PAINTED WOODEN BLOCKSMost wooden blocks designed to show strata with various structures are best made from PAR (=planed all round) timber. The best size for the painted blocks is 50mm by 100mm by 150mm. Buy timber with a cross-section 50mm by 100mm. You should choose timber with as few knots as possible. Cut the timber into 150mm lengths and sand the ends you have cut and the edges. Make sure there a no splinters.If there are knots or sap hollows paint them with two coats of knotting.Paint the wood on all sides, top and bottom with a white undercoat or primer.Mark in pencil the lines of the strata or faults. A woodworking square or a set square, a parallel rule and a sliding bevel are useful.It is easiest if, where possible, you paint upper beds first then runs can be painted over with the next colour. Use small brushes. Use gloss paint.Paint one colour on all the blocks at once then the paint on the first will have begun to dry before you start the next colour. Or better leave the blocks overnight before you start the next colour. Once all the blocks are painted put on a north sign, usually parallel to one long edge. Then add a number if appropriate.