Guaiacol is a wonderfully smoky, vanilla and phenolic chemical which can contribute enormously to a natural vanilla type base when blended with Vanillin or Ethyl Vanillin. Use it for a smoke note when Birch Tar is a little too powerful for your needs or exploit its phenolic qualities in an otherworldly modernist scent. Guaiacol is very powerful so you may wish to dilute it to 10% or even 1%.