Food colourings have changed. They are now required to be ‘natural’. The chemical composition has changed, and so have the experiment results. Where once you could get a lovely blue streak through a celery or bright pink tinges to the edge of white carnations, you now get a big, fat nothing. And it’s all down to the food colouring.
The natural food colouring just isn’t concentrated enough, if you are buying the basic, run-of-the-mill, supermarket bottles. So, in the name of stripey celery, coloured carnations and good, honest Science, I started experimenting.
Firstly, I tried some different products on a pretty, and pretty interesting, experiment using milk. The idea is that the food colouring/ink floats on the surface of the milk, due to surface tension, and then, when a surfactant, such as washing up liquid, touches the surface, it disrupts the surface tension and the ink dances. Or so it would appear from videos and pictures, such as here or here. However, I believe these are all based on either American food colourings (where the legislation isn’t quite the same, or depending on your perspective, isn’t as strict. Maybe a vote in favour of Brexit? No more EU namby-pamby colourings. Britain could go back to the hardcore, hyperactivity-inducing, colour-your-insides-and-your-poo food colourings… Or maybe not. I digress…) or old fashioned food colouring.
I had found that, with the natural colourings, even with whole milk (recommended because the relatively higher fat, and lower water, content), they just seemed to coagulate and form weird deposits on the bottom of the pan.
So, first I tried some marbling inks. The inks had recieved good reviews on Amazon, so I thought it was worth a try. But elementary error. They danced and swirled around of their own accord. Of course they would – they’re ‘marbling inks’. The clue’s right in the name!!!
Still, not to be outdone by a mere ink issue, I bought some genuine, high quality, drawing inks. I would not be defeated by this! Except, I kind of was. They did swirl, sort of. But nowhere near as much as the videos suggest. And even with more washing up liquid, we couldn’t get the dancing past a slow, vague shuffle, rather than the full-on waltz you’d expect. I don’t know if this was due to the ink again – this high-end product has shellac in it, which helps preserve the ink when dried, forming a shiny surface on it (shellac is used in the food industry too, to make products glossy). I do know that when used in a walking water experiment (see here for more details) it formed a weird thick, gloopy substance after a few hours, so perhaps this was one to chalk up to experience.
There were still some other factors to rule out – depth of milk, fat content of milk (I’d used semi-skimmed with the last two experiments), type of dish… I would not be beaten.
I then moved on to the transpiration experiments, using carnations.
It started well enough.
I chose some nice, strong, vivid colours, cutting the stems on the diagonal as I would when putting cut flowers in water, added the food and left on the kitchen windowsill for a week or 2.
However, despite not running out of water, and the water itself being lovely and bright, it just didn’t work. Not a sausage. The flowers wilted and dried out, still perfectly white. I cannot explain this simply. It may that transpiration didn’t happen – perhaps there was an air bubble in the stems. But if this was the answer, how come my cut flowers usually last okay? Perhaps the colouring just wasn’t strong enough. The heat may have been too high, and maybe they just dried out before getting coloured, but I thought I would have seen the water in the jars go down significantly. In any case, there is clearly some work to be done here!!
I will carry on being a good scientist and I WILL find a way to make my celery stripey and my carnations coloured…
Watch this space!! I will prevail!!