Pine tar can sometimes be thinned for easier brushing, but the thinner must suit the product and the project. Many craft finishes use tar with oil or a compatible solvent, tested first on scrap material.
Pine tar can be thick, especially in cold weather. Thinning makes it easier to brush, helps it wet the timber surface, and can produce a less sticky finish. The important point is that not every pine tar product is meant to be thinned in the same way, and not every craft object benefits from a thinner coat.
Traditional mixtures often combine pine tar with linseed oil, turpentine, or another suitable thinner, but the exact blend depends on the material and the intended finish. A small test is more reliable than a universal recipe. The test should show whether the mixture darkens evenly, penetrates properly, dries down acceptably, and remains compatible with any later maintenance coat.
Work in ventilation and keep thinned tar away from flame, sparks, and indoor living spaces. Thinners change smell, drying behaviour, and flammability. A thin mixture can also spread farther than expected, so protect surrounding surfaces and avoid using it on anything that must stay clean or food-safe.