Carbon-14 Dating of the Holy Shroud in 1988
Q. In 1988 small samples cut from one corner of the Shroud were radiocarbon dated and declared to be of mediaeval origin (‘radiocarbon age’ 691 years ± 31; Historical age between 1262 and 1384 A.D. at 95% confidence). Why do Shroud scientists in the main now view this declaration as erroneous?
Q. What is radiocarbon dating?
Q. How does contamination of the Holy Shroud test samples affect the radiocarbon results?
Q. What is the date of origin for the Shroud?
· The 1989 assertion of a mediaeval age for the Shroud of around 1300 A.D. is erroneous because the analysis failed to take into account the 87% initial, and the 50% final, non-removable contamination of the test samples, which had been cut from a heavily handled corner of the Shroud.
· Corrections for the contamination point to an ancient origin for the Shroud in the 3rd to 4th century or earlier.
· Corrections for a possible neutron flux could further push the age back towards the 1st century A.D.
· Carbon -14 dating results now agree with the evidence from other scientific and scholarly research that that the Shroud is ancient and not mediaeval.
1. Radiocarbon Dating: What is it?
Carbon-14, also called radiocarbon or radioactive carbon (14C, C14 ) exists in very small traces in the atmosphere. It originates in the upper atmosphere, formed by the interaction of cosmic radiation with atmospheric nitrogen, and then it diffuses gradually down to the earth’s surface. It is absorbed from the air by all living organisms during respiration so long as the organism lives. At the moment the organism dies the amount of carbon-14, and its ratio to ordinary non-decaying, non-radioactive organic carbon, is fixed. Moreover, the decay rate of carbon-14 is known very precisely. Therefore if the carbon-14 amount remaining in a sample is measured a number of years after the organism died, this can tell us when the organism lived. Thus, linen cloth can be dated to the time the flax plants from which the linen was made were harvested.
If we represent the number of C14 atoms at any given time after the death of the organism by N, and original number of C14 atoms at the time of origin of the sample by No, then the decay rate is given mathematically as
N/No = e-kt
where t is time elapsed between origin and sampling in years, k is the decay constant, which for carbon-14 has the value 0.0001209, and e is the number 2.71828, the base of natural logarithms. This mathematical relationship, its graph and it application are discussed in some detail in the link Carbon 14 dating calculations.)
How carbon dating is done can be seen from some simple examples. First let us suppose we have a clean linen cloth that we are sure on other grounds originated from the 1st century A.D., for example from the year 1 A.D. Let us then cut a small sample from this linen cloth (say, weight 10 milligram and area of sample 1 square centimeter) and run a dating test on it in the year 2000. Then the calculations show that we should expect to get a ‘radiocarbon age’ of 1999 years. This corresponds to an historical date of origin of 1 A.D (. since 2000 – 1999 = 1 ) So, in the case of a clean test sample, the procedure is relatively straightforward.
Second, let us take the same sample ( weight 10 milligrams), but this time we suppose that, just as the technician is about to test it, he inadvertently drops it into olive oil so that it becomes contaminated with 10 milligrams of olive oil. The contaminated sample now weighs a total of 20 milligrams, half of its new weight being 10 milligrams of clean linen and half being 10 milligrams of contaminating olive oil. Then, let us further suppose that, to avoid exposing the clumsiness to colleagues, the technician doesn’t try to clean the olive oil off, but just goes ahead with the radiocarbon tests on the contaminated sample. What ‘radiocarbon age’ will we then get from the instrument? Well, since the weight of sample and contaminating olive are equal, it is obviously going to come out somewhere about halfway between 1 A.D,. the date of origin of the cloth and 2000 A.D. the date of origin of the olive oil. In fact, the ‘radiocarbon elapsed time age t’ turns out to be 945 years, so that the historical origin of the cloth appears to be 1055 A.D ( 2000 – 945 = 1055 A.D.) in spite of the fact that we know that the true age of the clean cloth itself is 1 A.D. (See Carbon 14 dating calculations )
Finally, suppose the 10 milligrams of contaminating olive oil had been added a little bit each year from 1 A.D. to 2000 A,D, the year of our hypothetical test, and that the oil had become bonded to the linen so strongly that it was non-removable by cleaning. What radiocarbon test age t would we get now? Well, the Carbon 14 in the oil gradually added over the 20 centuries would itself decay radioactively so that the average age of the contaminating olive oil would now be about 1000 A.D, which is the mid- point over the linen cloth’s history from 1 A.D. to our hypothetical test year of 2000 A.D. . In this case the calculations give us a ‘radiocarbon age’ t for the linen plus the accumulated olive oil of 1487 years. The apparent historical age of the cloth would then be 2000 -1487 = 513 A.D., so that the effect of adding non-removable contamination, either all at once or a little bit at a time, is to advance the apparent age of the cloth from its true age. We now turn to the Shroud of Turin.
