Modern sealant should last longer, still look authentic
By Tom Vogt, Columbian
Science, Military & History Reporter
Published: October 5, 2012, 5:00pm
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Cary Porter, a maintenance worker at Fort Vancouver National Historic Site, uses a spoon as a tool for smoothing sealant Friday as part of a re-chinking project at the two-story fur store. The blue material is masking tape.
Reconstruction began in 1966 at Fort Vancouver National Historic Site, 1001 E. Fifth St.
In the Hudson’s Bay Company era, the massive timbers of Fort Vancouver’s fur store safeguarded valuable animal pelts.
Protection included keeping out wind and rain.
Today, the replica structure is a storehouse for precious museum artifacts. But some of the threats haven’t changed in 170 years.
“Moisture and wind are things we still want to keep out of the building today,” said Alex Patterson, facilities supervisor at the Fort Vancouver National Historic Site.
Building big wooden-timbered structures has built-in issues, he explained.
“Wood tends to move and shift with the environment. There is curing and shrinking,” Patterson said.
When a building goes up, the biggest gaps between the timbers are about three-quarters of an inch. At the fort’s carpenter shop, which recently was re-chinked, “Some of the gaps were up to three inches,” he said.
In the 1800s, builders would use materials like rope, clay and straw to fill the cracks between the horizontal timbers, Patterson said. When it came time for his staff to take on the task, Patterson knew they needed something better.
“Rather than using straw or clay to seal the gaps, we had to come up with a more advanced solution that lasts longer,” he said.
A local company provided a hybrid polyurethane/silicone sealant that will do the trick — protect the buildings, maintain the historic appearance and provide much better durability, Patterson said.
Cary Porter, a National Park Service maintenance worker, said a couple of different techniques provide the finishing touches.
Depending on the width of the gap, “You use different-sized spoons to smooth the sealant,” Porter said.
“Brushing on a sandy mortar takes off the shine,” Porter said.
