I was wondering. Does the band get more loose as you lose weight or does it get tighter?

it gets looser.

It will naturally get looser as you lose internal fat from around your stomach and over time, you do get a tiny bit of evaporation from the band too.

But you will need to fill it tighter and tighter most likely. As your body weight drops, you require fewer and fewer calories to maintain or lose weight and most people need more restriction to achieve this.

For example, I lost weight easily at first, rapidly and steadily, with an unfilled band. The amount of restriction I had unfilled was plenty. Nowadays, I require 2.8ml in a 4ml band to enable me to just tick along maintaining easily. The band got looser as I got smaller and I had to fill it tighter to maintain the same level of restriction.