Tar can sometimes be painted over, but it is often difficult. Tar may bleed through paint, remain sticky, repel coatings, or prevent proper adhesion unless the surface and primer are suitable.
Painting over tar is rarely as simple as painting over clean dry wood. Tar can contain oils and heavy compounds that migrate into later coatings. It can stay flexible, smell strongly, or soften in heat. A normal decorative paint may not bond well and may discolour as tar stains bleed through.
The answer depends heavily on the kind of tar. Weathered pine tar on outdoor timber is a different problem from roofing tar, bitumen, coal-tar coating, or an unknown black stain in an old building. Some surfaces need cleaning, ageing, specialist primers, or complete removal before painting is realistic.
In heritage work, painting over tar may also be the wrong goal. A traditional tarred surface might be meant to remain tarred and maintained with compatible material. Covering it with modern paint can trap moisture, create adhesion problems, or change the character of the object.
The safest general answer is that paint and tar often conflict. Test areas, product compatibility, and the existing surface matter. If the tar is unknown, contaminated, or structural, identify it before coating it.