The <i>Bremen Cog</i> was salvaged in 1962. First proposals were to use PEG 1000 but early results on components of elm, beech, and oak were disappointing. Instead excellent results were obtained using a two-stage process with two separate periods of immersion: first in PEG of low molecular weight and then in PEG of high molecuar weight. Impregnation began in 1985, first with PEG 200. PEG 3000 will be used for the second period of immersion. A mechanism for the two-stage impregnation is proposed.