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I have patch a couple of places at the base of my shower with silicone rubber sealant using a caulking gun and it's worked well and water no longer escapes from the shower. However, where I have done the patching it is lumpy but where the original sealant is there is a smooth continuous finish.

Two questions:
1. Can the existing lumpiness (now dry) be made to look smooth?
2. What should I have done to make the finish look smooth and professional?

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See also: diy.stackexchange.com/questions/35/… – BMitch Jun 11 '12 at 17:12

13 Answers 13

up vote 29 down vote accepted
  1. You will have to remove it and reapply.

  2. The trick is soap. Have a bowl of water and a bar of soap. Dip your finger in the water then rub it on the soap before using it to smoothe the silicone.

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+1 for the soap idea. I've long used the "wet finger" technique, but don't like the mess left on the finger, and am hoping the soap will make that easier to deal with. I'm also thinking perhaps a wet bar of soap itself -- with rounded corner -- might substitute for the finger? – Jan Steinman Jun 13 '12 at 18:32
Silicon and latex caulks are different. With latex often just a wet finger is enough. – Bryce Sep 5 '12 at 7:53
Couple the soapy water with disposable latex-free gloves, and you get a smooth bead with easy clean-up. – Jeremy W. Sherman Sep 19 '12 at 1:49
Whoa...soap! Never thought of adding that to the mix to avoid the stuff sticking to the fingers. – DA01 Dec 3 '13 at 1:04

Definitely use a damp finger, and have a paper towel ready to wipe off your finger if you used too much caulk. Also, with silicone and difficult to clean surfaces, you want to tape both sides of your caulk line first. Remove the tape immediately after using your finger. This isn't needed on trim/painted walls since the caulk will disappear under the paint. But for places where you need a nice edge on the caulk line this makes a big difference.

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Not all silicone caulks are paintable. – Vebjorn Ljosa Jun 12 '12 at 8:52
@VebjornLjosa That's an important point that I probably wasn't very clear on. Thanks. – BMitch Jun 12 '12 at 10:13
I recommend against painter's tape. When you remove it after smoothing, you leave these nice mini-ledges at the edge of your bead that just beg you to pick at them, till all your dry caulk comes peeling off. – Jeremy W. Sherman Sep 19 '12 at 1:49
@JeremyW.Sherman The problem with not using the tape is that on some surfaces or some caulks (like unpaintable silicone), once it goes to the wrong place, it's not easy to fix. Worse than a ridge is a bunch of pealing paint or a crooked white streak of caulk in a porous tile. – BMitch Sep 19 '12 at 11:29
I've had success with taping. After I removed the tape, I made one more pass with my finger to lay the ridges down. The line stays fairly crisp because the excess was removed with the first pass. – Josh Bush May 13 '13 at 2:54

There's nothing you can do now other than remove it and re-apply. The pro's often just use their finger to smooth it out.

For those of us who don't have the magical touch, they make tools that allow you to put a nice finish on. There are a variety of different tools - this is just the first one that came up in a search.

Caulk Packer Tool

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+1 for the finger – BMitch Jun 11 '12 at 17:07

The cheapest tool you can get for the job is a Popsicle stick, which has a perfect end for a smooth finish. First of all, apply your silicone bead, then get a spray bottle with water and washing up liquid solution. Spray your bead sparingly and also spray your Popsicle stick then run it along the bead wiping any excess on a cloth as you go. At the end you'll have a perfect finish.

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The best way is to use glass cleaner spray on your hands. It stops the silicone sicking to your hands so you can get a smooth finish. It also gives the silicone a nice shine when dried.

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Just want to add:I used to use saliva on my finger,like a lot of people,but recently found out that the bacteria in your saliva starts the mold and discolouration,making the nice white bead around showers and sinks going black and moldy in no time(soaps water and two or three passes will get a neat clean job.)

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Use an empty tube from your silicone, give it a spray inside so it doesn't stick to the inner tube so it doesn't pile up, squeeze the end of the tube to desired width of the seal and run it along it, best tip I can give amateurs, popstickle sticks leave to much of a mess

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  1. Remove existing silicon, with a suitable scraper tool, knife or spatula. Clean the area with methylated spirits, bleach or your preferred cleaner. The idea is to kill any mould or similar under the silicon before applying.
  2. Use a suitable silicon product, e.g with mould inhibitors for bathroom/kitchens. Cut the sealant tube tip so the bead is wide enough to apply enough silicon for the area. It's better to have a bit too much than too little.
  3. Lay the silicon bead along the line with a caulking gun.
  4. Spray onto the silicon line with soapy water from a spritzer bottle. This stops the silicon sticking and makes it more pliable when finishing it. It also kills any bacteria on the surface, preventing it getting into the silicon.
  5. Use these amazing "Sealant edges" for a perfect finish. Reusable sealant edges

  6. There's different corner sizes from 0mm, 2mm, 3mm, 4mm, 5mm, 6mm, 8mm, 10mm, 14mm to 20mm to match the job. Scrape off the excess sealant, discard with tissues or disposable cloth.

  7. Leave to cure 24 hours minimum for a perfect finish!
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I do this for a living and it makes me laugh to hear what some people say is the best method. Use your finger...yeah right! Unless you use a special paintable silicone, paint wont cover it. Not all caulking compounds are the same. Now the simple method is apply silicone bead, spray with diluted detergent and then finish off on horizontal and vertical edges with a popstick. Flick the scraped off bits into a pot of dilute detergent solution. Change the popstick when edges become worn to keep a good finish. Run detergent moistened finger over the bead lightly after scraping off with popstick to prove the seal.

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Oh yes the painters edge tools are good for wider gaps and I use those as well but they can damage bead if you dont use enough detergent as they scrape off the detergent so if you have another run the tool will start to scrape out the silicone. Spray again. – How Much Can A Koala Bear Sep 11 '15 at 12:04

I agree with Josh. Going around the bath and inside the shower cubicle I tape up and as soon as I lay the sealant I get a tea spoon and scrape-off. When that is done I use wet soapy finger and quickly run round, this also gets rid of each bump as the spoon passes the grout line. As soon as I have done that the tape comes off immediately. Soapy finger again and one last run around just to take the little edge off. Had only praise from customers so far on a neat job. The tea spoons have different radius arcs on the tip so find the one with the most suitable arc for the gap from tape edge to opposing tape edge. I did see on the Tinterweb a tube video about using WD40 to lightly spray on the bead of sealant which looked a bit messy but I may try that at some stage (On my own tiles of course).

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Rubbing alcohol in a spray bottle. Spritz entire joint after running a bead down.soapy water on the flanges and seat the bead perfectly in one continuous motion. Takes practice.

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Soapy fingers work well. A slice of potato also does a great job and does not spread the silicone as much as a finger.

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Goof off works excellent when you put it on your finger and wipe the silcone bead clean.

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Not such a great idea: the MSDS for Goof Off Caulk Remover says that it's a "Skin irritant. Symptoms may include redness, itching, drying of skin." – Niall C. Oct 12 '14 at 23:37

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