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Old 12-30-2013
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Blotches on deck - can you identify

I recently acquired an 1989 Catalina. Since buying it, I had the deck and hull waxed, and have washed it down several times. Earlier this week after a rain shower the blotches and stains appeared. Some were pinkish others were gray/black. I hosed them down but they persisted. Next day they were gone. Can anyone help me with this mystery?
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Last edited by armandolio; 12-30-2013 at 10:59 PM.
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Old 12-30-2013
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Re: Blotches on deck - can you identify

I have the same thing on my boat. Im currently in SE Florida awaiting the Xmas trade winds to die down a bit before proceeding further south.

My speculation/guess is that this is airborne bacteria, probably coming from Africa, and is using the wax on boats as its nutrient source, as unwaxed boats dont seem to have the problem. Also interesting was that this 'blush' when off central and northern Florida (NE trade winds) was 'reddish', in SE Florida (easterlies and southeasterlies) its more greyish. If it was dust from the Sahara it would be more 'yellowish', so my guess its probably bacteria as its quickly removed (bleached) by a wash with diluted oxalic acid solution. The recent sunrises and sunsets here have also been 'brilliantly yellow' which is unusual.
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Re: Blotches on deck - can you identify

RichH,
Interesting theory. That never occurred to me.
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Old 12-31-2013
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Re: Blotches on deck - can you identify

Are the blotches in areas where people with bare legs have sat? Might be the chemicals from sunscreen.
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Old 12-31-2013
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Re: Blotches on deck - can you identify

You had the boat waxed? Deck and wax doesn't go well together:
1) difficult to clean as the anti-slip on the deck works against cleaning. Not to speak about removing old oxide and even the surface with rubbing etc, this is just not possible if one wants the anti-slip to remain.
=> deck surface will not be really cleaned.
2) wax makes the surface more slippery (there are special anti-slip waxes, but in my experience they are not good in any respect).
3) decks are usually horisontal. Moisture and dirt doesn't just drip away, but stays longer, some of it forever it seems.

The blotches you see can be any kind of dirt that was not really removed before waxing, combined with water / moisture. Can also mainly be just increased moisture in the wax. Disappears when the surface has dried. Comes back when new water is applied.

If you can't live with it (I would) then you have to completely remove the wax. Then you have to decide if you want new wax or not.

An alterntive solution is to paint the deck. Up-side is that there is no wax, no such issues - and you get a fresh deck in the color you prefer. Downside is that the deck need to be repainted now and then.

/J
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Re: Blotches on deck - can you identify

I misspoke. The waxing was of the hull and cabin top, the horizontal parts.

Jaramaz - while your explanation of it being dirt exposed by moisture makes sense, the mystery remains. It was not exposed during washing of the boat, only after it rained. Then they disappeared.
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Old 12-31-2013
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Re: Blotches on deck - can you identify

looks like you polished thru the gelcoat to almost fiberglass...stop polishing. prep f or paint or gelcoating, which is prohibitively priced. is why folks paint their old fg boats.
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Re: Blotches on deck - can you identify

Are you by any chance downwind of a boatyard? Sanding dust from copper bottom paint turns decks funny colors after exposure to moisture from rain or dew.

BTW, the best (and cheapest) product for removing stains from gelcoat that I have ever tried is Lysol toilet bowl cleaner in the squeeze bottle. Be very careful around aluminum though.
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Re: Blotches on deck - can you identify

No boatyard anywhere near. I am Dinner Key Marina in Miami.
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Re: Blotches on deck - can you identify

Quote:
Originally Posted by zeehag View Post
looks like you polished thru the gelcoat to almost fiberglass...stop polishing. prep f or paint or gelcoating, which is prohibitively priced. is why folks paint their old fg boats.
I think we may have a winner here. Especially if you "had it waxed" as they normally use very high speed equipment and if they had a new kid they may have burned or took off to much gel coat. Welcome to the world of it is better to break it yourself rather than to pay someone else to break it for you, I mean do it your self, your not supposed to break things are you?
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