Black spots on deck rails

[Beth n Rod 1,279]

Here's an interesting one for discussion. This is a photo of a rail system before washing. You can see there is a sealer, but on top of it are black dots - like splashes or drips. We washed it, and got it off, but does anyone want to take a stab at what it might be or how to remedy it before we disclose what we did to remove it?

Beth

[tropical wave 22]

hmmmmm, the top rail cap looks like its burnt, maybe from a grill lid when its opened (but it looks like the main deck is behind the rail), are the black spots on the vertical piece grease splashing?

be interesting to hear the story on this one....

[Russell Cissell 65]

That is an interesting picture. If the spots were in the wood as well as on the surface of the existing sealer I think the dark spots are what we would call a chemical burn. This is typically the result of an improper neutralization or rinsing of a caustic stripper.

This can be the result of not rinsing after you neutralize. Even though everything looks good when you've finish prepping the deck, the neutral salts build up can react with the finish and cause this type of spotting over time.

I was of the mindset to disregard what Michael said about the grill cover, but then I looked again at the pictures and had another thought. . .

I suppose that it is very possible the home owner may have been cleaning the grill. If they were cleaning it with an oven cleaner containing heavy caustics there could have been some overspray or splattering. The caustic cleaner could very well have left these marks.

The real tell would be in the way that you removed them. Did they come off when you washed or when you applied your acid?

[Beth n Rod 1,279]

I'll tell you all later....keep up the thoughts! This is a good learning thread. Not ready to give up the answer yet.

Beth

[Tronman 14]

The spots look like mold that leached through the thin top coat. The dark stain on the rail looks like oil of some sort. Possible a spill, drip from above, or high traffic point of some sort.

The dark spot looks like it was bigger but the wood has been striped away on both sides...

[Beth n Rod 1,279]

Cleaning the grill is a good observation....but the drops are on the outside of the rails, and under the rail caps, and I don't know that splash would go that direction.

Keep em' comming folks.

Beth :cup: ....more coffee...

[Beth n Rod 1,279]

The drips were prominent on most of the verticals and partially on the floors.

It looked to me that they were under the sealer.

The homeowner called it "a contractor disaster" and even told us that they didnt pay for the work since the contractor did not return to rectify this problem that showed up after the seal was completed.

Rod~

[Howard 50]

Looks to me like mold or mildew growth on top of the sealer. I wouldn't think it was the fault of the previous contractor. I would have (I'll get killed here) :lgbonk:used a solution similar to my house wash including (oh no here it comes):lgbugeyes bleach. Use low pressure and everything should clean up real well. I know, I know No bleach allowed, usually I'd use EFC38 or F13 but I do use bleach as well it does have its place in my tool box. Well there is my input. So Beth, Rod, what was it and what did ya do?

[Howard 50]

Ok so what were the spots and what did ya do to clean/kill/remove them?

:think:

[Mathew Johnson 123]

Was there something else nearby that was painted or stained?

[Beth n Rod 1,279]

No, this was the result of an improperly done job. There was no evidence of anything done to the home that would have resulted in this nightmare.

Beth

[Beth n Rod 1,279]

We have a number of different thoughts on what could have caused these and one person so far has hit it on the head.

Before we give it away, anyone else care to take a shot?

Rod~

[Mathew Johnson 123]

Was the stripper not completely neutralized prior to sealing

[jason c. 14]

sealed while wood was still to moist causing mold

[Aplus 525]

Was there a flower pot or planter box on top? Mold can grow from the moisture and drainage water that would drain out.

[Beth n Rod 1,279]

2 people have hit it so far.

I think it is time to give the answer.

The deck was washed and neutralized from the best of what I can tell, but there is many places where it looks as if someone took a sprayer with a caustic thinking it was a neutralizer and sprayed the areas effected. The result was spots of chemicals that were allowed to dry and once the sealer was applied, any water in the product reactivated the caustic and created the chemical burns below the sealer.

We stripped the deck and the spots remained, but when I applied the neutralizer, the spots disappeared. It took a couple of applications to get them all to be alleviated but in the end, the acid worked.

Russ and Mathew are the 2 who got it right with their guesses.

Thank you to all who jumped in on this one because it makes for some interesting and valuable information to benefit others who may come across this situation.

Rod~