Have you ever experienced the frustration of bubbles that appear in your finish as it dries? This may be caused by the temperature changes in the wood while the finish is curing.
Usually, bubbles in a finish are caused by rough brushing during the application process. Finishes that take longer to cure can allow the bubbles to work their way out. Sometimes though there can be another culprit - heat.
The surface of wood is made of microscopic pores and tubes that were used to carry water and nutrients up the tree. When the wood is cut and dried the water is removed from these tubes and air fills them. The problem starts when you turn on the heat in your shop and begin applying the finish.
As the wood warms up the air is pushes out of the pores and into the finish - leaving bubbles. The solution to this problem is simple, make sure the wood is warm and at a constant temperature during the finishing and curing process.
Note: There is also a school of thought that prior to finishing, the room should be over-heated. After the finish is applied the room is allowed to slowly cool. The thought is that this will help to pull the first coat of the finish into the wood thus creating a stronger foundation for subsequent coats. The success of this process will depend on the wood being finished as well as the viscosity of the finish being applied. If you've used this technique let us know how it turned out.