Jack and I went to the Science Museum tonight to run a workshop for their 'lates' programme. We've done quite a few workshops for their 'Science Night' programme (for kids), but working with adults opens up a few more possibilities! The theme of the night was 'alcohol', so we ran a version of our 'Chocolate and Orange' caviar using Cointreau.
It's a simple but fun demonstration using two food-grade chemicals that react together to form a skin around droplets of whatever flavoured-liquids you are using. The chocolate (and orange) mixtures contain sodium alginate (an algae derivative used commonly as a thickener in foods), and the water bath contains extra calcium ions. It is common to use calcium chloride, but we've ended up in most of these workshops using calcium lactate as it doesn't have a noticeable taste, so the caviar droplets don't need rinsing afterwards, making for a much quicker walk-up workshop.
It's always a popular experiment for people to do as you can eat the product of the reaction, and tonight was no exception. We think we had well in excess of 1000 people come through over the couple of hours we were there.
Many thanks to our Tech-Camp regular, Felix who stepped in for a little while at the start to help out when we were obviously in need of some help! (We didn't realise he was coming but he thought he would drop in with some friends from Imperial College next door, and fortunately he was even wearing the Tech Camp t-shirt!)