You may have left them in the shade, where they became damp and weakened. Or you may have left them in the hot sunshine, where they became dry and brittle. Though bamboo Chippendale chairs look — and also to a large extent, are resilient, they’re not indestructible. With a couple of simple steps, you can save your bamboo chairs in the harshness of the outside. You may not be able to fully restore them to their initial state, but you need to be able to come near.
Set the chair on an old blanket or dropcloth in a well-ventilated location.
Remove dirt from the chair using a rag or the vacuum. Blend 1/2 gallon of soapy water and a couple of tsp of ammonia, and wash the chair using a soft sponge. Rinse with a damp sponge and cool water. Blot the chair dry using a clean rag.
Repair any cracks in the bamboo by trimming trouble spots with fine-grit sandpaper. Remove the dust with tack cloth. Then rub the chair using a paste wax, or use linseed oil or furniture oil specifically created for bamboo furniture.
Apply a coat of lacquer to protect the finish. Pick from a brush-on or spray variety to produce a tough and lasting effect.