Oak black marks in the sun

[rjm2k]

We bought a nice Oak toy box not long ago, it was left in the conservatory for a while and we noticed a large black mark appearing, initially we assumed water had dripped on it but it now seems that it's due to the sun (we moved it inside but still in the sun and another mark appeared). I'm assuming it's adhesive, but I guess it could be the oak itself. Is there any way of protecting it / preventing it from going like this more, other than covering the top?

tia

 

[AronSearle]

Sounds odd, pics?

 

[Dave54]

Blue black marks on oak are normally due to iron contamination in some way.
Ammonia will send oak brown to almost black over time. You need either long exposure or very strong ammonia though.
AFAIK the sun alone will tend to fade the wood if anything. Clean water will mark oak, but not blacken it.

 

[Jackrae]

cat pee perhaps ??

Oxcalic acid may remove the marks if they are due to iron contamination. Steel screws or fittings not recommended for oak unless you can tolerate some degree of staining.

 

[rjm2k]

I'll post a pic when I get home, I sanded the original off as much as I could but I'm told there is a new one. No animals in the house, I guess it could be rats from warehouse storage/transport but doubt it.

thanks