I used to take a packed lunch to school, and I remember that Mum used to give me a drink of orange squash in one of those old Thermos vacuum flasks. For some reason these were quite often made with a tartan design printed on them, but I’m pretty sure mine was a solid colour. These flasks kept drinks hot or cold by virtue of the vacuum between the outer flask shell and the inner glass chamber, which had a reflective coating. Unfortunately this made the flasks easy to break, and indeed one day my flask innards were smashed after dropping my school bag.
After going through several replacement plastic bottles which all leaked, we chanced upon a new invention called the Roughneck Flask, whilst we were on a family holiday. It was still made by the Thermos company, but was made entirely out of plastic, and very robust plastic at that. In fact, the weak point in these flasks was the cup that screwed on the top, something which had normally been quite reliable in the old Thermos design.