Do it yourself: caulking tips and techniques when painting exteriors
Caulking compound comes in standard tubes that are designed to dispense their contents when fitted into a special caulking "gun." The most commonly used caulking guns are manual devices ranging from about three dollars to ten dollars in price. These are adequate for almost all home caulking jobs. Professionals sometimes use pneumatic caulking guns, and these are fine if you happen to have a compressor handy anyway, but don't go out and buy all this equipment when the cheap manual gun will do the job.
Caulking is applied to the joints between wood parts in a "bead," which is a continuous stream of caulk laid on the joint by squeezing the trigger of the gun and moving the tip of the caulk tube simultaneously. The key to getting the correct size bead of caulk is cutting the tip of the tube to the proper size and angle. The caulk tube comes with a tapering tip, allowing you to cut it so that the opening diameter ranges from less than an eighth of an inch up to about three eights. A medium-sized opening of about one quarter inch or less seems to work best for most caulk applications. It is also important to cut this tip off of the tube at an angle of about thirty degrees. This allows the caulk to flow better and gives you more control. Cut caulk tubes with a razor blade or box cutter for a clean, smooth cut.
Most beginners make a big mess when trying to apply caulking. It is an inherently messy job to begin with, so it is essential to have plenty of rags or paper towels on hand to clean up and to wipe your hands. To do a good job of caulking, you will need to get your hands messy, as it is necessary to smooth out the caulk bead with a finger tip. Many people fail to do this, and that is why they do not get a good, watertight seal in their caulk joints. The trick is to lay the bead of caulk along the joint with the caulk gun, and then immediately come back with your index finger, pulling it along the length of the caulk bead so that it flattens and smears the caulk, also forcing it deeply into the seam. Large open joints may require two or more applications. Wait until the first is dry before coming back though, as caulking compounds do not do well when dabbed on too thickly.
When painting a house, particularly the exterior, it is essential that you caulk every crack, seam or gap you can find in the woodwork. Openings such as these, if left un-caulked, will admit rain water and other moisture into the wood and inside the house, causing mildew and eventually wood decay that will require the services of a carpenter. Insects and other pests can also get inside your attic or in your walls through such seams. Wasps, in particular, are fond of such cracks that allow them to build their nests inside cornices and in attics.
One trick to finding all the smallest cracks and open seams is to go ahead and apply the first coat of paint on all the wood before you begin caulking. The freshly painted surfaces will highlight any openings, even small nail holes, so that you can see them all and caulk them. The other advantage is that the caulk will adhere better to the clean surface of newly painted wood. Just make sure the paint is dry first.
Proper caulking will vastly improve the appearance of any paint job, giving it that professional touch most do-it-yourselfers never achieve. The other benefit is that your home will be tightly sealed and better protected.