I made a particular finding today with a frothing pitcher, and I haven't seen this said anywhere, so if it's already well known, I'll go about deleting this post. Here's the back story:
For months I've owned a "Quickmill Retro 0835" espresso machine, which uses a thermoblock for the boiler and steam function. I have never
made good milk froth on it. On a good day, I might be able to produce something that can look like something white floating on top of the brown crema. Not much, and I could not even come close to anything that I can use to do latte art. With the plastic frothing aid, creating foam for cappas is much easier. But as I mentioned in my last post here, it is a PITA to clean the steam wand with the plastic frothing aid attached. So I've taken to just using the machine without it.
But with no frothing aid, trying to produce anything I can work with on the QM is a pretty sad affair. Either I end up with underheated warm milk - that has no body, no microfoam to speak of. Or overheated milk that has curdled - broken up, as it's gone past its ideal heating point. Creating the whirlpool effect is not a problem, as I'm usually able to do that. And it doesn't matter whether the tip of the steam wand is submerged, riding the surface, a combo of the two, a steady hand, a non-steady swirling hand that heats up all points around the surface... it just doesn't matter to the end effect! While all these things do have an effect, I was just not able to create either good, plenty cappa foam or latte-ready microfoam.
I tried different pitchers, thinking this may be the key. I always do milk frothing for one person, and that's usually about 100ml of milk (between 80ml and 120ml). So I always wanted to use a small pitcher size. This aligned with reading comments from espresso people talking about how the milk should go half way up the pitcher; etc. Also, my QM steam wand has about 4" of clearance between the tip and top of the machine. So I can't exactly stick a milk jug in there. I had tried 4 different stainless steel pitchers/mugs; 3 are pictured here:
I usually used a size that's about 8oz. But I also tried a tall stainless cup (not pictured), about 12 - 16?oz. (similar to what you'd find in a stainless steel shaker). I also got a temperature gauge specifically for measuring the heat of the milk during frothing. That helped, but it didn't solve the problem of lousy frothed milk. (Mostly just heated milk that would end up actually cooling the coffee and producing a cup of lukewarm java... since the milk had to sit around while the espresso was being brewed).
Producing frothed milk is known to be one of the weak points of my machine (it has no variable steam output, and produces its steam power in short bursts of about 1s on / 3s off). Thus I resigned myself to the idea that I would never get the right results I want for lattes; or even cappuccinos. So I had to seriously start thinking about switching my beloved Quickmill for one of my other machines, that I know can do good milk froth. It seemed like after dozens and dozens of attempts, 4 stainless steel frothing pitchers (another one on order being shipped) and a temp gauge, the quirky thermoblock-driven steam wand just wasn't ever going to come up with the goods.
However, I did come across this item at a thrift store today:
It is HUGE, compared to anything I've ever used. I thought I would give it a shot, because at least it felt like a good quality. The bottom was stamped "ILSA", 18/10 (stainless), Made in Italy. But this monster pitcher is like 28oz. I've not heard of a frothing pitcher this big, so I don't know if that was its original function, or if it was meant for something other than espresso making.
However, when I did use it to froth milk... wow! It was, what they call a "revelatory experience". The milk did not behave as it did in all other attempts. For one, there was a much more marked difference notable when the steam wand tip was submerged or closer to the surface. Even the temperature gauge did not behave as before. I could not help but notice I had 3 times as much time to produce the desired effect before the temp gauge would reach the green zone (indicating the milk was at its max heating point). And when it did reach that max temp, I was still able to hold the pitcher, despite the blazing hot liquid inside. That's because the steel used is a quality, heavy grade of steel, quite unlike the very thin walls of my small, cheap 1 cup mug that I was using as a frothing pitcher (the all steel one pictured).
Actually, the ILSA pitcher got to that desired effect -before- even reaching the green zone! The effect it achieved was scads of thick ultra-creamy microfoam... and for the very first time with this machine (and probably any of my machines), I was able to easily coat the side wall of the pitcher. The elusive "wet paint effect", that I was always looking for and never really got. The foam produced on this first attempt, while perfect for cappas, was not quite what I was after for lattes... but its a very good sign that I can maybe produce latte-ready microfoam in subsequent attempts.
So I concluded from this something different than what "traditional wisdom" states in the espresso community (including comments I read on this site on this subject): that a smaller pitcher is better for frothing milk for a single serving of espresso. And that the design of my machine wasn't really what was holding me back. It was the very fact that the pitcher is large, meant the larger surface area would take more time to heat up, which meant you could inject more steam/air into the milk before your time is up, and you've hit the temperature ceiling and have to remove the pitcher and live with your results; sorry as they may be. The "more steam" allows for more foam. I also suspect the quality/thickness of the steel comes into play at a certain point. The shape I'm less sure about. It's a straight side (as opposed to one that slopes outward from the middle), but I did not notice any problem creating a whirlpool effect.