Surge boil - PLEASE READ

[Mash]

I immediately noticed the lack of 'thumping' during a run and have not suffered a surge since.

My advice is if you are experiencing a thumping noise and notice the lid lifting ever so slightly its time to act. Change your enhancers for new ones and add copper...

That is spot on. The Still should rattle gently. Big thumps are signs of trouble to come.

Remember always you are boiling explosive gases.
Stilling is quoted as carefully controlling a bomb and I think that's right. The airstill makes this task much safer by being smaller, less complex and electric. But we must not get complacent and forget what is actually happening is there.