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Silicone Caulk

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By Tim Carter
©1993-2010 Tim Carter

Summary: Caulking can be a very messy job. Discover some tips on how to caulk a tub or shower. Knowing how to caulk will make your silicone caulk job look better and you will caulk smoother.

DEAR TIM: Caulking is not my favorite job. I have to use silicone caulk to seal a leaking shower enclosure. Can you offer any tips on caulk removal so I do not damage the metal or the marble curb? What is the secret when working with silicone caulk? I always end up with a mess. Beth S., Sarasota, FL

DEAR BETH: Silicone caulk is a fantastic product, but many will agree with you that it isn't user friendly. Not only can you get really irritated with the mess it creates, but also be very careful if you wear contact lenses. The fumes that are generated as the caulk cures can cause significant eye irritation. Be sure to read the safety label on the caulk tube before you use it.

I recently had to do a nearly identical job in a home I just purchased. The silicone caulk joint between a marble threshold and the aluminum shower enclosure had failed. To make matters worse, the tile setter placed the marble threshold so it had a reverse tilt. Water would pool against the aluminum frame instead of rolling back into the shower. This little bit of hydrostatic pressure caused the water to seep under the aluminum frame and soak the adjoining wall.

Installing silicone caulk can be tricky. Try to squeeze out the exact amount you need.  PHOTO CREDIT: Tim Carter
Installing silicone caulk can be tricky. Try to squeeze out the exact amount you need. PHOTO CREDIT: Tim Carter
Years ago I discovered that to successfully caulk tubs and showers, the joint that is to be caulked needs to be dry. I have a feeling the previous owner knew about this leak as it appeared the joint had been caulked multiple times but with little success. My suspicion is the repairs never worked as the silicone caulk they used was not able to make a good bond. Water was trapped under the aluminum frame and seeped out as the caulk was applied.

I was lucky and was able to use another shower in the house so the leaking one could dry for weeks. If you can't do this, then maybe think about getting ready to do the repair just before you go on vacation or out of town on business. As soon as you get back, install the silicone caulk on a dry joint.

Caulk removal can be tough. I have had great success using an old-fashioned straight-edged razor blade. In my case, I was able to hold the blade at a very low angle slicing between the old silicone caulk and the marble. This didn't cause any scratches. I then cut down through the old caulk with the blade as close to the aluminum frame as possible, but not touching it. The beads of old silicone caulk peeled off the shower like pulling up a strand of spaghetti from a plate. You will probably have the same luck.

I then used some rubbing alcohol to clean the marble and the aluminum frame making sure both surfaces were bone dry and clean. Caulk is really an adhesive, so it works best when surfaces are very clean.

Because I have caulked things for years, I knew how big to cut the tip of the new silicone-caulk tube. This is very important. Make the diameter of the hole no larger than one-sixteenth-inch wide. You do this by cutting the tip of the tube in small passes. It is easy to cut the hole too large.

To get professional results, you must squeeze the caulk from the tube slowly and evenly. A good caulk gun does this with ease. Inexpensive caulk guns will cause you nothing but headaches. A great caulk gun usually costs double or triple what a cheap one costs. It is the best money you will ever spend on a tool.

The secret trick I have used all these years is to apply just enough silicone caulk that when I immediately smooth it with my finger, no excess caulk oozes out around my finger onto the surfaces. Since we all have fingers that come in different sizes, you will need to experiment to determine how much caulk works with your finger.

My advice to you is to make a test corner using two scrap pieces of ceramic tile. Glue them to the inside of a low cardboard box. Start practicing on these mockups until you master the technique. It is not as hard as you might think. I like to caulk a strip about 2-feet long before wiping it with my finger. Be sure to have paper towels on hand to clean up any accidents.

Another secret tip when working with silicone caulk is to wear old clothes and work in a well-ventilated space. The fumes generated by the curing silicone caulk are very strong. If you get silicone caulk on clothing, it is nearly impossible to remove it from the fibers.

You can absolutely get professional results if you take some time and practice. Be sure to take your time applying a smooth bead of silicone caulk, not one that has blobs and voids. When your finger hits a blob of caulk, there is no doubt some will ooze out onto the marble and aluminum creating a massive mess.

Remember that the caulk needs to fully cure before you use your shower again. Don't be fooled thinking the silicone caulk is dry just because it may be tack free within an hour. To fully cure, it needs to react with water vapor in the air. In dry climates, it can take two or three days for your new silicone caulk to fully cure.





