black mold spots on white silicone

[TinCocodrie]

2009 3023 stored outside in south Louisiana over winter
have developed black spots on all white silicone sealer on roof
have tried straight bleach, soft scrub with bleach, vinegar and baking soda, etc and spots still there
any ideas from the group?
lime away?
I'm sure I'm not the first one with this problem

thks
Terry

I had a product from an RV store, pump spray bottle that worked. I have also used Magic Eraser on some spots.
Sorry but I don't have the name as I used up the bottle.

There are some kitchen and bath mold and mildew products but I would make sure it did not effect the paint.

Nothing really works on this kind of mildew. The only thing you can do is replace the calk. Question is whether there's other caulk out there that won't be susceptible to mildew growth. I suspect that the manufacturers would be using it if there were such a think.

If it's really bad, there is a product that you can paint over caulk to make it white again. I think it was designed for grout originally. Not sure it will stand up to weather. You could try painting it with bleach but you might affect it's composition and if you spill it, it might do more harm than good.

Phil

A clorox bleach pen will work if you can find one. It has a fine tip so you can apply it to the caulk only. It will take a while to work but it will bleach out and kill the mold etc. I haven't used it in this application and it's pretty strong so I'm not sure if it will damage the finish on the camper if you miss.

There is silicone available with mildewcide in it, but manufacturers don't use it I suspect due to the potential chemical exposures for their employees, above that of the silicone itself.

If portions get really bad, you can remove it and replace with the product mentioned above. But there is not much you can do about it, and don't use bathroom products for mildew removal, many of them will attack silicone and say so on the label.

This is a wild shot in the dark, but you might try some OFF mosquito spray. Spray the mold spots in concentration, let sit a few minutes and wipe with a rough cloth. OFF works great as a stain remover on clothing and hard to get off scuff marks on flooring....but like I said its a wild shot, but might be worth a try.

I keep a sailboat on a warm, dirty and extremely fertile lake in central Illinois - the waterline scum that builds up is as tough and nasty as anything I might find on the TM. While I have tried bleach and products specifically designed to remove waterline stains, I've had my best success with "The Works" tile and bathroom cleaner which seems to be available at most local grocery stores. I suspect it would work on mildew but you might try it first on a small area to make sure it gets along with silicone. (As a bathroom cleaner it should.) - camp2canoe

Tin:

I live in Baton Rouge - my 2009.5 3023 is garage kept and has the same problem. I've found nothing to remove the black mold from the white caulk around the roof vents. If you find something that works, please let me know via post reply.

Thanks,

Skeetman

[Wavery]

The issue that you are experiencing with this type of mold is not growth of mold on the surface of the caulk. If it was, bleach would absolutely kill it and make it disappear like magic.

The problem is that the caulking was applied on a humid day and the mold spores embedded themselves in or under the caulking. Once the caulking has cured, the mold is allowed to grow inside a protected shell. No amount of chemical of any kind will penetrate through to the mold. If it does, the caulking would also be removed.

I would live with it until a very dry hot period. Remove all the old caulking and wipe the surface with acetone (acetone will disperse moisture) to remove any residual moisture (be very careful to get out any moisture under the moldings). Then lay down a new bead of caulk.

We don't have this problem on our campers in SoCal but we do in the calking in the bathrooms, if the moisture is not properly removed before installing the caulking. I manage a 40-unit apartment building and have 80 bathrooms that I deal with. I used to hire others to do all the maintenance. After years of problems, I do it all myself now. It took me several years of struggling with this issue of mold in the caulking before I figured out the real issue. Dap, makes a caulk that is advertised as "Mold resistant", I tried it with the same results. For the last 6 or 7 years, I have wiped down the joint with Acetone and the mold has never reappeared in those bathrooms.

Harvey:

Makes sense to me.

Thanks,

Skeetman