Stained table top

[elisa123]

Have got this small wooden table (wood variety unknown) which was used as a plant stand for several years. It was standing in a sunny bay window. Removed the plants and got quite a shock about the state of the wood. The big dark stain on the right was caused by blue tack which kept a heavy flower pot in place. I have sanded the wood and it looks a bit better but I need some advice please. Could I bleach the dark stain before painting on several layers of varnish?
Thanks for any help.

 

[Deleted member 174758]

Well, it certainly looks like it could be solid wood (not always easy to tell on a small screen), but any chance of a picture of the edge so that can be confirmed? It would also help if the grain were more visible in a photo. It looks like it could be an oak, but TBH, it could also be another species

I suspect that the mark is a combination of sun shading and an iron-water reaction mark. Was the table originally much darker, say a golden oak colour?

 

[foxhole]

Hot iron over paper towel will draw out any moisture, keep iron moving and check frequently .

 

[Deleted member 174758]

Do you think it's possibly oil from the Blue Tac? Only ever seen small marks from this before, but never as extensive, though

 

[jbonevia]

Might be worth trying some oxalic acid to remove the stain.

 

[^woody^]

Put the pot back on a mat to cover the stain.

 

[elisa123]

Thanks for the advice. I think the oil from the blue tac seeped into the wood which was originally a golden colour. If I cannot repair it it will have to be covered up again.

 

[Deleted member 174758]

Assuming that any existing coating (lacquer French polish, etc) has already been removed, to try to get the oil out you might want to consider wiping the area with a white or unbleached cotton rag cloth (well washed old T-shirt) dampened with white spirits or isopropyl alcohol. This will take several applications. If it works, great!

If not, then the stain isn't oil, and being oak is likely to be black iron oxide staining, a combination of water (from watering the plant), iron (dissolved in the water albeit in minute quantities) and tannin in the oak. These react to create a black iron oxide stain which as jbonevia has stated can be reduced ir eradicated by using a solution of oxallic acid crystals dissolved in distilled water not tap water which may contain iron). It is best to make up a weaker mixture and apply several times rather than applying a very strong mixture once. The crystsls can be bought from finishing materials suppliers as well as the local chemist

Once the stain has been dealt with the original colour can be reproduced by seversl applications of a water-based wood stain built up to the desired tone, before a protective coating is applied

 

[elisa123]

JobAndKnock thanks for your detailed answer. I'll have a go next week and will report back.

 

[^woody^]

A liquid risks soaking into the wood too much, lifting veneer is if it is veneer, or raising grain and splitting wood when drying. You are better off using a gel product to revive the wood, or be very careful with liquid.