Newbie question about fixing a table

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rlrr
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Newbie question about fixing a table

Postby rlrr » Thu Aug 29, 2019 1:43 pm

Hi! I am a newbie here. I have a mango wood table recently given to me. It is this one: https://www.cb2.com/blox-35x63-dining-table/s123863

The previous owner damaged it. He placed a yoga mat on top of the table when storing it in his garage. He then stacked a metal chair on the table (he thought he was protecting the table by first placing the mat on it). When he removed the chair and mat, he found these dark vertical marks on it. My guess is that when the metal heated up this summer, it leached plasticizer from the mat onto the table.

I attempted to clean the dark area with white vinegar and water. I noticed that some of that darkened area has a different texture and that when wet, it started to peel off with just the back of my finger rubbing on it. So, you'll notice there is now a lightened area in the bottom left corner. That was where I attempted to clean it. It seems that the darkened area came off, but so did the finish because of the lightness there. I attached a photo that shows what it looked like when the dark area started to come off (it kind of crumbled off?)

My guess is that the damage permanently damaged the finish and that the only course of action is to remove the finish and refinish it. Is that correct? I don't have any experience with this, and also I live in an apartment so doing this outside in a well ventilated area is not really an option. I can open all the windows and a sliding glass door next to the table if a chemical is used to fix it... but if that isn't sufficient, I may need to just leave as is until I move. But if there's an option to use Restor-A-Finish or something to just make it a little better in the meantime, I'd love to hear it.

Anyways, let me know what you think my options are! Thank you in advance.
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Bob Boardman
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Re: Newbie question about fixing a table

Postby Bob Boardman » Fri Aug 30, 2019 10:28 am

First, I believe your best course of action is to remove the existing finish and apply a new finish. Dark damage such as what you describe is damage in the wood (not the finish), probably caused by a reaction between the plasticizers in the yoga mat reacting to the solvents in the finish. This usually comes from solvent finishes (not polyurethanes) such as lacquer, shellac or 1950's type varnish. The white spot usually means the damage is in the finish - this can also cause the finish to become degraded.

A dark spot can only be removed by removing the finish and bleaching (sometimes, sanding) the spot out

Before doing anything, I'd test to see what the existing finish is. Try rubbing a cotton swab dipped in lacquer thinner on a small area. If finish becomes soft it's lacquer. Repeat with swab dipped in denatured alcohol. If finish comes off it's shellac. If no finish softens or comes off with these 2 tests, it's a non solvent based finish. If it's either lacquer or shellac then removing the finish is relatively easy. If any other finish it's a bit more difficult. There are a number of waterbase (WB) strippers that don't give off the type of fumes you get with solvent strippers. Talk to your local paint store for suggestions. Follow directions on can. Let us know how you make out.
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Re: Newbie question about fixing a table

Postby rlrr » Fri Aug 30, 2019 12:56 pm

Hi Bob, thank you for your reply. I will try that.

Forgive my next question, as I'm a novice, but I am trying to understand: you said that usually when it's a darker mark it may be damage in the wood. However when I attempted to clean the dark mark off, I seem to have taken off a bit of the finish and the dark mark also disappeared, resulting in a very light colored wood underneath. This made me think the damage was in the finish only, but I could be wrong. Does that change your prognosis regarding the damage being in the wood too?

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Bob Boardman
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Re: Newbie question about fixing a table

Postby Bob Boardman » Fri Aug 30, 2019 1:01 pm

Yes - if you can remove the stains by removing the finish, then I would still remove the finish - - no need for any bleaching
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Re: Newbie question about fixing a table

Postby rlrr » Sat Aug 31, 2019 2:51 pm

Bob, I found lacquer thinner easily but denatured alcohol isn’t sold at Home Depot, I’m in CA. Would Acetone work as a substitute?

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Re: Newbie question about fixing a table

Postby Bob Boardman » Sat Aug 31, 2019 4:51 pm

No acetone won't work. Try regular household ammonia (not Sudsy ammonia). If finish comes off it's shellac
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Re: Newbie question about fixing a table

Postby rlrr » Sat Aug 31, 2019 5:02 pm

I tried the lacquer thinner on a q tip, nothing happened.
Does this work as (non sudsy) ammonia? https://www.target.com/p/lemon-scented- ... A-75557253

Thanks!

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Bob Boardman
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Re: Newbie question about fixing a table

Postby Bob Boardman » Sun Sep 01, 2019 9:53 am

You can usually buy a quart in a supermarket for a couple bucks
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Re: Newbie question about fixing a table

Postby rlrr » Mon Sep 16, 2019 7:36 pm

Sorry for the lag. I found out the finish by asking the manufacturer. It is finished with a water based clear lacquer followed by a natural wax. Let me know your thoughts on what's next? Thank you!

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Re: Newbie question about fixing a table

Postby Bob Boardman » Tue Sep 24, 2019 9:32 am

If the finish is lacquer (even WB) you'll need to remove with lacquer thinner. Follow directions on can.

When you think finish is removed, wipe surface with rag dipped in paint thinnner - this will highlight any finish still in place. When all finish is removed, wipe surface (esp the black spots) with laundry bleach. Wait 12 hours, most if not all black spots will be removed. Once done wipe down surface with a diluted vinegar solution, let dry, and stain and finish
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