Oak water marks ?

[JFC]

I put some oak i had left over up on my spur shelving just to get it out the way a few years ago I didn't put sticks between the boards because i didn't think they would be there that long or need it . Anyway a job has come in to route some names into some oak so i thought i could save myself a few quid and use the oak on the shelves . I took it down today and there are water marks all over it . None of the other oak on the same rack has this and there is no water leak in the roof plus it was under a load of other oak . The boards are 225mm x 25mm and where stacked flat on top of each other . Anyone had this before ?

 

[Colin C]

Hi JFC
It can happen some times if the oak is still a little wet or has get damp with some water if it was out side for a little while.
You can get it out with Oxalic acid if it is already finished to size

 

[JFC]

It does look like its been left in the rain but it hasn't as there is no way id let oak get wet because i know how well it gets marked by water .
I think it may be the moisture coming out of the timber and because i didn't use sticks it couldn't escape . Nothing a shove through the P/T wont solve its just i've never seen this happen before .