New Treatment Halts Deterioration

Woodshop News, April, 1999
By A.J. Hamler

Few things are as frustrating as completing a project, only to have cracks appear in the wood as it dries. To prevent cracking, woodworkers – especially turners – have traditionally treated green wood with a chemical solution known as PEG (polyethylene glycol). According to Preservation Solutions, its new wood treatment called Pentacryl works faster and is less expensive to use than PEG.

While Pentacryl is now being marketed to woodworkers, Dale Knobloch, founder of the Golden, CO-based company, said the wood treatment was developed to preserve a number of ancient American Indian artifacts. The Maine State Museum in Augusta had found a number of Indian weir stakes in a lake, and took several of them out that ranged anywhere from 3,000 to 6,000 years old,” Knobloch said, adding the museum had hired another company to treat them with PEG. Although the PEG was working as a preservative, he said the process was both expensive and time consuming.

“The first of three stages of treatment cost in excess of $40,000 for 26 of them, and they were just finishing them up after three years. They gave us some to work on, and those we did for a fraction of the cost and had them back to the museum in two months.”

Knobloch has used Pentacryl on other artifacts for the museum, including a dugout canoe that came from the bottom of a lake, and several oak posts recovered from the Popham colony settled in Maine in 1607, at the same time as Jamestown in Virginia.

Had the artifacts not been treated, Knobloch said, they would most likely have begun to crack as they dried, just as green wood does in wood-working situations. He said the cracking is caused when cells in the wood collapse as water leaves the wood during the drying process. The siliconized polymers in Pentacryl penetrate into the wood, coating the cells and keeping them from collapsing.

Pentacryl can be applied in one of two ways. Small wood pieces can be soaked in a container of the solution, with the remaining solution saved. Larger pieces can be treated by brushing on the solution until the wood is saturated. For turnings such as bowls and other objects where a great deal of stock is being removed, Knobloch recommends a rough turning be done first. Not only will this conserve the solution, he said, but the solution penetrates the wood more easily and
quickly when the turning is closer to the finished dimensions.

According to Knobloch, the amount of Pentacryl needed for a particular work piece varies. “It depends on the type of wood,” he said. “For soft, open-pore wood it could take as much as 8 ounces per board foot. Very dense wood may only take an ounce per board foot.”
This oak post was recovered from the site of the Popham Colony in Maine, and treated with Pentacryl to prevent it from cracking and deteriorating after it was unearthed. The founders of the colony, which was established in 1607, buried these posts in the ground as foundations for barns and other structures.

As with PEG, Pentacryl will slightly increase the density of the wood when dry. According to Preservation Solutions, a cubic foot of wood (12 bf) will weigh about 10-12 oz. more than the same wood un-treated. Knobloch said Pentacryl is nontoxic, and completed projects can be finished normally with any conventional coating. Available through retail and catalog outlets.