Two weekends ago we had a family gathering to celebrate my mum’s 70th birthday. Mum & Dad had booked the Marine Villa at Archerfield for the weekend. The four of us flew over to Edinburgh on the Friday evening, with only a minor delay because of Storm Gertrude blowing through earlier that day. Nonetheless, we didn’t get to the villa until after midnight, and we were off to bed almost straight away. (After a quick tour of the villa, which is amazing.)
Our plan for the Saturday was to do a big family dinner, with Dad, Scott, and me each catering one course. Dad did a classic prawn cocktail, Scott made Tom Kerridge’s treacle-cured beef, and I made a trio of sorbets (mango, lemon, and raspberry & lime) for the grown-ups, and Cadbury’s Flake chocolate ice cream for the kids. (I had planned to make some vanilla icre cream as well, but I overcooked the custard and didn’t have enough eggs (or time) to do a second run.
Because I had been helping Alex with his chemistry homework over Christmas, I ended up watching a whole bunch of Brady Haran’s Periodic Videos. I was particularly fascinated with the one where they burn magnesium shavings in a crucible carved out of a block of solid carbon dioxide. “Wouldn’t it be fun to get some magnesium and try that out ourselves?” I thought. “Wouldn’t it be fun to play about with some dry ice?”
Turns out you can just buy dry ice on the internet! It’s not even all that expensive! I had a notion of buying a block of it in the summer and seeing what we could get up to. But then the family dinner came up, and I thought: dry ice ice cream.
I located some recipes for sorbet and ice cream, and practiced them the week before, but just with our standard freezer. The key to good sorbet and ice cream is small ice crystals. The smaller the ice crystals, the smoother the ice cream. You get small ice crystals by churning the mixture as it freezes (in an ice cream maker), thus never giving large crystals a chance to form in the first place, or by freezing it really really quickly. The best way to do this is with liquid nitrogen. You can buy liquid nitrogen on the internet, too, but storing it in the volume that suppliers typically want to sell requires an industrial dewar flask, and they’re expensive. But dry ice also works!
The technique involves grinding the dry ice to powder in a household blender, and gradually adding it to an ice cream or sorbet base in an ordinary mixer. The videos on the internet make it look easy, but we discovered that there are some subtleties involved. In particular: if you add the dry ice powder too quickly and don’t give the mixer enough time to distribute it evenly, it sinks to the bottom of the ice cream mixture and makes a solid frozen crust at the bottom of the mixing bowl. This can bring a small mixer to a worrying halt. It also doesn’t make for a nice, even consistency. I ended up discarding some of the sorbet as a result. If I did this again, I’d be careful to add the dry ice much more slowly, and use a high-powered mixer.
The other thing that some of the recipes and instruction sets warn about is a slight fizz and tang in the finished product. This is because some of the carbon dioxide dissolves in the liquid, just like in a carbonated beverage. When it dissolves, it forms carbonic acid. I made the sorbets in the afternoon and put them in the freezer for a few hours before dinner to try to give any excess carbon dioxide time to escape. Nice theory, but it didn’t quite work. Even the next morning, the left-over sorbet still had a bit of a tang to it.
However! It still tasted great, and it was great fun to make. I bought 15 kg of 3mm dry ice pellets (easier to powderize than a solid block) from dioxice.com. I ordered that much because I wanted to be sure that a) it would last long enough, and b) we had enough to spare that we could have some fun with it as well. And of course we did. Here’s the unboxing video, for example:
In the afternoon we had Rachel Rose round to do a photo shoot for the whole family. She did an amazing job, and we are super happy with the pictures. She took a bunch of traditional group portraits, and a batch of candid shots while we were hanging out and enjoying some birthday cake.
At one point we thought it would be fun to do a sequence of shots, in order of people arriving in Mum’s family. I stitched them together as an animated gif:
The following morning we disposed of the rest of the dry ice responsibly (cough). Then we had brunch at the Archerfield club house, swung through Dirleton so that Alex could capture a few locations for Ingress and hung out with Scott & Ange & Kyle & Rachel in Haddington for a bit before heading back to the airport. Abi and the kids flew back, while I stayed in Edinburgh for a few days of work. Overall, a highly successful birthday weekend.