I was using frothing wand in the past and tried using FP a few times, but milk taste was never even remotely close to the taste of steamed milk ...

Ended up ordering the Bellman and 500W hot plate. I'm hoping the workflow and extra heating time won't be too inconvenient, but worst case it should work until a decent electric steamer comes along.

jpender wrote:As one can see the rate of temperature decline was markedly less given this extra treatment. Preheating the piston, never mind the Robot body, for every shot would be a giant PITA in my view. If I had to do that I'd sell my Robot.

Charlemagne wrote:Sounds like a job for a heat lamp plugged into a smart plug!

I'm not really sure how much warming up the Robot itself mattered. If it were 10°C warmer that's only going to reduce inner/outer temperature difference by 15% or so. My guess is the boiling water on the piston is what really made the difference. Heating the whole Robot to near 100°C with a lamp sounds like maybe not the best idea to me.

I was going to do some more tests but I broke the fragile leads to my little probe (super skinny insulated wires that fit through the portafilter holes). I'm going to try again from the other direction -- through the pressure gauge port -- so the probe will be dangling below the piston. It's a little more complicated but if it works out it will be a permanent temperature readout for my Robot. I don't need to do this to make good coffee but it sounds like fun.

[edit: grammer correction - subjunctive]

jpender wrote: I'm not really sure how much warming up the Robot itself mattered. If it was 10°C warmer that's only going to reduce inner/outer temperature difference by 15% or so. My guess is the boiling water on the piston is what really made the difference. Heating the whole Robot to near 100°C with a lamp sounds like maybe not the best idea to me.

I was going to do some more tests but I broke the fragile leads to my little probe (super skinny insulated wires that fit through the portafilter holes). I'm going to try again from the other direction -- through the pressure gauge port -- so the probe will be dangling below the piston. It's a little more complicated but if it works out it will be a permanent temperature readout for my Robot. I don't need to do this to make good coffee but it sounds like fun.

I thought you pushed it through pressure gauge opening in the first place, wasn't aware of possibility to make it through the basket holes

On Flair, I made it through the piston (v1), after buying additional one (v2), by drilling the hole through it. Tip of the probe is now about 2.5cm from the piston surface, so that I know it comes in touch with shower screen / very near the coffee surface towards the end of extraction as it ends bent a bit. So I hope it better reflects the temperature that coffee puck senses than before when the tip was closer to the piston surface. Not sure what would similar change mean in Robot, from my remembering, Paul wrote that it (changing the length of the probe protruding from the piston) didn't make much difference in his measurements

I also don't think that heating the Robot body changes much, because piston is mostly in the basket and, as I understand, isn't touching the body

Still, from measurements so far, it looks like it's not easy if possible at all to make an average extraction temperature at something like 93-94˘C at my altitude ?

vit wrote:I also don't think that heating the Robot body changes much, because piston is mostly in the basket and, as I understand, isn't touching the body

The body is in contact with the portafilter.

I wanted to try a more aggressive preheat just to see what is possible. I didn't heat the basket and it has significant thermal mass. Maybe later.

jpender wrote: The body is in contact with the portafilter.

I wanted to try a more aggressive preheat just to see what is possible. I didn't heat the basket and it has significant thermal mass. Maybe later.

Yes, I forgot that "detail". But as I see from photos, that contact area is relatively small. And while some heat is obviously being transferred from top of the portafilter to colder body, as the pull is progressing, water level is dropping so remaining water stays away from that contact point. Temperature change along the portafilter downwards (because of that temperature loss) isn't instant - it shouldn't be very fast and shouldn't have much influence - or so I think

Anyway, I think that most interesting result would be the one that is relatively easily achievable - preheating basket and portafilter (like in Faema manual ?) - at some "usual room temperatures". Preheating body and piston as well would be probably too much complication for most people to use on daily basis

I've been toying a lot with my Robot, including the piston pre-heat. I don't think it's necessary at all but can be helpful.

I am still surprised that I and my wife tend to like the Robot shots better than those from my QM Vetrano. Maybe it's just the novelty factor. Maybe it's the more transparent shot characteristics of a lever-pulled shot. Fact is these shots are really good and hard to get wrong! I haven't had a single sink shot.

vit wrote:Anyway, I think that most interesting result would be the one that is relatively easily achievable - preheating basket and portafilter (like in Faema manual ?) - at some "usual room temperatures". Preheating body and piston as well would be probably too much complication for most people to use on daily basis

Relatively easily achievable is something that depends on the person. I routinely preheat the portafilter holder on the stove and find that this is very simple. I also usually warm the filter basket along with it, sometimes just long enough to take the chill off of it but other times to where it's too hot to handle. I don't know how much of a difference it makes with the water temperature profile but the filter basket comprises 21% of the weight of the portafilter holder+basket+screen. I think it probably has a measurable effect.

When I preheated the piston I thought it was too much trouble. But since then I've preheated it a couple more times and find that it's not really that hard to do. I don't need to do it; it may even be counterproductive given the type of coffee I've been using. But I think it falls inside of the bounds of "easily achievable". To maximize preheating of it (as opposed to simply soaking it in just off the boil water prior to the shot) would be more complicated.

Another thing that wouldn't be too difficult to do would be to insulate the portafilter holder with a sleeve -- neoprene or whatever. It wouldn't add anything to the workflow as it would just sit there all the time. I almost never have to clean the holder. In a similar vein, there may even be an advantage to sticking a piece of silicone on the bottom of the piston.

Warming up the Robot body? Well that's too much for me.

myso wrote:Is anyone able to measure the diameter of robot's dispersion screen disk?
I'm curious if it would fit in aeropress' brewing chamber (not the cap) which is about 56.8 - 57mm (what I see on my aeropress).
If it's bigger than 57mm, is the perforated diameter smaller than 57mm (do filing/grinding down to D<57 sound doable?)

57.66 according to Mr. Mitutoyo.