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Battery Acid on Teak Furniture

A flashlight leaked battery acid on a shelf on my teak bookcase. How do I remove the ugly stain?

Re: Battery Acid on Teak Furniture

I'm presuming that this book case had some sort of clear coat finish over the wood to protect it.

The first thing to determine is whether or not the acid penetrated through that clear coat or not.

Take a damp (not soaking wet) sponge and wipe down that stained area. You want to cover that area with a thin film of water, and I want you to try and notice two things while it's wet:

1. Do any white or white-ish areas of the stain largely disappear as long as they've got a film of water over them?

(If so, then the white areas are not a stain at all. That white discolouration is simply due to the scattering of light off a rough surface. It's the same reason why snowbanks, clouds and the head on a beer are all white even though nothing inside any of these things is actually white in colour.)

2. Did you notice if any of the wood got any darker when it was wet?

(That would indicate that the acid penetrated through the clear coat to expose he bare wood.)

Also, if you could hold a bright light at a sharp angle to the stain to see if there is anything sticking up from the surface of the shelf that could be carefully s-c-r-a-p-e-d off with a sharp paint s-c-r-a-p-e-r, I'd do that too.

It would help if you could describe the "stain" as best you can.

Re: Battery Acid on Teak Furniture

Thanks Nestor.The stain is about 3" in diameter where the flashlight was standing up.It is white and about a half inch wide by three inches I have not tried anything yet as I didn't want to ruin it.It just has an oil finish on it.I will try your suggestions. I had thought about putting water on it to neutralize it but I didn't want to rush it and then have a mess on my hands.I will keep you posted.Thank You

Re: Battery Acid on Teak Furniture

Go ahead and remove any residual acid by rinsing with water, but try to see if that water makes the white areas less noticable and any of the wood darker.

How do you know it was an OIL finish that was applied to the wood? If it was an oil finish, it will almost certainly have been either Tung Oil or a pre-polymerized oil like Danish or Swedish Oil. Tung oil is more expensive than linseed oil, but it dries to a harder film and yellows less than linseed oil. But, being a drying oil, it simply doesn't dry to as hard a film as polyurethane. Is there anywhere you could find out what kind of clear coat was applied to the Teak at the factory?


I just finished dipping a popsicle stick into 26% hydrochloric acid (aka: Muriatic acid), and it appears to have had no effect on the wood at all.

(aside: Photosynthesis uses the energy from the Sun, the CO2 from the air and the H2O from the roots to make sugar molecules in the leaves of plants. There are actually two different kinds of sugar molecules; lets call them A and B. If you stack up the A kind of molecule like bricks in a wall, you get starch, which is what potatoes, rice and cereal crops like corn, oats, wheat and barley are made of. If you stack up the B kind of glucose molecules like bricks in a wall, you get cellulose, which is what cotton and wood are mostly made of. Sugar is the only building block a plant has to work with, so everything in a plant is made from sugar molecules, or by modifying and combining sugar molecules in different ways.)

That popsicle stick test only shows that a strong HCl acid won't attack cellulose, but sulphuric acid might. Or a strong acid could discolour the stain applied to the wood before it was finished with a factory applied clear coat. Still, the fact that HCl didn't harm spruce is a positive indication that the battery acid probably won't attack the Teak.

Let us know what happens with the water test.

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