Scrape off as much of the tar as possible. Use a spoon or a dull knife for this purpose. But before you do so, it would be a good idea to freeze the tar using ice cubes. This will make it easier to get rid of excess tar.
In order to get rid of the remaining tar residue from the piece of fabric, lubricate the stain. There are a number of lubricants you can use for this purpose. These include WD-40, lard, bacon grease, vegetable oil, peanut butter, Goo Gone or Goof Off lubricants. Choose either one of these lubricants.
Apply a small quantity of the lubricant you chose in the earlier step onto a piece of clean, soft cloth and use it to blot the tar stain. Make sure that the stain is properly moistened before moving on to the next step. You may have to use more than one piece of cloth.
Then, actively rub lubricant into the stain by scrubbing the tarred fabric area. Allow enough time for the lubricant to settle properly so that it can loosen up the tar. For bigger stains, this step would require more time as compared to the time required for smaller tar stains.
Wash the fabric according to manufacturer’s instructions and check if you were able to remove the tar. You may have to repeat this process more than once before the tar can be removed from the fabric completely.