# elastomeric cracking



## wncpainter (Aug 7, 2010)

have been using elastomeric 100% modified acrylic caulk for some time,, but lately its been cracking and aligatoring after a flat paint application,, does not seem to matter whether its two hours or two weeks before its painted nor depth of caulking, its still cracking after paint. Not happening with egg-shells or semis,, but only flats. Happened on two seperate indoor jobs and temp and humidity have been steady. any ideas or suggestions? any other top caulk choices.


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## ewingpainting.net (Jun 2, 2008)

Its because the flat paint is not compatible with the elasto caulking. You should prime the caulking 1st. The only thing you can put over elasto caulk without priming it is elasto paint.


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## Schmidt & Co. (Nov 6, 2008)

wncpainter said:


> any ideas or suggestions?


Maybe try a different caulk? :whistling2:


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## ParagonVA (Feb 3, 2009)

ewingpainting.net said:


> Its because the flat paint is not compatible with the elasto caulking. You should prime the caulking 1st. The only thing you can put over elasto caulk without priming it is elasto paint.


I'll vouch for this- it works. I've had problems as well with the flat paint shrinking/alligatoring on top of the caulking- almost as if it were going over silicone. I swipe the caulking real quick with a small brush loaded with a latex primer and that does the trick. The only flat paint I've seen that never cracked was Valspar believe it or not.


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## briancreary (Oct 12, 2010)

TowerTech all the way


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## wncpainter (Aug 7, 2010)

product specs indicate that its the "best paintable formula" yet you need to prime?? its always been bomb proof for me on exterior, but me thinks I need to find a new interior brand


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## briancreary (Oct 12, 2010)

Probably way different binders in exterior paints. UV protectants and a whole bunch of other stuff.


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## oldskool (Nov 17, 2009)

We are having the same issues, my theory was that a flexible caulking(what you want) with a flat (inflexible) paint over the top will eventually crack as the caulking moves and the paint doesn't . Hadn't thought of the in compatibility of the caulking and the flat paint.

Eggshells and semis won't crack because the film is much more flexible. if the caulking alligatores the flat because of incompatibility then eggshell and semi should too.


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## oldskool (Nov 17, 2009)

Tested gripper, 4 caulks and a high end flat. 

So far, over the four (dap 200, ici acrylic 45 yr, ici elast 55 yr and smart caulk)different caulks, I primed half then top coated with two coats of flat , then the other half only two coats of flat. Where the flat went over the primed caulking, there are noticeable cracks, where only flat is there are no cracks. I have 24 hours on the test and will monitor it over the next few days and weeks.


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## captainblando (Aug 8, 2010)

why exactly are you using elastomeric inside?


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