The Holy Shroud of Turin dating test in 1988 on contaminated samples
While a 1st century origin of the Shroud of Turin is today accepted by a majority of those people studying it, still, for some there may remain an apparent obstacle to accepting its authenticity because of a 1989 Report in Nature ( Damon et al. ) on the carbon-14 testing of three tiny samples from the Shroud, which Report asserted that the linen was of mediaeval origin. What is not widely realized yet, however, is that the 1989 carbon-14 test result, properly calculated, actually points to an ancient origin for the Shroud, and it is a mediaeval origin that is ruled out
Here is what happened. Three postage stamp size samples were cut from a heavily-handled corner of the Shroud and dated by radiocarbon analysis to yield an average radiocarbon age of 691 years BP ( Before Present ), which was then interpreted by the authors of a report in Nature  in 1989 to mean a mediaeval historical date for the origin of the linen of around 1297 A.D. ( 1988-691 = 1297). Since the overwhelming conclusion from all other scholarly and scientific research was in favor of the traditional first century origin for the Shroud around 33 A.D., this anomalous radiocarbon date was subject to intense examination and criticism
Naturally, any contamination of a linen test sample, for example, by organic material containing animal or plant carbon, will distort the Carbon-14 measurements by adding Carbon-14 of a different age from the original sample, and this will confuse the dating. Any contamination, therefore, must either (1) be removed by cleaning the sample, or, (2) if it is non-removable, then its presence must be quantitatively corrected for in the numerical interpretation of the results of the radiocarbon counting.
First, as to the organic carbon contamination of the test samples; they were cut from a heavily handled corner of the Shroud, and were known to be heavily contaminated, since their unit area weight, or specific weight, was 42.9 mg/sq. cm. ( 50 mg /1.166 sq. cm area = 42.9 mg/sq. cm.) But, since the average specific weight for the Shroud as a whole is known to be only 23 mg/sq.cm. then the contamination ratio is 42.9/23 = 1.87 ( i.e. 87% contamination). ( See Carbon 14 dating calculations). None of this was mentioned in the Nature report which properly gave the weights of the three samples, but, astonishingly, the authors omitted to give the size of the samples so that the unit area weight was not made available. For some time following this unprecedented breach of scientific practice, other researchers were forced to simply speculate on the facts as to the sample sizes. The official Turin data, now available, are given as follows
Fig. 1. Official Turin data on the 1988 sampling procedure
The 7 x 1 cm trimmed strip was first cut in half, and then three equal samples were cut from this one-half piece. This makes each of the three samples 1/3 of 3.5 sq. cm or 1.166 sq. cm. in area ( i.e. “ a little more than a square centimeter” as stated by Gino Moretto, former Secretary to the International Centre of Sindonology of Turin and Secretary of the Journal Sindon, in his admirable book The Shroud: A Guide .
The unit area weight of each sample is then calculated as the weight, 50 milligrams, divided by the area of 1.166 sq.cm, which gives us 42.9 mg. per sq. cm. ( 50/1.166 = 42.9). Since the average unit area weight for the Shroud linen as a whole, away from any heavily handled corner, is known to be only 23 mg per sq. cm, we have a ratio of contamination 42.9/23 or 1.87 i.e. 87%. This is not at all surprising since the samples were cut from a corner heavily handled over centuries, and this is so marked that it shows up as a darker area in all the photographs of the Shroud.
