black mold spots on white silicone

TI

TinCocodrie

Member
Joined
Oct 13, 2008
Posts
19
Location
Cocodrie, La-- fishing camp
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.
 
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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
 
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.
 
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I don't know if this has been tried before to control mold, but I stumbled onto it while lubricating slides and metal joints on my TM.

I sprayed too much WD-40 on the runners for the stone guards over the rear window, and noticed that the runoff had gotten down to the caulk across the bottom of the shell. When I wiped the WD-40 off, the mold came off to.

I went around the entire trailer spraying WD-40 onto a papertowel and wiping the silicone caulk. All but the heaviest concentratiions of mold came off. Scrubbing with toothbrush lessened the coverage of the remaining mold. I will try fuuture applications to see if it will continue to work.

After wiping all of the caulk that I could reach, I went over those same areas with spray auto detailing spray. I doubt that the WD-40 caused any damage to the caulk. Only time will tell.

If you are adventurous, maybe give it a try. Let me know you thoughts about this experiment.
 
I would be leery about using standard bathroom caulk on the TM exterior. It may not have the UV resistance that a high quality silicone caulk has.
You may have to seek out an industrial distributor (vs Home Depot), but I would recommend looking into using Dow Corning 786 Mildew Resistant Sealant.
It not only has the mildew resistance, but it's an industrial duty SILICONE sealant which will give you good UV resistance. It ain't cheap at about $10 a cartridge, but somethings are worth the extra bucks in the long run.
 
harveyrv said:
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.
Click to expand...
This is great info, not only for caulking the TM but for redoing a bath! Thanks lots! Regardless of what I am reading about on this forum, I always learn something new and interesting!
Karen
 
OH, and forgot to mention, I use peroxide in place of bleach when I don't want the bleachy smell. Don't know if it works on mold/mildew but I use it diluted with water half and half for cleaning and disinfecting, especially vegetables from the store.
Just my two cents worth!

Karen
 
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