white UV stable caulk that tools well?


I'm looking for a good sealant that is white, UV stable and a bead can be nicely smoothed out. It's for around hose/electrical connections and clearance lights etc on a new build.(not on the roof) The camper is painted Aluminum.

I have been using 3m 4000, but that was to seal between two surfaces that are hidden, it doesn't seem to smooth out very well(im comparing to a wet finger with latex or silicon)
I've read good things about Sika 521 and Gocel proflex, I suspect there is no single answer.

Any ideas?


I was going to mention 3M4000, but was also going to say that I have never tried tooling it, because on boats all the bedding (caulking) compound goes under the flange of whatever is being bedded. Reason is that stuff on top doesn't do anything for the watertightness (either the under-flange bedding is good, or it isn't and needs to be re-done), so just attracts dirt and etc. Basically if you see tooled caulk on a boat around the outside of a port (window) or other fitting, you know it's leaking and someone has applied a stop-gap until they can re-bed it for real. And you can't get much more demanding than a boat that's pounding and twisting its way through bursts of green water for days on end.

Okay, that sounds really negative, but gets at something I've always wondered about on RV's: I see a lot of caulk on top of things and/or around the perimeter -- even from day 1 at the manufacturer. But I don't understand why (?)


I'm in building construction and maintenance and have used a lot of different products over the years.

3m 4000 gets chalky after 5 or 6 years and is too thin for vertical applications. I used it for years to patch membrane roofs but only use OSI Quad now.

OSI Quad is UV stable and a great adhesive, skins over in about a day, and shrinks like 17% as it cures. That means you can just do your best with the caulk tube and it'll make it 17% better on its own. The downside is that isn't particularly toolable, though I have had luck saturating a finger in Spray 9, misting the surface of the Quad with with spray 9, and wiping it around.

NP1 is similar in stick-to-you-ity as OSI. Siroflex is UV stable, toolable, and paintable, but stays sticky and adheres dirt. The Geocel stuff is weird and buttery. I can't remember the long-term specifics, but I think it stays sticky like Siroflex.

Your best bet is to find someone good with a caulk gun and to use OSI Quad. It comes in a huge variety of colors, including clear, stays flexible but not sticky, and is my favorite for most applications.


Thanks for the detailed reply, I will check out the OSI quad.
Sticky and retaining dirt is something I would like to avoid.

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I use OSI quad for nearly all my outdoor needs, seems to hold up the best of what i have used. It is a bit messy. best job is when i tape it.


I picked up a couple tubes of the white OSI Quad from the Depot, only $5 and change per tube, is this the right stuff? Seems good per the label, bonds to most anything.
Thanks again for the help

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