PEGcon is an easy-to-use two part DOS program that helps to calculate how much polyethylene glycol to use to conserve waterlogged wood. The first part provides you with the final concentrations of PEG to treat your wood. This calculation will tell you how much of each grade of PEG to put into the impregnating tank. It is intended to be used as a method of calculating appropriate PEG concentrations and allowance is made so that any ratio of PEG to cell wall can be obtained. The calculation is based on the aim of filling the second order space in the residual wood cell-wall with PEG 200 (or 400) and adding an amount of PEG 3350 equal to the volume of cell-wall missing through deterioration.
The second part is designed to aid you in making up and changing the PEG solutions. It determines how much solution to remove when you increase the concentration of the high molecular weight component. Obviously it is desirable to waste the minimum PEG, and it is also important to keep the solution volume constant throughout. This method is based on the understanding that the treatment commences with a PEG 200(400) solution, the concentration of which remains constant throughout the impregnation. When the initial phase of the treatment is complete, and it is time to start adding the higher molecular weight PEG, a certain volume of solution is poured out and replaced with an equal volume of a mixture of PEG 200(400) and 3350 (more PEG 200(400) must be added to keep the concentration constant).
For further information about this technique, there is a published manuscript available in Cook, Clifford and Grattan, David W., "A Method of Calculating the Concentration of PEG for Freeze-drying Waterlogged Wood." in: Proceedings of the 4th ICOM Group on Wet Organic Archaeological Materials Conference, Bremerhaven, 1990; Per Hoffmann, editor; ICOM Committee for Conservation Working Group on Wet Organic Materials, Bremerhaven, 1991.
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