This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
Small blocks of wood can be hardened so that they will not split so easily when small screws are inserted by boiling them in olive oil for about 10 minutes. The olive oil can be kept for future use. If it is desired to waterproof the blocks after hardening them, they should be placed in melted paraffin and allowed to cool in the solution. This gives the block of wood a good appearance and makes it nonabrasive and waterproof.