Is this wood burnt or what?

[Jackrae]

Suggest you call Indiana Jones. The curse of the wooden elephants is upon you.

 

[NGEddie]

Your bubble wrap might have amplified the heat, like a magnifying glass effect. You can try wrapping it with a used paper as an alternative to bubble wraps.

sounds like a good way to start a fire

 

[AronSearle]

Would also concur, you need 400c for timber to char, it can happen at lower temperatures if those temps are held for longer periods, but your bubble wrap would burst into flames.

Very likely existing.

Or possibly and not very likely, it is decay caused by moisture trapped in the wood condensing behind the bubble wrap, decay can look black if combined with mould.

Decay tends to come off in fibrous clumps, char as charcoal flakes.

 

[Harbourwoodwork]

Perhaps the other half doesn't like it