Spectral properties of the Shroud of Turin

Spectrophotometric results from the 1978 investigation of the Shroud of Turin are presented. The goals of the investigation were to characterize spectrally the body image in a region extending from the near UV to the near IR, to determine if the blood stains are actually blood, and to recommend storage parameters to prevent further degradation of the image. The bloodstained areas have the spectral characteristics of human hemoglobin. The image shows monotonically increasing (featureless) absorption with decreasing wavelength. The contrast is low: R(550 nm) = 0.85 of that for the background linen. Simulated aging by air baking reproduced the color of the background linen. Simultaneously, an invisible deposit of perspiration plus skin oils became visible and displayed a reflection spectrum closely resembling that of the body image. Lightly scorched areas on the Shroud are also somewhat similar spectrally, suggesting that a similar resultant chemistry is possible for dissimilar causes. A likely cause for the bo y image is cellulose degradation stimulated locally by natural or applied substances transferred to the Shroud.