Hi all,

There are always these little bubbles where I brushed on cortec (8 part cortec to 2 part water dilution), and no matter how much I brush the bubbles won't go away.  They dry into tiny little bumps that can be felt.  Has anyone else had this problem?  What is your solution?

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Yes, Cortec is not so happy going on with a brush. A foam brush works better than a bristle brush. Using about 1/4 isopropyl alcohol and 3/4 water helps. Making sure the surface is a little bit abraded and very clean (scotchbrite and isopropyl alcohol wipe) helps. Spraying instead of brushing is best. The cheap Harbor Freight HVLP detail gun, that holds about 1/2 pint, works fine.


Thanks for the advice!  I will give foam brush a shot.  Spraying would definitely be good, but I can't tolerate the smell and overspray.  When you say 1/4 alcohol and 3/4 water, do you mean that as the solution to go into the 8:2  dilution?  so 8 part cortec, 2 part of 1/4 alcohol and 3/4 water?

I am sensitive to paint vapors too but have been pleasantly surprised, no reaction from either Cortec or Stewart waterborne primer/topcoat, and using a small detail gun as I described means little overspray. Yes, I mean 4 parts of Cortec and 1 part of 25% alcohol, or 16 parts of Cortec, 3 parts water and 1 part 99% alcohol. The ratios are not critical. You want a *very thin* layer of Cortec.

I cut up strips of paint rollers about 3/4 wide by few inches long.

makes a great strip where you just need to be behind an l or something.

Also you can get a bunch of them from one roller and just throw them out or cut the used portion off

Ditto the foam brush. I bought a large quantity of cheap foam brushes and just tossed them when through! I never had problems with bubbles - thinned with distilled water to TLAR (That Looks About Right!)  ;>)

BTW, Caleb at Zenith said it was OK to mate surfaces even if the Cortec was still a little wet (although a thin film will dry pretty quickly!), but if doing so, be sure you're not planning to disassemble again as the Cortec makes a great glue! Don't ask me how I know!  :>(



Thanks for all the good ideas guys.  I went out and got some HD foam brushes and will water down the cortec nicely on my next go around.  Let's see if this makes for some better results.

Hi Ed, I'd appreciate a report after you made the adjustments! I've been following what you guys have been saying and would like to do the same. Thanks.

Will do!


The adjustment worked.  I didn't have any alcohol, but I did 4 part cortec to 1 part water and applied with home depot foam brush.  The results were excellent - the foam brush laid the cortec on nice and thin.  No bubbles, and drying time is up too with the new dilution.  

Big thanks to David and others that helped out with this one!

Yes, thank you Ed, and thanks to all!

OK, looking for the definitive answer. Wing kit is arriving soon and am switching from self-etching primer to Cortec. Mostly due to the curing time of the primer. Now, I've seen after searching to apply the Cortec straight, or diluted with thinner, or water, or alcohol. What is the best way to thin it? Also, once dry, is it paintable?


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