Removing dark water stains from wood

Hi All
We have some outside cupboards with doors made from cedar. In preparation t o re-oiling them my wife found that oxi-bleech (I think that's what it's ca lled) was a good way to clean them and vanish is a good source of it. Anywa y she cleaned them with it and they came up pretty well.
Several of the doors have drip marks left which are presumably where the ra in has been dropping off the top onto the doors directly. These are dark li nes running perpendicular to the grain. After some searching she discovered that it could be that the rainbow bringing the natural resins out of the w ood.
Anyone know whether this is indeed the case and what the best way of removi ng them is. I am loathed to sand them all again unless I have to.
Thanks
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On 16/05/2018 07:34, snipped-for-privacy@yahoo.co.uk wrote:

One possibility is iron impurities from hinges or metal fixings reacting with natural tannins in the wood when it got wet for a period of time.

I think a picture is worth a thousand words here. If the lines originate from mild steel fittings then my money is on iron staining.
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Will take some photos when I get home. I do have some of that from a few nails I had to pin from the front but the rest I can not think is. In one are the water runs off some stainless steel. Not sure if that would cause it?
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On Tue, 15 May 2018 23:34:42 -0700 (PDT), snipped-for-privacy@yahoo.co.uk wrote:

Oxalic Acid (widely available on eBay) is the most effective wood bleach.
https://www.woodfinishsupply.com/OxalicAcid.html

https://www.youtube.com/watch?v=YTHiqtdZMMI

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On 16/05/18 07:34, snipped-for-privacy@yahoo.co.uk wrote:

Beach or caustb canb work, but test on a small area frst. Different woods react differently and I have no experience of cedar.

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