Bowl Finish Problem

[seajay62]

A friend asked me to restore a wooden fruit bowl. I believe it is walnut. The finish was worn off in areas and there were some black spots. (See attachments) Initially, I tried just cleaning the bowl by scrubbing with a paste made from baking soda. It cleaned up the bowl but still had uneven coloring and still some black spots at each end of bowl. I wondered if it is some type of mold so I tried soaking the spots with bleach but it didn't seem to change anything. Then I tried some light sanding and finally I tried using some "Citristrip" paint and varnish stripping gel. This is where I am with the bowl. I'm not happy with it and I'm not sure how to proceed from here. I'm asking for your advice.

[seajay62]

Pictures didn't get attached as the files were too large. I need to figure how to shrink the file size and will repost.

[edma194]

Don't know what kind of bleach you used. Oxalic acid is a good strong wood bleach. Be careful, it can blind you if it gets in your eyes.

[seajay62]

Here are the pictures. Topside of bowl picture doesn't have a crack but a piece of lint on bowl. Hope this a clearer picture of what I have.

Also, I used regular Clorox bleach.

Bowl Topside.jpg (540.16 KiB) Viewed 2030 times

Bottom of Bowl.jpg (322.88 KiB) Viewed 2030 times

Black spot Inside bowl.jpg (406.63 KiB) Viewed 2030 times

Speckle Inside Bowl.jpg (423.28 KiB) Viewed 2030 times

[edma194]

Clorox works on some stains but I don't find has any penetration. Any hardware store should have dry oxalic acid you can mix with water. Soak a cloth in it and let it sit on the stain for a while, it should work in minutes. Use some baking soda mixed in water to neutralize the acid once the stain has lightened. You probably want to treat all of the bowl to get it to a neutral shade before refinishing, just apply the bleach in individual areas based on how dark the staining is. Even if it all seems washed out the grain pattern should show again when you refinish it.

[RFGuy]

Are you sure the dark spots are mold? It looks like what I have found before working with redwood lumber. I believe what you are showing in your picture are stains from tannins. If indeed the bowl is made from walnut that makes sense because walnut is also a high tannin content wood just like redwood. As was suggested by Ed above, oxalic acid should help for this.

https://cswoods.com/blogs/news/oxidizin ... oxidation.