How do you detonate chocolate spread?

I think we're all familiar now with the ban on taking more than 100ml of liquid aboard an aircraft in hand luggage.  Whatever we think about it, we are aware of the rule. But did you know ('cause I sure didn't) that the ban extends to gel-type products, which I think most of us would not think of as liquid. So toothpaste, face cream, marmalade and the like are all equally caught by the regulation. This came to my attention when a woman flying from London to Edinburgh had a couple of jars of Nutella which she had bought as Christmas presents confiscated as breaching the rule.  One thing which occurs is that such items are often sold by weight rather than volume - how on earth do you convert grams into millilitres?