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The tar varied in quality—early flow being thinner and lighter, late flow thicker and darker, properties affecting suitability for different applications.
The Grades:
“Pitch” or pine tar was raw product—relatively thin, dark brown to black, viscous but flowable at room temperature. This was standard waterproofing material, rope treatment, general-purpose tar.
“Stockholm tar”—premium grade from Sweden—achieved fame for exceptional quality, became specification standard, commanded higher prices. The quality came from careful wood selection, optimal processing, rigorous quality control.
The Characteristics:
Good tar was thick enough to coat surfaces effectively but thin enough to apply easily, dark colored, had characteristic pine smell, didn’t crystallize or separate on storage, remained flexible rather than becoming brittle.
Poor tar was thin (high water content), light colored (insufficient heating), contained excessive particulates, separated into layers on standing, or became too stiff to use.
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