from light by the application of later paints, a recent experiment was carried out by the author.

A 1930s edition of a Gliddens paint catalogue containing a large number of painted colour chips was examined. The colour names provided the first clue to the change that had taken place in many of the samples during the sixty years that the book had remained closed. "Sky Blue" had become a mid green, and "Cream White" a dirty putty colour, for example. The colours resembled those seen in freshly executed paint scrapes, and it was felt that the exclusion from light in this (closed) book had had a very similar effect to that of the overpainting of earlier paint on a wall.

Measurements were made of five colours with a spectrophotometer, and the paint samples were then left in an east-facing window under diffuse daylight. Repeat measurements were made every two or three days for the next four months, and the results recorded on a graph. The colours changed significantly during the period that they were exposed to light, with both the hue and the shade changing. The type of change that took place was similar in all colours, with the cleaned up examples being much lighter and much less yellow.7

In order to plot the changes that took place the colour difference DE*ab was recorded. These reveal an average DE of 9.92 units, with pale colours experiencing a DE of 14 units, and darker colours a DE of 6.63 units.8 For the first three months the rate of change continued at about a DE of .15 units each day.

When one considers that a colour difference, in a pale colour, of more than a DE of .50 units is clearly discernible, one will appreciate the problem.

The futility of relying on scrapes alone has been known for many years, yet still a number of people cling on to the nonsense. It appears that as well as being considered the easy option, this is a manifestation of the "shock of the new" phobia that afflicts a number of custodians; where technical analysis is automatically equated with brash new colours in faded surroundings, and where anything that smacks of science is, by definition, at variance with an aesthetically acceptable result.

The opening paragraph to this paper reveals, perhaps, a further reason behind the retention of scrapes in the curator's repertoire. It is not simply a question of "taste", it is, to a certain degree, snobbery. The late John Fowler is still often credited with having had the definitive approach to the treatment of historic interiors, and so methods practised by him thirty years ago are still advocated by his devotees and by aspiring "cognoscenti", eager to gain recognition.9

By listening to and understanding the importance of the following words of Gervase Jackson-Stops it will be seen that the paint scrape no longer has a place in the treatment of our cultural heritage:

Among the lessons learned from the tragedy of the Uppark fire has been the importance of recording not only the past history of the house but what we ourselves have done to it. We may make mistakes - in fact as humans we are bound to - but future generations are unlikely to blame us as long as we tell them what we did and why.

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1.Christopher Rowell and John Martin Robinson, Uppark Restored. London: The National Trust, 1996, 172.

2.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 1981 (vol. vi, 1982), 25-33.

3.The procedures of paint analysis have been discussed in greater depth elsewhere. See, for example: Patrick Baty, "The Role of Paint Analysis in the Historic Interior." The Journal of Architectural Conservation. March 1995: 27-37.

4.The very distinctive yellow pigment, orpiment, found in the second (salmon) scheme in the Large Library at Goodwood House, was also found in the first (green) scheme of the Tapestry Drawing Room. This information (together with other details) supported the belief that James Wyatt was responsible for both schemes, and gave weight to the theory that an earlier architect, possibly either Sir William Chambers or Matthew Brettingham, had originally designed the Large Library. (Patrick Baty, Goodwood House: A Report on the First Scheme, Following an Examination of the Painted Surfaces in the Large Library and in other Areas. 27th May 1996.)

5.See (Baty 1995, 33) for a full account. Briefly: what appeared to be green, having made a scrape, was revealed as being a discoloured Prussian blue scheme in cross section.

6.The Music Room at Malmaison is best known by the watercolour by Auguste Garnerey. This watercolour was begun in 1812 and finished by his sister in 1832. It appears as Fig. 157 on page 182 of Mario Praz's An Illustrated History of Interior Decoration, in the first paperback edition published by Thames and Hudson Ltd. London, 1994.

7.The lightest colours were nos. 1 (Cream White) and 2 (Light Buff). The darkest colour (Lemont Stone) was no. 3, and the two mid tone colours were no. 4 (Colonial Yellow) and no. 5 (Buff).

8.The CIE L*a*b* system of notation is the one most often used when measuring paint colour with a spectrophotometer. The L* indicates lightness, the a* and b* are the chromaticity coordinates, where +a* is the red direction, -a* is the green direction, +b* is the yellow direction.

9.It was refreshing to see signs of questioning taking place at Uppark, where, amongst other things, the 1970s pink (Fowler) scheme in the North Corridor was replaced with a stone colour, as used by Humphrey Repton in the early 19th century.

10.(Rowell and Robinson 1996, 178).

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