David has just bought a pine shelf from B&Q for his 'summer house', a small wooden shed in the garden, which is used as the 'warm room' for the observatory complex.
The shed has MANY glass windows and thin wooden walls. It's fairly watertight. Solar gain means temperatures can peak at around 40C but the shed's situation at far end of the garden mean its night time minimum temperature is a couple of degrees below that closer to the house. David heats his warm room with an electric convector when he observes in the winter. I suspect there are also HUGE fluctuations in humidity in this shed.
He has a similar shelf he varnished with PU a few years ago. The varnish has turned to powder and is clearly unsuitable!
Should he paint/treat/stain the wood or leave it well alone?