It is Friday, the sun is shining, and there is a temporary lull in my marking, so I am reading about scientists making artificial urine. [You can insert, that is taking the p*ss joke, here if you want to.] Naively, you may think that scientists are wasting their time by making artificial urine. If they want urine why don’t just drink a lot of water and let nature take its course.

But they are careful experimentalists that want standard urine, that is always the same and so free of the batch-to-batch variability of the real thing. The reason they are going to all this trouble is quite serious: kidney stones. One is shown top right. If that forms in your kidneys and you have to pass it, it’s going to hurt. A lot.

Kidney stones are often crystals of a substance called calcium oxalate that form and grow in the urine in kidneys.

I am reading work by Fasano and Khan studying the initial formation of model kidney stones in artifical urine. Their results look consistent with a model I am developing for crystallisation, where it relies on a slow change in something in the solution, that then acts as a site for the crystal to start to form. So that is encouraging.

We scientists are often asked to work on ‘real-world’ problems, which is fair enough – part of my salary is paid for by taxpayers. And sadly kidney stones really do exist. It would be nice if I could contribute to a better understanding of how they form.