Halloumi glass harmonica

For Channel 4’s Food Unwrapped I was asked why halloumi squeaks when you eat it. This led me to a demo suggested by a colleague Jon Hargreaves, where I played Ode to Joy on a glass harmonica, using halloumi to make the notes. But when I came to make it on filming day things didn’t work quite so well at first!

I’m holding a piece of halloumi in my hand

Why does Halloumi squeak?

This is a great example of stick-slip. The cheese sticks to your teeth, then as your teeth move the cheese stretches until it can hold on no longer, and then it slips. The sudden slips create the squeaking sound, that is carried to your ear internally, through soft tissue and between gaps in the skull! Halloumi is a rare squeaky food, it has just the right protein structure to be able to stick, stretch and slip.

Glass harmonica

Stick-slip also causes trainers to squeak on a gym floor, a violin bow to create a sound on a string, or the tone when you run a wet finger around the rim of a wine glass. The idea was that instead of a finger I should use a piece of halloumi, and then the TV will have a great demo. Tune five glasses to the notes needed in Ode to Joy and job done.

The video above was shot at home the night before, everything seemed simple. But it appears I got lucky when I tried it at home, when I was setting it up the next day at work for TV with different glasses and halloumi nothing worked!

Trying to find a glass that worked, the small ones were better.

The first issue was the resonant frequency of the glasses I had at work were too low. When you run a finger around a wine glass, the sound starts with stick-slip, but it then needs amplification to make it loud enough. The amplification comes from the resonance of the wine glass side. You can see how the glass flexes in this slow mo video.

By trial and error I found I needed a glass with a higher resonance frequency. The halloumi stick-slip just couldn’t lock into the lower frequency resonances from the large red wine glasses I had in my office. Fortunately I found some smaller wine glasses in the staff room at Salford, which while not brilliant worked a bit better.

Another issue is Halloumi is fatty, and therefore it tends to slip too much. Without “stick” you don’t get a note. I suspect in the mouth the saliva strips some of the fat and reduces the slipping. So I ended up washing my cheese in a lot of washing up detergent to remove the fat. That worked fine, but you didn’t get many notes before more fat oozed out and the sticking stopped.

I managed to get a rough Ode To Joy out, but it was a stressful morning trying to work out why it didn’t work first time, or second, or third …

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