To study this, experiments have been made to determine the amount of extra weight that is taken up from human fingerprint contamination in handling an object, The weight of skin oils from fingerprints on glass microscope slides was found to be from 10-5 to 10-3 grams per print. Even 10-5 grams of oily contamination per human fingerprint would readily account for the 87 % contamination amounts found at the heavily handled corner of the Shroud from which the 1988 test samples were cut (Power ).
Calculation of the historical date of origin of the Holy Shroud
If this 87% contamination is removable by cleaning, then there is no adjustment needed to the radiocarbon date and the approximate historical age is just 1988-691 = 1297 A.D. ( within statistical errors). But the Nature authors specifically stated that they did clean the samples, and, in the case of the sample tested at Zurich, they said that that there was “no evidence of contamination” after the attempted cleaning. This would mean that the 87% contamination was non-removable, and so their instrumental radiocarbon age had to be adjusted, but this was not done .
However, the late Prof. E.T. Hall of the Oxford radiocarbon team and himself one of the Nature authors, added later that there was a loss on cleaning which averaged about 20% . Leaving aside the problem of the contradiction in this ‘off the record’, unofficial, belated admission of contamination, let us take Prof. Hall’s figure at face value and reduce the contamination ratio by his 20% from 1.87 to 1.50 ( 0.8 x 1.87 = 1.496) so that we are left with at least a 50% net, non-removable contamination of the three samples.
We can now make the necessary correction to the 691 ‘radiocarbon age’ by estimating the age of origin of the 50 % carbon contamination. The details and calculations are given in (See Carbon 14 dating calculations). The conclusions are that the radiocarbon age t, corrected for the non-removable contamination of 50%, should be 1631 B.P., and that therefore the approximate historical age for the Shroud on this corrected estimate is around 357 A.D. ( 1988-1631 = 357). Other reasonable estimates for the age of the non-removable contamination give somewhat earlier or somewhat later estimates for the Shroud’s date of origin , but all of them refute the mediaeval claim by many centuries There is also, of course, a confidence spread on the 357 A.D. statistical estimate. The 95% confidence values of the Nature study were about ± 90 years, although there was such a variability among the samples that the limits are disputed. However, using them as given, we get 357 ± 90 = 447 to 267 A.D.. The conclusion is that the radiocarbon test shows that the Shroud is ancient and not mediaeval.
Finally we must ask the question: Has there been any enrichment of the C14 content since the flax was harvested in addition to the contamination from human handling of the corner of the cloth, for example by a neutron flux as discussed in 1988 by Phillips and Hedges , and subsequently investigated experimentally by Rinaudo ? If so, then we must adjust the radiocarbon age for it. Such proton enrichment could further reduce the age of origin from 357 A.D. back towards a first century date.
· The 1988 assertion of a mediaeval age for the Shroud of around 1300 A.D. is erroneous, because the analysis failed to take into account the 87% initial, and the 50% final, non-removable contamination of the test samples, which had been cut from a heavily handled corner of the Shroud.
· Corrections for the contamination point to an ancient origin in the 3rd to 5th century or earlier (357 ± 90 = 447 to 267 A.D.).
· Corrections for a possible neutron flux could further add to the historical age of the Shroud
· Carbon -14 dating results now agree with the evidence from other scientific and scholarly research that that the Shroud is ancient and not mediaeval.
References and Notes
1. P.E. Damon, et al., “Radiocarbon dating of the Shroud of Turin”, Nature, 337, 6208, pp 611-615, Sept. 11, 1989.
2. It is customary in radiocarbon work to take B.P. ( “before present” ) to mean “before 1950 A.D.” . This small technical correction to the calculation of dates is ignored here for reasons of clarity. It would mean an adjustment to calculated dates of only 38 years ( 1988-1950 = 38).
3. Gino Moretto, The Shroud: A Guide ( English transl.). Paulist Press, New York, N.Y. 1996.
4. Bernard A. Power, Datazione con il 14C ed Energia d’Immagine per la Sindone di Torino. Collegamento pro Sindone, Roma, Settembre-Ottobre, pp 20-34, 1992.
