The stair spindles are the ornamental pieces between the handrail and the steps or stringer on a staircase. Stair spindles come in many styles. They incorporate flat planes, cylindrical sections, fluted surfaces, doughnut shaped areas, barley twists and other decorative details. You should sand by hand rather than using an electric sander, according to Roy Barnhart of This Old House.
Wrap medium grit sand paper around the sanding block. This is appropriate for bare wood and gentle varnish removal. Sand flat surfaces with an up and down motion, staying on the flat plane. This way, you will follow the grain of the wood and not produce any cross-grain scratches. Take care not to slip the sanding block off the flat plane and over a corner. This may spoil the integrity of the corner profile. Do all four flat sides of a square section the same way.
Sand cylindrical surfaces with more care as they are more difficult to sand than a straightforward flat surface. Hold a piece of sand paper by two edges, around the cylindrical section. Move your hands alternately backwards and forwards. Barnhart describes the action is like shining a shoe. For tight spaces, carpenter Peter Brett suggests applying pressure to the sand paper with fingertips.
Sand barley twist sections with even greater care, so you don’t damage the intricate design. Cut a strip of sand paper, place it around the section and aim to buff-sand the surface. Vary your sanding angle as you work so you don’t make grooves with the edges of the strips. Fit a strip edgewise into any crevices and work it back and forth a few times to ensure you sand all parts.
When sanding a whole staircase of spindles, start from the top of the staircase -- rather than the bottom -- so dust falls downwards, away from you.
Wear a safety mask and goggles when sanding.