Jo's Roman bottle glass

In the mid 90s we were visiting Vindolanda, a Roman fort by Hadrian's Wall when my daughter Johanna, then about seven or eight, found this piece of glass on a footpath. We reported the find, but she was allowed to keep it. It is a lower piece of a square sided quart bottle and you can see the right angle bend on the left of the pic. I have always kept this little artefact, and now Jo seems reluctant to take it back. I think she knows I am mesmerised by it. There is the colour, very blue-green, then there are the air bubbles, wee pockets of air that are 1700 to 1800 years old. That's the thing that gobsmacks me. I've never cleaned it, it is exactly as Jo found it that day.