Bottom Line

 Use GE Silicone II if it's in the tub or shower, or if it doesn't need to be painted. 

Use DAP DYNAFLEX 230 Premium if it has to be painted.


The general issues in selecting a caulk are:

  • Silicone or urethane usually perform best overall. They last longest and hold up best, but are harder to apply (can make a real mess) and silicone isn't paintable.  Silicone "Tub and Tile" caulk has a mildewcide -- use in areas that get wet, but don't use it in an area where it will contact food or drinking water.  There are other versions without the mildewcide for these applications.   [A possible exception to silicone being the best caulk is urethane caulk which may be as good and is paintable.  See discussion below.]
  • Elastomeric latex sealant (caulk) comes next in durability and is paintable.
  • Latex, silicone/latex (siliconized) and acrylic is next,  but there's a lot of variation in quality within and between brands.
  • Latex is easiest to apply and cleanup.
  • Butyl rubber is dead last.

Silicone is essential to seal around bathtubs, showers, lavatories, etc. There's a special bathroom formulation for this that has a mildewcide. This poison has been known to be hazardous if used inside dishwashers because the high heat outgasses the poison onto the dishes and is then eaten.

Note:   If silicone does not cure it makes a godawful mess.  Most manufacturers specify a shelf life of 1-year from date of manufacturer for silicone caulk in unopened tubes.  I've not seen times for partially used tubes.  Silicone will last longer than a year, but if it's old you must test it to see if it is going to cure.  Silicone does not air dry, it has a curing agent.   If a sample placed on a non-porous surface does not cure to a resilient rubbery consistency in 24 hours don't use it.

THAT well known consumer product rating magazine last rated caulk a while back. Here's what their tests showed then:

  • You can't judge anything by brand. Every brand had caulks that scored throughout the range from good to bad.
  • The best silicone caulks were GE Silicone II and Ace 50 Year Silicone, with Red Devil 100% Silicone next. GE Silicone II comes in 2 types -- one with mildewside for 'Kitchen & Bath' and one without for 'Windows & Doors'
  • DAP DYNAFLEX 230 Premium  previously called DYNAFLEX 230 and before that Formula '230' is the best latex.Note1  It's an elastomeric latex sealant.  It's more expensive but, it's better than all silicone-latex caulks and better than some pure silicones. I use this caulk where silicone isn't appropriate . It shrinks a lot. I recommend you don't use the clear version unless you have to.  The clear has an additive to make it go on white so it's easy to see if you're covering cracks.  It turns clear as it cures.  This causes it to shrink A LOT and it can't be painted for a week!  The regular colors shrink less and can be painted in a couple of hours.
  • NOTE 1:  I used and recommended DAP Dynaflex 230 caulk for years.  Then, I had to face the fact that there's a serious problem with this caulk.  It appeared to be one of the worlds best nutrients for mildew.   I made this page to illustrate the problem I've had with it. They now have a product named DYNAFLEX 230 Premium which appears to be DYNAFLEX with mildew resistance.  If so, it will be the solution, but I've never used it. 

The 2 worst other than butyl caulks were:

.....Ace 25 Year Siliconized
.. ...Seamseal Plus Silicon/Latex

Remember, you just can't judge by brand--two of the top rated and two of the worst rated caulks are from the same brands--Ace and DAP?

The PBS program "Ask This Old House" uses a Tripolymer Sealant a construction sealant by Geocel named 2300.  I've never used it but if they use it it's probably good.  It can be applied underwater, and to greasy surfaces.  You may have to get it at a roofing supply or lumber yard. 

Some  people on swear by a caulk named Polyseamseal adhesive/sealent (another elastomeric)  They're particularly high on this version for caulking tub/showers..  Unfortunately it wasn't rated, and I've rarely seen this product on store shelves. 

Urethane Caulk

Polyurethane caulk is growing in popularity.  NP 1 by BASF/Sonneborn has won high praise from Texas A&M for durability, and it's paintable.  But, it's harder to apply neatly than latex and, clean up requires solvents. I've been told there's a wide range in the quality in urethane caulks and I've had not experience nor seen ratings in these other names of urethane caulks -- PL200 or Vulkem, GE makes one, and recently I saw an expensive ($8) tube of urethane from 3M on the caulk shelf at Home Despot.

"Bruce Brocka" writes:

I was reading your section on caulks.  I have used everything and the best caulk by an order of magnitude is the NP-1 series by Sonneborn.  It comes in numerous colors.  It is wonderful, and can be painted or left alone. . . . NP1 was developed as a masonry caulk

Notes:  1)  I've found NP 1 difficult to gun (hard to push out of the tube).  2)  It takes a long time to cure (dry).  Expect to wait two to three days before painting.  (I now see the instructions say to wait until it is fully cured, which they say will take a week)  3)  Sonneborn limits distribution of NP1 to outlets that normally sell to the construction trade, such as roofing supplies, real lumber yards, etc., saying it's not for use by the ordinary consumer.  I get it at a local roofing supply company.   

For all this trouble I sure hope it's good  -- jim


Tip1:  Cold caulk can get stiff and hard to squeeze out of the tube.  If it's cold, put the tube it in a pan of warm water for 20 minutes or so.

Tips2:  Here are some ways to reseal partially used caulk tubes.

In the past I used a large nail stuck into the tip.  This works good for keeping the tip clear, but the nail sometimes rusts causing you to have to pump out a lot of caulk to get rid of the rust.  

Next I used a large wirenut (used to connect electric wiring) to cap the tip if I'd be using it again within a month.  The gray wirenuts are about the right size. 

Now I mainly use a piece of plastic (Saran Wrap or thin plastic food storage bag) over the tip, held in place with tightly wrapped masking tape or a rubber band (Click here for picture).  Squirt a little caulk into this "sock" covering the tip -- it will harden first, helping seal the caulk in the tube.  Some people use a piece of duck tape instead of the plastic wrap but it doesn't seem to me like it would be airtight enough.

Alonso Llano writes:
"I use a screw to seal my tubes of caulking, it's very inexpensive (actually free) and works all the time."  
NOTE:  You may want to use a rust proof screw.   Some folks use pliers to pull the screw out, claiming this pulls any hardened caulk out with it. -- jim

Brian writes:
"Instead of regular duct tape, use the metal-type duct tape.  I take about a 2.5 inch strip, wrap it around the tip with about one inch extended past the tip, then press the two sides of the tape together and fold it over the tip.  Works great.  For very long term storage I also two strips of the same-type tape to cover the open end of the tube -- yes, gases do slowly escape from there too."

These Little Red Caps sound like a clever way to reseal tubes of caulk, but I've never used them.  If you've used one on a tube that remained unused for as much as 3 months, please let me know whether it kept the caulk nozzle from clogging.  If you're going to store it for more than a week I'd squirt a daub of caulk into the rubber sock.

Some people say they have good luck with DAP Caps.  I've never used one, but they seem to be a cap for open tubes as well as a caulk troweling tool.  I use my finger for troweling and have never had good luck using a tool to trowel caulk, but I've seen TV handymen suggest using them so others must have a different experience with them than I have.

Recaulking a Shower or, a Tub-Tile Joint -- Getting a good seal is harder than you think.

Here's an article on caulking your home for energy saving.

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