Cleaning/prep before re-caulking?

[Mel R]

I've reviewed many posts about re-caulking and haven't come across this, so sorry if it's been answered already!

After we scrape off the old stuff, is there anything anyone uses or recommends for further cleaning/prep, before putting on new stuff?

[Joe Z]

After all the silicone is off I use clear rubbing alcohol to get all the old wax and dirt off for better adhesion.
Joe

[Frederick L. Simson]

I use clear rubbing alcohol

What Joe said.

[peterh]

Rubbing alcohol works fine for butyl tape, just let the surfaces dry thouroughly, but you may want a much deeper clean if you're using some other adhesive or caulk. Some marine adhesives warn you not to use alcohol, so check the packaging to see if they have recommendations.

[Capt Ron]

The solvent used should match whatever material is being removed considering the material it's being removed from. Fortunately fiberglass and epoxy once cured, are pretty much solvent proof so match the solvent with whatever you need to remove.

Some tape adhesive residues will yield to alcohol, some won't. Other residues sometimes will dissolve with mineral spirits. For removing old decals and stickers, I've had good luck with oven cleaner. Most cured caulking, silicone sealant and polysulfide are pretty much solvent proof like cured fiberglass and epoxy. For cleaning up fiberglass, usually strong solvents such as m.e.k. or acetone are used. Rust stains in fiberglass usually will dissolve with oxalic acid based rust remover solutions such as those sold by Home Depot or the dry oxalic acid in Bar Keeper's Friend plus a little elbow grease.

To remove old caulk from fiberglass, first mechanically and thoroughly remove the old stuff; Scrapping, sanding, hammer and chisel, whatever works. Then a good wet wipe down with acetone, changing rags often. Just don't let the acetone touch painted surfaces or foam or plastic.

By the way, urethane foams dissolve in acetone. This feature can be handy as temporary molds could be made of foam, the silicone or fiberglass parts cast, and then the mold dissolved away with acetone. Kind of a 'lost wax' molding method with chemistry.

[Joe Z]

Capt Ron
I've also used Acetone with no problems but was reluctant to give that advice because i wasn't 100% sure if it would hurt anything on a new trailer.... glad you had experience with it.
You also gave some other good cures that i have to try out
Joe

[Andrew Gibbens]

Wiping acetone on either gel coat resin or the laminate behind it is an industry-standard way of getting the surface clean before laminating more fiberglass onto it. It will do absolutely no harm for short periods - say, tens of seconds. If left on the resin for 5 minutes or more, it will start to permanently soften the resin and make it tacky: so wipe on and wipe off, not soak.

Andrew

[Joe Z]

thanks andrew....that's good to know.
Joe

[pjanits]

Acetone is nasty stuff for your body, wear gloves that won't be eaten by it.
Also the five minute rule may not apply as whenever I worked with the stuff it evaporated way faster than that, but there may some residue for sure.

Ventilate well or you will be higher than a kite in no time.