One method for quickly adding heat and moisture to small pieces of wood is to use a microwave oven. As long as the wood and a means of keeping the wood moist can fit into the oven, this is an extremely efficient method for softening wood. Through experimentation, I have found there are several things to take into consideration when steaming wood in a microwave oven.
A microwave oven works by focusing tightly shaped radio waves on the water molecules within whatever is placed inside the oven. The molecules become slightly agitated and as a result, they give off heat. A dried piece of wood will heat up quickly when placed into the oven because it still contains enough water molecules to create heat. When the wood is removed, it is very hot, but it dries out very quickly because the water molecules have broken down and so they easily evaporate. This process actually makes a microwave oven a good tool for drying small pieces of wood for turning and other small projects – but only if the moisture content is lowered slowly enough to prevent cracking.
To make the microwave useful for bending, you need to add some moisture to the equation, just as you do when steaming wood. There only needs to be enough water present to surround the wood. Any extra water will just slow down the process. Wood can be wrapped in a soaking wet rag or placed in a shallow microwave-safe bowl with just enough water to cover the wood. There is no set time for heating wood in a microwave, so a little trial and error will be needed. Usually 5 to 10 minutes will do the trick. Keep a close eye on the progress, because if all of the water evaporates and the wood continues to heat, it could catch on fire.
Another thing I discovered in my experiments is green wood has enough moisture in it to be heated without additional water. However, overheating it will dry the wood too much.
Whatever method you use to heat the wood in a microwave, you will need to use a good form and a compression strap for the wood to bend properly.