Mold cleaner recommendations for caulking

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PhilFishes

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Team Grady - I could use your advice. I have some black spots on the white caulking on by Grady. It looks like it could be mold, but when I've tried using a mold removal spray that I bought from West Marine, it didn't do much. Neither did standard "boat soap" products. What can I do to get rid of the black stuff? I've been hesitant to scrub too hard, as I don't want to damage the caulking. Thanks in advance for your recommendations!
 
The problem is that it's dug in deep. Try misting some water/bleach/a few drops of dish soap on it. Keep it moist. Let it set for a while. About 10:1 water:bleach is fine. Another option is to saturate paper towels with water:bleach and let that set for a while. Chances are it will work if left for long enough, but if not, your only other option is to cut out the caulk and replace.
 
You didn't mention how old the caulk is ( original to the hull year) but the caulks generally have a mildewcide that over time looses their potency. You may not be able to remove all of the stain.
Try the bleach as mentioned but apply it to the caulk and do not let it sit on the gel coats for extended periods.
 
I have found that 4200 gets mildew stains. Grady used it in a few spots...hardtop, pulpit...

I made the mistake of resealing one of the gunnels with 4200. Looks like crap now. Never comes back to white no matter what I do. Need to dig it out and replace with "window & door silicone"
 
Make a slurry of common powdered cleanser containing bleach (Comet etc) and slop it into the joint. Let it sit for a couple of days and keep it wet. Then rinse well.
 
SkunkBoat said:
I have found that 4200 gets mildew stains. Grady used it in a few spots...hardtop, pulpit...

I made the mistake of resealing one of the gunnels with 4200. Looks like crap now. Never comes back to white no matter what I do. Need to dig it out and replace with "window & door silicone"
Click to expand...
My local dealer, Seel’s uses “Almond” tinted silicone. Matches the factory color well.
 
Be careful mixing chemicals like chlorine bleach with other cleansers.
It's best not to mix any cleanser with another.
Coastboater said:
My local dealer, Seel’s uses “Almond” tinted silicone. Matches the factory color well.
Click to expand...
4200 and 5200 for that mater are adhesives that also seal but are not sealants. The adhesives are intended for parts that don't move with respect to the other parts they are attached to. For example, 4200 for a thru hull is fine but not for a locker lid that is subject to flexing or expansion/contraction.
As to the almond color silicone. Yes it matches fairly well but make sure you get one with the mildewcide that you typically get with a Kitchen and Bath product.
Also note that silicon is not intended for below the water line use.
 
Hookup1 said:
For me it yellows things. Also I hate them smell.
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Interesting. I've used this method for decades (around the boat and the house) on caulk, gelcoat, vinyl (not stitching) and have never had any issues.

To be clear - I'm not knocking anyone for the recommendation or the OP for trying something else. I was just curious.
 
Good info.
It took me a while to find the actual link to wherever this info was posted on the Grady site but eventually I found it
Go to the link and then click the page control to page 5.

Grady-White | Customer Tips

Learn about boat handling, seamanship, maintenance, fishing, dining and more in the Grady-White Customer Tips area.
www.gradywhite.com www.gradywhite.com


I always have Soft Scrub around with my boat cleaning supplies but I wasn't aware of applying it for a 24 hour duration.
 
That picture is exactly what I was talking about with the 4200 on the gunnels. In that spot, they are using 4200 for its adhesive properties.
It never really comes back to white/cream. There is always faint grey spots. After bleaching it will look ok for a while. (yes I use Softscrub and sunshine)
Silicone on the tank hatches will come clean and usually not get mildew at all, except the places where water puddles.

also, pet peave, the lids on Softscrub bottles are Bullshi!!!
 
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