Section outline

  • Kia Ora Welcome to Week 3

    WALT: We are learning to test our materials to select the most appropriate solution for our tool box.

    Testing finishes (Scratch test)

    Beginning with one of the softer pencils, hold it as you would for writing and push it forward an inch or two across the finish. Maintaining equal pressure, follow with pencils of increasing hardness until you find one that cuts into the finish. The hardness rating for that finish is the rating of the previous pencil – the hardest lead that doesn’t cut.

    Water resistance

    Another quality you may want is water resistance. All finishes are more water resistant the thicker they are applied. So testing won’t be very revealing except on thin finishes such as oil or wax, or any film-building finish applied with just one or two coats.

    To test for water resistance, make up a sample board with the same number of coats applied in the same manner as you intend to use on your project. Then place a small puddle of water on the surface and cover it with a metal or glass cup or jar to prevent evaporation. Check every 10 minutes or so until you notice cracks or discoloration in the finish. Rate the finish at the most recent previous time before the damage occurred.

    Glue Test (Adhesion)