Caulking won’t seal like it’s supposed to if it’s not applied correctly. Make sure you are always using the right techniques with sealant so you don’t have to redo the job to get it right.
Step 1 - Cutting the Nozzle
Embossed markings are located on each tapered caulk cartridge nozzle that correspond to the size of the bead that will be dispensed when the nozzle is cut there. By cutting the nozzle at different measurements, you can form a caulking bead to match your joint size. It's easy—just cut the nozzle at a 45-degree angle, place the tube in a caulking gun, and you're ready to begin (most cartridges also have an internal foil patch at the base of the nozzle that needs to be punctured with a nail).
Step 2 - Getting Started
Before you actually start to caulk, do some tests on newspaper or a paper towel to get a better feel for how the product dispenses. It is especially important to get the feel for keeping the caulking gun moving smoothly as you complete one stroke of the trigger and begin the next stroke. Once you've run a few inches or feet of caulk and have a good sense of what to expect, then start your first caulking effort on a part of your project that is relatively out of the way and unnoticed. Then, hopefully by the time you get to those portions of the job that are more conspicuous, you will have developed a good level of skill and your results will show it.
Tip: It is far better to pull the caulk tube nozzle along the joint than to push it. Pulling it allows the nozzle to smoothly slide over any obstructions on the surfaces being caulked, while pushing usually leads to more hang-ups and sudden stops, with attendant "blobs" of caulk occurring. Keep in mind that if you mess up a section of a bead, you can scrape it out right away and start over.
Step 3 - Applying a Bead of Caulk
As you apply the sealant, hold the caulking gun at a 45-degree angle to the joint being filled. Orient the nozzle opening so that it forces sealant into intimate contact with the joint surfaces. As you finish applying each bead of sealant, relieve the pressure inside the tube by releasing the trigger and pulling back on the rod to stop the flow of caulk. Releasing the trigger alone will not stop the caulk from flowing out of the nozzle. Apply only about two to three feet of caulk bead at a time so that you will have enough time to get it "tooled" before it begins to develop a skin (which then makes tooling difficult or impossible).
Step 4 - The Art of Tooling
Tooling is the process of gliding over the entire length of the applied bead of caulk in order to smooth it out and further force the thick caulk into enough intimate surface contact to establish good adhesion. Tooling can be done with a finger—covered with a latex glove, wetted with some water or solvent, or just bare, depending on the caulk used—or with various tools like a spoon, shaped piece of wood or a foam paint brush. It is important to avoid scraping an excessive amount of caulk out of the joint during tooling so you don’t starve the joint for sealant and waste a lot of caulk. Keep rags handy to clean up any mishaps, and clean up any problem areas right away since it is much more difficult to remove dried caulk later. If masking tape is used along the sides of the joint, make sure the tape is removed immediately after tooling is complete and before the caulk skins over so that it will pull away cleanly and leave a smooth, even line.
Tip: Caulk is made not to flow, so tooling is critical to force it into good contact with the substrate.
Article by Do It Yourself website http://www.doityourself.com/stry/applysealantproperly