There are a few things you can do to clean unsealed slate when you’re working with slate:

  1. Use a mild soap and water to clean the slate. This will remove any built-up dirt, dust, and other debris that may have been on the slate.
  2. Use a dry cloth to clean the slate. This will remove any oils, waxes, and other chemicals that may have been on the slate.
  3. Use a vacuum cleaner to clean the slate. This will remove any trapped air pockets and any other debris that may have been on the slate.