Blue stain in wood from metal

[bluewhisper]

I'm listening to a radio story about an oak tree by Lincoln's burial vault, and an arborist said when they examined the trunk they found a blue stain in the wood, caused by nails. He said the acid in the sap attacks the metal, causing the stain. He said when a sawmill operator sees a stain like that he stops cutting for fear of hitting metal.

I'd never heard that before.

http://hereandnow.wbur.org/2015/05/01/lincoln-history-tree-rings

 

[Bearcarver]

 
I'm listening to a radio story about an oak tree by Lincoln's burial vault, and an arborist said when they examined the trunk they found a blue stain in the wood, caused by nails. He said the acid in the sap attacks the metal, causing the stain. He said when a sawmill operator sees a stain like that he stops cutting for fear of hitting metal.

I'd never heard that before.

http://hereandnow.wbur.org/2015/05/01/lincoln-history-tree-rings

Yup----Take an Oak board & nail it to a tree. Leave it out there in the weather for a few weeks/months.

It will look like the nail hole is bleeding blue/purple.

Oak Tannic (sp) acid & iron mix cause it.

Bear