There were two series of carbon dating

Radiocarbon dating

Radiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...

 tests performed on the Dead Sea Scrolls

Dead Sea scrolls

The Dead Sea Scrolls are a collection of 972 texts from the Hebrew Bible and extra-biblical documents found between 1947 and 1956 on the northwest shore of the Dead Sea, from which they derive their name...

, one series by the AMS (Accelerator Mass Spectrometry

Accelerator mass spectrometry

Accelerator mass spectrometry differs from other forms of mass spectrometry in that it accelerates ions to extraordinarily high kinetic energies before mass analysis. The special strength of AMS among the mass spectrometric methods is its power to separate a rare isotope from an abundant...

) lab of the Zurich Institute of Technology

ETH Zurich

The Swiss Federal Institute of Technology Zurich or ETH Zürich is an engineering, science, technology, mathematics and management university in the City of Zurich, Switzerland....

 in 1990 and a second by the AMS Facility at the University of Arizona

University of Arizona

The University of Arizona is a land-grant and space-grant public institution of higher education and research located in Tucson, Arizona, United States. The University of Arizona was the first university in the state of Arizona, founded in 1885...

 in Tucson in 1994. There was also a historical test of a piece of linen performed in 1950 by Willard Libby

Willard Libby

Willard Frank Libby was an American physical chemist noted for his role in the 1949 development of radiocarbon dating, a process which revolutionized archaeology....

, the inventor of the dating method.

14C Test results

The following table shows all the Qumran

Qumran

Qumran is an archaeological site in the West Bank. It is located on a dry plateau about a mile inland from the northwestern shore of the Dead Sea, near the Israeli settlement and kibbutz of Kalia...

-related samples that were tested by Zurich (Z), Tucson (T) and Libby (L). The column headed "14C Age" provides a raw age before 1950 for each sample tested. This represents the ideal date for the amount of 14C measured for the sample. However, as there is fluctuation from year to year as to the quantity of 14 absorbed by all life, the figure needs to be calibrated based on the known fluctuation. This calibrated range of dates is represented in the last column, given with a 2-sigma error rating, which means at 95% confidence. (Although the tests included documents which were not from Qumran, with the exception of the Wadi ed-Daliyeh deed these will not be listed below.)

The texts are ordered chronologically, based on their 14C age.

-	Lab	Description	14C Age	Calibrated Age (2-sigma)
1	Z	(Wadi-Daliyeh deed)	2289 +/- 55	408-203 BCE
2	Z	Testament of Qahat	2240 +/- 39	395-181 BCE
3	T	1QIsaiaha	2141 +/- 32	351-295 or 230-53 BCE
4	Z	Frg. 3 (from 4Q365?)	2139 +/- 32	351-296 or 230-53 BCE
5	Z	1QIsaiaha	2128 +/- 38	351-296 or 230-48 BCE
6	Z	4Q213 Levia ar	2125 +/- 24	344-324 or 203-53 BCE
7	T	4Q249 pap cryptA	2097 +/- 50	349-304 or 228 BCE-18 CE
8	Z	4Q53Samuelc	2095 +/- 49	349-318 or 228 BCE-18 CE
9	T	4Q208 (4QEnastrA)	2095 +/- 20	172-48 BCE
10	T	4Q267	2094 +/- 29	198-3 BCE
11	T	4Q317 Phases of the Moon	2084 +/- 30	196-1 BCE
12	T	1QpHab Habakkuk Commentary	2054 +/- 22	160-148 or 111 BCE-2 CE
13	T	4Q22 paleoExodusm	2044 +/- 65	342-324 or 203 BCE-83 CE or 105-115 CE
14	T	1QS Community Rule	2041 +/- 68	344-323 or 203 BCE-122 CE
15	Z	11Q19 Temple Scroll	2030 +/- 32	166 BCE-67 CE
16	T	4Q22 paleoExodusm patch	2024 +/- 39	161-146 or 113 BCE-70 CE
17	Z	1QApGen Genesis Apocryphon	2013 +/- 32	89 BCE-118 CE
18	T	4Q521 Messianic Apocalypse	1984 +/- 33	49 BCE-116 CE
19	Z	1QH Thanksgiving Scroll	1979 +/- 32	47 BCE-118 CE
20	T	4Q258 Comm. Rule, 2nd sample	1964 +/- 45	50 BCE-130 CE
21	T	4Q266 Damascus Documenta	1954 +/- 38	44 BCE-129 CE
22	T	4Q171 Psalms Commentarya	1944 +/- 23	3-126 CE
23	T	4Q258 Comm. Rule, 1st sample	1823 +/- 24	129-255 or 303-318 CE

 

24	T	Qumran 4Q Linen with leather thong	2069 +/- 40	197 BCE-46 CE
25	L	Qumran 1Q linen	1917 +/- 200	390 BCE-600 CE

Many of the date ranges provided are actually two date ranges, for example the Habakkuk Commentary (#12), which is given as 160-148 or 111-2 CE. The section of the calibration curve for the 14C age of the Habakkuk Commentary is complex, so that the 14C age of 2054 cuts through a few spikes on the curve, providing two date ranges.

Some Observations

The Great Isaiah Scroll 1QIsa^a was tested twice, once at Zurich and once at Tucson. The results were almost identical which was a good indicator of the basic accuracy of this dating method. 1QS (#14), tested at Zurich, and 4QSam^c (#8), tested at Tucson, provide overlapping date ranges, which is to be expected when both texts are attributed to the same scribe. When 4Q258 (#23) was tested at Tucson its result was so anomalous (129-255 or 303-318 CE) that the laboratory was asked to retest another sample from the same document. The second test (#20) yielded a result (50 BCE-130 CE) that was deemed more satisfactory.