I have a horrible feeling my T4 van's head gasket is toast

[Mr. Dazzle]

Sort of. There's definitely a lot of stress relieving and recrysalisation and aging required when working with metal.

Typically it's more scientific that leaving it out in the rain though

[mangocrazy]

I'd say there are probably advantages to leaving the blanks outside. Being outside it/they would go through cycles of heating and cooling whereas inside a building the temperature tends to be constant. Rain wouldn't really be a problem, as the outer surface would be machined off anyway.

[Mr. Dazzle]

Yeah but unless you build your factory on the surface of the moon I wouldn't have thought the weather was enough to matter.

[mangocrazy]

In Italy you'd get swings of nearly 50 degrees C in some years (+40 to -10) and regularly swings of 40 deg C. That would have an effect.