I’m no coffee connoisseur, but I can appreciate a newspaper and steaming decaf latte to start a lazy weekend; especially when my drink comes adorned with beautiful latte art. The baristas seem to be able to create hearts, leaves and tulips with a simple flick of the wrist and a controlled pour of the milk. Which made me wonder, how do they do it?! A few internet searches later and I think I have the basics…
Latte art is created from a mix of 2 colloids: crema and microfoam. A colloid is when one substance of insoluble and tiny particles are suspended in another. In the case of the crema, the colloid is a mix of coffee oil and brewed coffee. The microfoam is made through adding steam into milk and rapidly heating, this acts to denature the milk, changing the structure of the milk proteins but broadly leaving the amino acids alone – so the nutritional value is unaffected.
However, to get the microfoam “right” for latte art, the air must first be introduced at the top of the milk. This stretches the milk, adding small bubbles into the cold liquid. The air is then added lower, to ensure the air and milk mix properly. This explains why the baristas lift the milk pot up and down under the steam nozzle; whilst the tap of the jug on the table is to remove any large bubbles.
The barista may give the milky microfoam another swirl, to ensure the milk “polishing” is perfect, and then the good bit… with the 2 colloids good to go the pour can happen!
By initially pouring a high stream of milk it can get in under the crema without disturbing the surface too much. This keeps the crema “canvas” intact for the art to sit on. To actually make the latte art, the microfoam needs to be added closer to the surface. This is tricky as you are drawing with one liquid onto another, so both will move. When the milk hits the surface it flows outwards, so for symmetrical designs you need to aim for the middle. When you are down close at the surface you can pour faster to increase the “volume” of the design; though it’s a balance – increase the flow too much and you can ruin the crema canvas!
To get more complicated designs, not only do you have to control the height, you may also tilt the cup, milk jug and may need to stop and start the flow (apparently this is needed to make a tulip). For super intricate designs, baristas can etch into the art work. No wonder there are competitions, some of the designs that can be achieved are amazing.
There is so much more I could investigate, the chemistry as the milk denatures, the fluid flow of the two mixing liquids, the effect of the milk fat content, the difference between art in coffee and hot chocolate but, right now, I think I will go and make a drink… one instant decaf with a splash of semi-skimmed milk coming up.
Well you have to start somewhere!
There are a lot of sources of info out there on latte art, amongst others I looked at: