C-14 dating
 

Hi All

Searching the archive here on Turkotek I see that there in 1999-2000 was an extensive and rather heated discussion regarding c-14 dating of rugs. I wonder if anyone knows if there has been any development in the c-14 techniques regarding rugs since then?

Here is a link to a university in DK which offers AMS c-14 analysis for a fee that is less then what I would have expected: http://www.phys.au.dk/ams/servav.shtm

Martin

Here's a link to the Salon to which Martin refers.
http://www.turkotek.com/salon_00021/salon.html

I also moved the thread from "Show and Tell" to "Miscellaneous Topics".

Steve Price

Hi Martin

I believe the best laboratories are now able to achieve precisions of plus or minus 25 years (a 50 year range with the mean in the middle of it). Samples from rugs present no special problems that aren't common to any other biologically derived material. Exhaustive washing to remove contaminating materials (smoke residues can cause serious dating errors, for example) is important, but every competent laboratory using C-14 knows this.

Regards.

Steve Price

Hi Steve

Thanks, nice knowing that washing a rug doesn’t ruin the possibility of a c-14 dating.

I have contacted the University in DK, and if they offer the service for private persons, I will probably give it a try on the Torba we discussed in the other tread. According to their homepage it may take 6 months for them to run the tests. What ever the result may be it will be interesting, and I will return with the results.

Regards
Martin

That plus or minus 25 years doesn't seem right. If I recall Jurg Rageth's presentation correctly, the idea is to correlate the percentage of C14 in the sample with the known historical population percentage of C14 in the atmosphere over time. But that population percentage is a a non-monotonic curve, so there might have been several periods of time when the percentage was the same. So you might get an assessment like "The sample originated between years A and B with X percent likelihood, between years C and D with Y percent likelihood and between years E and F with Z percent likelihood." Maybe someone with a copy of Rageth's book or his paper can give a better answer.

niggling correction
 

To be accurate, what is confusing is not that the C14 concentration in the atmosphere was the same at different times in the past (in fact, it would have been ideal had it been always the same!), but rather that the residual at the present time (resulting from the decay of what was there at the formation time) can be the same in spite of different formation times.

Of course, before commiting oneself to carbon dating a piece, one should have a reasonable expectation that the piece is over 200 years old. The results for newer pieces are near worthless.

Steve, If memory doesn't fail me, during the earlier discussion you were totally negative about the value of carbon dating rugs. What has led you to recondider?

Regards, Yon

Hi all,

From the for-what-it's-worth department, I've had good luck with archaeological specimens using Dr. Alan Hogg's AMS radiocarbon lab at University of Waikato, in Hamilton New Zeealand.

Here's a link to their site:
http://www.radiocarbondating.com/

and, an ancillary site that they contribute to, with a lot of good info and links:
http://c14.arch.ox.ac.uk/embed.php?File=dating.html

Regards,
Chuck Wagner

Hi Yon

My negativity toward C-14 rug dating was based on the contamination problem. Traces of smoke can add hundreds of years to the apparent age of a sample, and rugs were routinely exposed to smoke, especially if they were in nomad tents. The contamination problem is now widely recognized by the folks who run C-14 labs, and every sample is washed exhaustively. I don't know how recently this practice was instituted; my information a few years ago may have been out of date when I wrote it.

Regards,

Steve Price

PS: I just went through some of the links Chuck posted. This one, http://www.c14dating.com/int.html , notes that a number of laboratories (including the New Zealand and Arizona labs) now use methods that provide dates with 95% intervals as low as 32 years (plus or minus 16 years of the mean).