We do not recommend dating the mortar directly, only organic materials recovered from it.
Carbon Dating Services
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When requesting for a formal estimate or quote, please let us know the number of samples for analyses, AMS service selected (Standard, Priority or Time Guide), and billing information (name and address of the paying institution).
Fees are inclusive of quality assurance reports, calendar calibration when applicable, and 24/7 web access to past results and pending analyses.
Pretreatment – It is important to understand the pretreatment applied to samples since they directly affect the final result. You are welcome to contact us to discuss the pretreatment or request that we contact you after the pretreatment (and prior to dating).
The following are listed in order of Beta Analytic’s recommendations:
1 – Date the organic material extracted from lime mortar
Radiocarbon dating of this type is possible provided there is sufficient amounts of wood, charcoal or other plant remains that can be found. The accuracy will depend on what organic materials are extracted, and if they were contemporary to the time of the construction. If wood or charcoal found in the mortar was from “old” trees, then there will be “X” years bias in the result based on how old was the carbon in the trees.
2 – Date the lime mortar directly
It’s also possible to date lime mortar directly but not usually from items exposed to the elements because the mortar will react with rain or groundwater to uptake carbon in the form of dissolved inorganic carbonates. Dating of lime mortar or plaster is very problematic and yields highly variable results even when the material has not been exposed to groundwater or rain water. For these reasons, we would not recommend dating the mortar directly, only organics recovered from it.
NOTE: Samples that date more recently than about 1650 AD produce multiple calibration ranges. This is due to their statistical overlap with the onset of the industrial revolution (and the release of large-scale fossil fuels) and above ground nuclear weapons testing of the mid 1950-1960 period.
AMS dating will be required for any samples sent due to the small amount of carbon that will be available. The lab needs between 1-4 mg of charcoal or 2- 5 mg of uncharred wood or plant post-cleaning and pretreatment and complete removal of the lime mortar by acid digestion. It’s hard to know how much mortar is needed to be sent; it will depend on the amount of charred or plant material present in any one chunk of mortar.
If you would like to date directly the mortar or plaster, please call the laboratory or email us at lab@radiocarbon.com before sending your sample(s).
Image credit: Berrucomons (licensed under CC BY-SA 3.0)
