Calculate the PEG Concentration Required to Treat Wood Without Freeze-drying

As not all archaeological conservators that treat waterlogged wood have a freeze-dryer, Dr. Per Hoffmann has developed a method of treatment that does not require freeze-drying.(1) This process is a two-step PEG treatment followed by air-drying. The PEGcon program can be used to calculate the PEG concentrations required for Hoffmann's method.

This is accomplished by running the PEGcon program twice and calculating the PEG concentrations separately. In the first calculation the actual density of the object is set to equal the average density of normal wood of the same species. The result is the required concentration of PEG 400 to treat the object. In the second calculation the quantity of PEG 3350 is determined by setting the actual density to 0.1 and calculating again. In addition to the suggested PEG 3350 concentration, the program will also return a low value for PEG 400 %v/v which should be ignored.

The suggested PEG 400 concentration from the first calculation and the PEG 3350 concentration from the second calculation are the values that should be used to treat the wood. However, if the combined concentration is less then 70%, the PEG 3350 value should be increased above that suggested by the program so that the total PEG used is at least 70%.

(1) Per Hoffmann, "On the stabilization of waterlogged oakwood with PEG. II. Designing a two-step treatment for multiquality timbers", Studies in Conservation, vol. 31, no. 3, 1986, pp. 103-113.