How Do You Date Mortar?
Image idea: a scientist working in a laboratory.
The team sent the mortar samples to a lab. They used a method called optically stimulated luminescence, or OSL.
OSL measures when tiny grains of quartz in the mortar last saw light. Once the mortar was sealed in darkness, that “clock” started ticking. The tests took about a year.
Archaeologists use this method to date materials that other methods, such as carbon dating, cannot handle well. It works especially well for building materials like mortar and sand.