DIY Caulking Techniques
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Before painting a room it's a good idea to caulk between trim molding and walls first. This will greatly improve the quality of the finished paint job. Take care when choosing caulk for wood trim and other painted surfaces. Use a paint–able latex or silicone enhanced caulk, not pure silicone, for painting projects. Pure silicone caulk will repel paint and should only be used for caulking bathroom tubs and tile and similar non–painted surfaces. Both types of caulk will set (become firm) in about an hour and cure (become hard) in about 24 hours. You can paint latex caulk after it has set but be careful not to dig into the bead with the brush bristles.
Clear the Crack
The first step to caulking is to remove any loose material from the gap between the two surfaces. Wedge a putty knife or similar tool between the wall and trim and drag it down the length of the crack to remove loose plaster and paint. Sometimes a putty knife can be slipped under the old caulk and the whole bead can be removed at once.
If the old caulk is cracked but not coming off, trim the crack out with a sharp drywall knife. Cut cleanly through the caulk but avoid cutting into wood trim or the wall surface and pull the loose caulk free. The gap to be filled with caulk should be no wider than about 3|8in. If you have spaces wider than this, insert a strip of wood with a little caulk applied, into the gap to fill the extra space or fill the gap with spray–foam insulation and then caulk.
Setup the Caulk Gun
Cut the applicator tip of a caulk tube at an angle far enough down to make about a ¼in. opening. There is a foil seal where the applicator tip meets the tube, pierce this with a long nail or the peircing rod included on some caulk guns. Insert the tube into a caulk gun and push the plunger down so it makes contact with the push plate inside the tube.
Control the Caulk Flow
Watch for excess caulk that may run quickly from the tube. If this happens, turn the pen and pull back on the plunger to release the pressure. If the caulk keeps running even with the pressure off, hold a rag over the tip and begin filling the crack as quickly as possible until the flow slows.
Fill the Crack with Caulk
Insert the tip into the crack starting at one end. Pull the gun along the crack so a bead of caulk just fills the space between the two surfaces. Caulk a few feet and release the pressure on the tube.
In some situations it may be easier to push the caulk gun along the crack rather than pulling it as illustrated here. We don't recommend the pushing method because it can be difficult to monitor the caulk flow, causing gaps in the bead. Recaulking to fill the missed spots can cause problems with excess caulk.
Smooth the Caulk
Wet an old cotton t–shirt or similar cloth and squeeze out the excess water. With your index finger inside the cloth, run over the caulk to smooth it out while pushing it deeper into the crack. Turn the cloth to a clean spot frequently to avoid a buildup of excess caulk. Finish the bead by wiping any caulk from the wall and trim surfaces. After the caulk is smooth be careful not to disturb it until it has time to set and cure.
Continue caulking a few feet at a time. Use the cloth to smooth each new run of caulk into the last. Rinse the cloth frequently to remove collected caulk and avoid spreading it to unwanted areas. Let the caulk set for an hour or more before painting. The bead will not be hard for about 24 hours so be careful not to disturb it with the tips of the brush bristles when cutting–in.