5. T.J. Phillips and R.E.M. Hedges. Correspondence in Nature, 337, 16 February, p. 594. 1989.
--------- T.J. Phillips, Reply to Dr. R.E.M Hedges’ Nature correspondence . British Society for the Shroud of Turin Newsletter No. 22, May 1989, pp. 8-11
6. J. B. Rinaudo, “Image formation on the Shroud of Turin explained by a protonic model affecting radiocarbon dating” III Congresso internazionale di studi sulla Sindone, Torino, 5-7 Giugno 1998.
---------------------, “Theory No. 3: French Scientist Jean-Baptiste Rinaudo”. British Society for the Shroud of Turin Newsletter. No. 38, Aug.-Sept., 1994.
7. The Report in Nature: Since 1989 there has been a vigorous study and debate among Shroud scientists and scholars on this report. The Nature authors, in an extraordinary breach of usual scientific practice, have refused to enter any debate or to release any of their data . The history of this affair can be reviewed at various websites (Links to other websites). However, the mass-media have in the main continued to present the mediaeval radiocarbon claim in Nature as definitive, and as preempting all other scientific and scholarly conclusions of the past hundred years.
We should add here that problems with contamination are routine in radiocarbon dating. It is not uncommon for an ancient artifact, known by other reasons to date from a certain era, to give a radiocarbon date completely at variance with the known facts. In these cases the researcher ordinarily just shrugs off the result as an unfortunate technical problem with contamination that cannot at present be coped with, or he adjusts the historical age calculations accordingly and gets on with the research.
However, it appears that because we are here dealing with the Holy Shroud of Turin, with its enormous theological, philosophical, historical and international implications, the supposed controversy over the carbon 14 dating result is artificially being kept alive for polemical reasons, and the pretense is that there still is a valid controversy as to the authenticity and age of the Shroud. It is all a sham, and is moreover a serious impediment to on-going scientific work. The current consensus and conclusion is that the Shroud’s age is ancient. The claim of a mediaeval historical date is today purely fictional.
8. Correction for Carbon 14 enhancement by neutron flux, if any: The exchange between Phillips and Hedges  on this matter in Nature in 1989  generated widespread interest and discussion. One objection raised to the C14 enhancement by neutron flow was that, while neutrons would undoubtedly enrich the C14 content of linen, there was no proof that the new C14 atoms so produced would remain in the linen and not just simply diffuse out and evaporate into the air.
J-B. Rinaudo  settled this point experimentally by irradiating a piece of ancient linen of known historical age with a neutron flow in a reactor, and then measuring the radiocarbon age. He found, as predicted, that the apparent age of the cloth had been greatly advanced by the neutrons in accordance with the predictions, thus proving that the new C14 atoms produced by the neutron flow did indeed bind to his test sample of linen and remained there to alter the radiocarbon date.
If the Shroud’s real origin is 33 A.D. then this obviously would require an enhancement by a further 357– 33 = 324 years. A preliminary calculation, which is reserved for a later paper, shows that an enhancement of this amount is within the physical limits of the neutron flow and energy release which could accompany a certain non-violent nuclear transformation of matter.
10. Further radiocarbon testing ? Unless the problem of contamination in radiocarbon tests can be managed more accurately there is no point in any further carbon-14 dating; it has definitely already shown that the Shroud is ancient and that is about far as it can go.
Tests on the one-half piece of the 7 sq. cm cutting, which was not used in 1988 and is kept in Turin (Fig.1), corrected for the contamination, will obviously only give the same general result of “ ancient” age for the Shroud already now established from the other half-piece. Moreover, it would needlessly destroy a precious sample of the Shroud which may well be invaluable in some future scientific test on some questions other then than the Shroud’s age or authenticity which are now well established.
Charred pieces from the 1532 fire were removed from beneath the patches in the repairs made in 2003, and are kept at Turin, Radiocarbon dating tests on these charred remnants have been proposed. These would obviously prove to be even more difficult to relate to a reliable historical age than those from the 1988 contaminated corner pieces. In any case, radiocarbon tests can now only serve to further verify the certainly ancient, and most likely 1st century origin of the Shroud which has already been solidly established by a century of work in dozens of scholarly and scientific fields, and also by the properly calculated results of the 1988 C14 tests on the contaminated samples. That should settle the matter.
Copyright © 2004 Bernard A. Power