Comments:

Paul Burke
04 Sep 2008, 01:47
Hi Tim,
You mention about smoothing the silicone with your finger. Do you mean your bare finger, or with soapy water, or a rubber glove??? Keep up the good work. Paul Burke
Graham Green
04 Sep 2008, 04:29
Here's 2 cents worth: use a sealant that contains a mould inhibitor. Ultimately the inhibitor will leach out of the seal and therefore stop working but even in heavy use areas it will be good for a few years.
For some reason silicone with inhibitor is EVEN more fussy about damp conditions than regular silicone everything has to be dryer than a nun's naughty bits.
Invest in some spare nozzles and a smoothing kit.
Several manufacturers sell silicone sealant dissolver if you really get stuck but it costs more than the sealant.
Richard Zapor
08 Sep 2008, 02:54
I've been a handyman /contractor for 35 years .I pretty much gave up on silicone caulk several years ago for most applications because it is so hard to work with. And there are much easier products to apply that work as well or better than silione .Recently I have seen a couple of new caulks out that advertise that a tub/shower can be used within 2 or 3 hours after being caulked . These caulks seem to be non-paintable silicones that are as difficult to apply as traditional silicones but do get around the problem of a long wait for the homeowner to be able to use a recently caulked tub/shower.
I do agree with the application methods you suggest for silicone caulk . My rule of thumb for caulking in general is to try to apply caulk with the gun the best I can and as if I were not going to "finger it out" after gunning it on . But in most cases I am going to finger it out , but the better it is gunned on the easier it is to make best end result with my finger . Cutting of the tube tip with a small hole and a diagonal cut followed by a cut perpendicular to the axis of the tube just at the very tip are essential, as is putting on a small amount of caulk that won't ooze out around your finger. With latex caulk I use a wet rag to wet and wipe my finger between strokes and usualy a bucket of warm water to keep washing it out .On my first painting job 35 years ago an old timer told me " the caulk just goes in the crack not all around it too ". Its way easier to add a little more caulk if needed than to clean up a mess of it cause too much was put on to start with.
And I have found a patented caulking gun that really does not let the caulk ooze out of the tip after you have stopped applying it and without my having to do anything except stop squeezing the trigger. Ureka !
Happy caulking from Richard's Finestkind Services in Columbus Ohio !
Graham Green
08 Sep 2008, 06:27
I agree with Richard on the new generation of caulk guns and not putting on more than is needed but one of the points I was making is that for a few dollars the plastic smoothing tools do a good job.
Nine times out of ten you do want to cover the edge (at least one if not both) of the adjoining surfaces and not just fill the gap.
You should take my comments with a pinch of salt though because I'm a cook and it's just more icing to me.
All the best. g2
Alan Barabash
02 Oct 2008, 18:37
I've found that putting a strip of 3/4" masking tape about 1/4" away from the line to be caulked on both sides works. When you run a wet finger along the caulk it makes a neat job. Also the line of caulk is straight on both sides when the tape is removed. This method is for people ,like me, who make a mess when caulking.
MF
30 Nov 2008, 20:47
I recently installed a bunch of windows and used a low VOC silicone caulk. Compaired to previous experiences with silicone, this stuff was awsome. absolutely no odors at all.
Allen
05 Dec 2008, 19:02
I also use tape (blue painters tape or electrical tape around curvy sinks and such), leaving about 1/8" on either side of the caulk line. This keeps the mess to a minimum and makes nice straight lines.

Also, dip the finger in water water based caulk and in rubbing alcohol for silicone caulk when smoothing for good results. You can tape up a paper towel to the wall to give you about 30 wipes on one towel.
Rob Rhindress
21 Dec 2008, 16:58
Hi Tim,
I live in the northeast and would like to know if there is a caulk that can be applied to windows in cold temperatures.
Keep up the great work!
Rob Rhindress
A.G. Farah
10 Jan 2009, 21:15
When using painter's tape to line off the edge on a long run, when is the best time to remove it ? When I remove too soon, it tends to ripple the edge of the caulking and I want to get a perfect edge.
Les Bussing
11 Jan 2009, 14:26
I recently put up some backerboard in my folks bathtub area and caulked it with a 100% silicone product for kitchen and baths. At first, the caulk came out of the tube clear but by the time I got to about 3/4 of the tube gone, it started coming out milky color. The caulking has been curing for about 5 days and has never cured. It is still real gooy and sticky to the touch. I have heard about glycerine and moisture to help the stuff cure. Do you have any suggestions?

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