Can anyone help please, i have made some raised planters in my back garden with old reclaimed railway sleepers. Being a bit of a novice i didnt realise in the sun they would leak tar and other nasty stuff, does anyone know of a way of sealing them, or any other way of masking the tar. I have thought about tiling over the bad bits with some cheap terracotta tiles but vant find an adhesive strong enough to do the job.......please someone help!!!!