Mt Dad is indulging in a bit of old style boat modelling. Using a 1950s plan (still available) for a boat called "Water Bug", he's busy with balsa wood doing some scratchbuilding.
Waterproofing the wood involves several coats of "sanding sealer". This soaks into the grain and hardens it up. A quick sand between each coat and the surface is converted from the soft and spongy balsa to a smooth and hard, almost resin like finish.
The smell (of cellulose dope) is wonderful too, best not appreciated anywhere other than in a well ventilated room though!
