To tar outdoor furniture, use a thin pine tar finish on suitable exterior timber, avoid seating surfaces that will stain clothes, and let the treated wood settle fully before use.
Tar can suit rustic benches, garden tables, stools, and outdoor timber furniture where a dark traditional finish is wanted. It is most practical on pieces that live outside, have rough or simple construction, and are not expected to behave like clean indoor furniture. Fresh tar can smell, mark fabric, and hold dust if applied too heavily.
Clean the furniture and let it dry thoroughly. Brush a small test patch first, because tar can darken wood dramatically and unevenly. Legs, feet, underside rails, end grain, and backs often benefit more than the actual sitting surface. On seats, armrests, and tabletops, a very light coat or a different compatible finish may be more practical if people will touch the surface often.
Tarred outdoor furniture ages with weather. It may become duller, less sticky, and more grey-black over time. Renew the coating before bare wood becomes exposed, but do not keep adding heavy coats to surfaces that people sit on or lean against. The best result is protective without feeling wet.