Frequently Asked Questions

Understanding and interpreting data

What is the half-life of 14C? What is the Libby half-life?

The currently accepted half-life of 14C is 5,730 years, and is referred to as the Cambridge half-life. The Libby half-life is 5,568 years, and is accepted as incorrect. Following tradition, the Libby half-life is still used to calculate standard radiocarbon ages. Read more on this topic on the understanding units page.

What is a standard radiocarbon age and how is it different than a calibrated age?

A standard radiocarbon age is not reflective of the true age of a sample. It is calculated using the incorrect half-life of radiocarbon (Libby half-life), and does not take into account variation in atmospheric radiocarbon production through time (wiggles in radiocarbon calibration curves).Calibrated, or calendar, ages are a reflection of the real age of a sample to the best of our knowledge, are calculated using the correct half-life of radiocarbon and utilize calibration curves. Read more on this topic on the understanding units  and calibrated dates pages.

Why is the time span of my calibrated date so large?

Pre-bomb radiocarbon production in the atmosphere fluctuated around an average value, due to the influence of things like ocean circulation, sun spots, and fossil fuel emissions. These "wiggles" introduce uncertainty into the calibration process and may result in low precision for calibrated ages.

Sample submission and handling

What can I date?

Any carbon containing material less than 60,000 years old.

My samples are composites of different carbonaceous materials, do I just send it all?

Generally, the answer is no. Most labs require the sample for graphitization to be isolated from bulk materials prior to graphitization, but this can be discussed with a radiocarbon mentor or the graphite lab you plan on submitting to. 

How much sample do I send?

Graphite samples generally contain ~1 mg of C. Check the submission guidelines of the graphite lab you are submitting to.

Is there a minimum amount of sample I can send?

Yes. Some labs can analyze samples as small as 10 µm, but many labs have larger minimum samples sizes.

How should I send it?

Samples can be wrapped in clean foil and placed in a clean vial, or ziplock bag. Samples can also placed directly in a clean vial. Please use glass vials if possible. Static electricity can wreak havoc with smaller samples placed directly (not wrapped in foil) in plastic vials or plastic bags.

How do I know if my samples need pretreatments?

Most samples do require some sort of pretreatment. Please consult our sample prep guiding materials and discuss specifics with your lab of submission.

How much does the service cost?

Cost varies widely with sample type and lab of submission, from $99 to over $600. Some labs have prices listed online, some do not. Please see our find a graphite lab page for further information.

How do I know if my lab is clean?

If this is your first submission of radiocarbon samples and your lab has not been swiped for radiocarbon contamination please inform you lab of submission. Some labs require proof of cleanliness prior to submission, some do not.