Low cost radiographic techniques in art anaylsis
Radiography has become an important tool in art restoration today. Without it, many of the great discoveries of recent years would not have been possible. Its high cost, however, has become a serious obstacle for the small museums and galleries around the country. It is not unusual for a single x-ray study of a painting to cost over a hundred dollars. In a time of decreasing government funding, a low cost alternative to traditional x-ray techniques would prove valuable. It is the purpose of this paper to explore just such a technique.X-rays are effective in studying paintings because the pigments used in forming the paints vary greatly in composition and density. Since x-rays are absorbed differentially depending on the density of the absorbing material, older paints, which tend to be much denser due to a high lead content, are good absorbers and produce dark shadows on x-ray film. More recent paints, being significantly less dense,are poor absorbers and do not produce such dark shadows. Thus, it is possible to discern the shadows of underlying paintings on x-ray film enabling trained persons to make a judgement on the advisability of treating a painting to restore it to its original state.X-rays show stretch marks in the canvas which can help determine the age of a painting. Repairs to the painting also show up well in x-rays. It is evident that cracks and holes in a picture allow the x-rays to penetrate more easily and allow more exposure of the film than do the complete parts of the picture. When these holes are filled and covered, the x-ray still may record them, since it is practically impossible for a restorer to replace the exact amount of exactly the right density of material and to make the junction between old and new a perfect blending of materials [Burroughs, p. 54]. It is also possible to tell from brush strokes if two artists worked on the painting since, like different handwritings in a corrected manuscript, we may be able to distinguish between them, even though only one is visible on the surface of the work [Burroughs, p. 52].Low energy gamma radiation is physically identical to x-radiation. Low level radioactive sources may thus be substituted for more expensive, high intensity x-ray generators. Using low level radioactive sources provides portability, low cost, and minimal health hazards. This method will have a projected cost on the order of $2 or $3 per x-ray after the initial cost of purchasing a source. Sources cost from $200 to $1000 depending on radioactive isotope activity. The initial cost will be recouped after only a few x-rays have been taken. Even if the recorded x-rays are not of the best quality, they may help the curator decide which paintings to have professionally examined, thus saving limited restoration dollars.