Silver birch wood is pale in colour with no distinct heartwood and is used in making furniture, plywood, veneers, parquet blocks, skis, and kitchen utensils, and in turnery. It makes a good firewood, but is quickly consumed by the flames. Slabs of bark are used for making roof shingles and strips are used for handicrafts such as bast shoes and small containers. Historically, the bark was used for tanning. Bark can be heated and the resin collected; the resin is an excellent waterproof glue and useful for starting fires. The thin sheets of bark that peel off young wood contain a waxy resin and are easy to ignite even when wet. The dead twigs are also useful as kindling for outdoor fires. The removal of bark was at one time so widespread that Carl Linnaeus expressed his concern for the survival of the woodlands.