How to Caulk

How to Caulk



There are three uses for caulk that come to mind.  One is for weatherization of your home.  Caulking around doors, windows, etc. will help to minimize the convective loss of heat and (the reverse) the infiltration of the cold air from the outside when the wind gets stiff.  Another use for caulk is as a sealant to keep water from infiltrating where it is unwanted and likely to do damage -around your bathtub /tile joints, for example.  Sometimes caulking is used merely for aesthetic purposes, such as by a painter, to fill cracks or joints in wood work before applying a protective coating (paint or other sealer). 

Be sure to consult a subject matter expert about which type of caulk to use for your application.  Considerations are: location, temperature, humidity, moisture, whether movement is expected in the joint material (how much flexibility is required), interior or exterior application.

The term caulking was originally a boat building term.  The term sealant is used for weatherization.  Mostly, the two terms are interchangeable today.



Home and Garden Tip: Get a ‘No-Drip’ caulking gun.  After you stop squeezing the handle, the material will cease to flow.  There are three (3) types of caulk -as with most things, cheap, middle of the road and higher end.  The prices range from about $1.50 to $5.00.  The low end stuff isn’t bad, necessarily.  It has a higher water content and is a little more difficult to work with if you are not familiar with it.  Caulk is water soluble.  A caulk has to be able to expand and contract without compromising the seal.  The higher end stuff contains less water and is better suited for filling wider gaps.  The caulk you lay out will shrink 3-5% as it sets-up (dries).



Trim the tube nozzle at a 45 degree angle with a sharp blade, being careful to keep your fingers out of the line of fire.  Cautionary Note: Gloves (as PPE) are always a good idea when using sharp blades. Be careful not to cut the nozzle so the opening is too large.   It is better to cut it small and cut it again if needed.  Then shave down the sides of the nozzle so the dimension is uniform on all sides.

Hold the caulking gun at a 45 degree angle to apply a bead of caulk to the joint you are about to seal.  Run your wet finger down (or across) the bead to smooth it out.  Always have a bucket of water with a clean rag to clean your finger and any spillage or smears.  The sealant should flow like a wave (ahead) in front of your finger without emerging (oozing) from the left or right side of your finger.  If it does, you have laid out too heavy of a bead.  For that possibility, only lay out about a couple feet at a time.  Once you are well practiced you can expand on that.

When caulking exterior surfaces -do not use clear caulk.  Clear caulk will attract and collect pollen and dust and will eventually turn brown. It is best to caulk using white or any other color and paint over it.  Item of note:  When you do use clear caulking -it will be white when applied and be clear when dry.

When caulking outside, be cognizant of the temperature and humidity -to be able to be able to judge how long a bead you can lay down and be able to work it in before it begins to dry up too much.  The surface of the house may be considerably hotter than the ambient temperature.  Caulk on a hot surface begins to evaporate rapidly.

Once it begins to dry, if you don’t have it right, you lost your chance to smooth it out, possibly requiring removal and rework.  The technique of running your finger down (or, across) the bead at a 45 degree angle and not having so much caulk on there that the material oozes out from the sides of your finger is sound technique.  Except for the fact that the skin on your finger will wear down rapidly and be of no use until it heals.

Your finger is adequate when caulking a bathtub or shower. If your job consists of hundreds of feet of caulking, your finger isn’t the right tool for the job.  Gloves won’t work.  Rubber gloves will wear out quickly.  Instead, cut a clean cotton rag into 4″ square pieces.  Soak one with water and use it pulled tightly over your finger.  Rinse it often in the bucket and it will give you the same smooth finish your bare finger will -with sacrificing your fingerprint.

More info:


How to Save Energy

Weatherization Programs

Tighten Up Your Home

Caulking Teak Decks on Boats

Sikaflex Description and Review

Silicone SealantsA Reference

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