While describing how to steam milk it seems like a worthy topic to insert how to do it without going broke if you don’t own your own cow…
When it comes to microfoam and latte art, I think the most important point is that the only way to learn is by lots of practice. This is why baristas who work at shops have a huge advantage over home baristas. They pour more drinks in one day than most of us get to pour in a year. Many claim that you should not practice except as many as you would drink yourself, but I think this is crazy advice – I certainly would not have learned to do it in my lifetime if I had followed it since most of my drinks are straight espresso so I would get very little practice if I followed it.
There are, however, very good ways to practice without spending a fortune on milk. The best is to take cold water and add a tiny drop of dish soap. This will simulate milk quite well and allow you to steam as many pitchers as you can stand for only a few pennies. When working on microfoam, this is a good thing to do again and again without ever even pulling a single shot. There is no point in practicing pouring latte art if your milk has large visible bubbles. You have lost the game before it ever even began.
Now eventually you will get to the point where you are producing reasonably good microfoam. At that point you will want to start trying to pull shots that you can pour the milk into. If you truly want to practice lots of shots in a row you still do not want to use bad coffee that is stale as fresh coffee that produces real crema is essential and coffee that is 2 months old like you might find in most grocery stores will not work as well as fresher coffee, but obviously if you are just practicing and are not going to be drinking most, very cheap fresh coffee should work very well. A number of good roasters offer a bargain price on 5 pounds of coffee if purchased at once and this would be a good way to go as you would get some great coffee to drink, some good coffee to practice with that does not break the bank, and probably still have a few pounds left to toss in the freezer for another day.
Below is a link I posted in a previous blog that shows this use of soap. It is by Scott Rao, the author of one of the best books on espresso out there The Professional Barista's Handbook