What happened to my meths?

After a year of storage in a (cheap copy of a SIGG) the meths for my trusty 30 year old Trangia was full of bits... more than that after making a cup of tea - the remaining fuel set into a gel:

At least it still burned OK...





But what caused it to go like this?

I can't see how any reaction between the aluminium and alcohol* could have occured at room temperature (if at all) - so the current theory was that the lacquer had become detached from the inside of the bottle (hence the observed floating bits) - and then the subsequent heat caused this to dissolve in the alcohol and form a gel.




* On research I find


"
One of the drawbacks of methanol as a fuel is its corrosivity to some metals, including aluminium. Methanol, although a weak acid, attacks the oxide coating that normally protects the aluminium from corrosion:

6 CH₃OH + Al₂O₃ → 2 Al(OCH₃)₃ + 3 H₂O

The resulting methoxide salts are soluble in methanol, resulting in clean aluminium surface, which is readily oxidized by some dissolved oxygen. Also the methanol can act as an oxidizer:

6 CH₃OH + 2 Al → 2 Al(OCH₃)₃ + 3 H_2"