Black Mold on Fiberglass!

May 19, 2017
20
Catalina 27 Al Larson Marina San Pedro Ca.
What do I use/process to remove the black mold from fiberglass deck?
Thank you!
 
Feb 20, 2011
7,990
Island Packet 35 Tucson, AZ/San Carlos, MX
Some strong bleach should help, but I think the world's gone a little overboard with regards to mold. Black or otherwise.
 
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Aug 3, 2012
2,542
Performance Cruising Telstar 28 302 Watkins Glen
Magic Erasers work. 1200 grit wet sanding works. Scrub with Simple green and power wash works.
Afterward, try to seal the deck to keep the mildew out. Polishing the gelcoat first will help close the pores and keep the mildew out.
 
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Jan 24, 2017
666
Hunter 34 Toms River Nj
Try white vinegar and hydrogen peroxide 50/50 mix with a couple of drops of dish detergent. Works great on fabric and fiberglass.
 
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Aug 3, 2012
2,542
Performance Cruising Telstar 28 302 Watkins Glen
The issue with removing mildew is how to prevent the recurrence. Once the gel coat is porous, mildew will move in. You can polish the gel coat. I normally do that by polishing with wet sanding or compounding. You do not have to wax decks, but you can polish them. By polishing, you are removing a minute amount of material.
 
Mar 26, 2011
3,400
Corsair F-24 MK I Deale, MD
If it is mildew. If it is actually black algae or lichen, then BAC works better. Mildew doesn't really like to grow in the sun, so don't leap to conclusions based solely on appearances. These can look a lot alike. Mildew is what you find in dark places. The problem with bleach is that algae is a plant, and bleach doesn't kill plants efficiently. Same with lichens. The BAC will also impart some lasting protection.

https://www.practical-sailor.com/issues/37_57/features/Fighting-Mildew-Mold-and-Lichen_11798-1.html
 
Mar 26, 2011
3,400
Corsair F-24 MK I Deale, MD
Try white vinegar and hydrogen peroxide 50/50 mix with a couple of drops of dish detergent. Works great on fabric and fiberglass.
This is actually a reasonably dangerous practice, generating peracetic acid. This is NOT just vinegar and H2O2, this is much more reactive. OSHA has not yet established a safe exposure limit, but sub-PPM is expected. Read up on proper dilutions before proceeding. Certainly not something I would slop liberally around the deck without doing the reading. Sure, some folks get away with it. Some folks mix ammonia and bleach. But please, don't believe me, Google "peracetic acid."

A safer approach, if you like peroxide, would be to just use Oxiclean. Less aggressive, but MUCH safer.

And it is a myth that vinegar will keep mildew away if subject to rinsing. The pH rises and it just becomes food, growing mildew faster. Mildew likes a weak acid environment.
 
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May 19, 2017
20
Catalina 27 Al Larson Marina San Pedro Ca.
Thank you brothers for all the suggestions!
I'm trying to save a buck! I'm reading The Cruising Life by Jim Trefethen, good stuff!
Anyways the previous owner left a squirt bottle of bleach in the dock box, i'll try that in the morning, when my ship comes in I can buy some more chemicals.
 
Jan 25, 2011
2,391
S2 11.0A Anacortes, WA
With the boat stated in your info, and you say its on the deck, I'm assuming its in the nonskid? Take some soap and a good stiff deck brush (without handle) and scrub it out...Then, figure out why it appears. I had two areas on my boat. All my halyards go aft to the cockpit and they lay on the cabin top. All the lines soaked up water and mold started and migrated into the nonskid. I cleaned the lines (water and soap) and scrubbed the nonskid and the sun took care of the rest. Now I tie the halyards off the deck to the boom during winter months. I also had some mold in the very back of the cockpit sole. The binnacle cover goes down to within several inches of the sole creating a little micro climate. Still need to shorten that cover... no chemicals..
 
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Joe

.
Jun 1, 2004
7,999
Catalina 27 Mission Bay, San Diego
simple green or Zep cleaner and a stainless steel wire brush for the non skid...
 
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Feb 14, 2014
7,399
Hunter 430 Waveland, MS
I'm trying to save a buck!
Natures own fungicide and algaecide cleaner that is gentle on surfaces.
https://www.20muleteamlaundry.com

Borax...

Formula A:
This Part of Formula B in Gunni's link on post#8.
Jim...

PS: 1/2 cup of Borax per gallon, mop on, go drink 2 beers and rinse off. It will leave a bit of protection/prevention for a while.

PSS:Borax in a slightly different form is the remediation chemical for Toxic Black Mold.
 
Feb 26, 2004
22,760
Catalina 34 224 Maple Bay, BC, Canada
I'm trying to save a buck!
Don't be pound wise & penny foolish. You may be aware of the incorrect assumption that it takes twice as much to correct mistakes: NO! It takes three tines as much: One to do it wrong; Two to spend the time figuring out the mistake; Three to fix it and do it right which you shoulda done in the first place! Specifically, just like the input provided to you here, that using the wrong stuff is just like, uhm, wrong.
 
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