Another problem is that only very small samples can be taken so that the pictographs are not badly damaged. Therefore, a really sensitive technique is necessary to measure the carbon-14. We and others around the world have been attempting to do this for the last five years. Our method is unique because we use an oxygen plasma to remove the organic matter from pictograph samples. Plasmas are gases with equal numbers of positive ions and electrons.
Lightning flashes are plasmas, so are neon and fluorescent lights.
This is important because at high temperatures, the pictograph sample would be contaminated from the decomposition of the rock itself. After we expose a pictograph sample to the oxygen plasma, the carbon dioxide produced is separated from the remaining pigment and rock. This measurement gives the age of the painting. One of the pictographs we dated using our oxygen plasma is called the All American Man. It is a red, white and blue shield-bearing figure located in a rock shelter in Canyonlands National Park in southeastern Utah.