Fill a tea kettle with water, and heat the water until it boils.
Place a large, rectangular cake pan on top of a table. Make certain the cake pan is wide enough to cover the area of caning in the dining room chair.
Place the chair upside down, or else on its back, on top of the cake pan, so that the sagging caning is lower than the pan's top edges.
Pour the hot water from the tea kettle onto the caning until the cake pan underneath it fills up submerging the caning. Place a towel on top of the caning to weigh it down, and pour the water on top of the towel, if this is necessary, to keep the caning submerged in the water. Leave the chair in this submerged position for five minutes.
Lift up the chair, and set it on the floor. Wipe the wooden chair frame dry, using a towel. Allow the caning 24 hours to fully dry and shrink before anyone sits in the chair.