Cafelat Robot Temperature Tests - Page 20

A haven dedicated to manual espresso machine aficionados.
Honu

#191: Post by Honu »

Jpender
Those little blanket/heater things are cool :) curious if you somehow put them around the basket so in-between the handle assembly (we lock in) and the basket so its a complete basket handle used together ? I hope that makes sense what I am thinking
and then locked it in to preheat both the basket the handle and the piston ? Much like a basket is locked into the handle on a regular machine and preheat of everything at once ? much like pull a empty shot to preheat my baskets thinking but this time with just the blanket things
Reckon the handle would get hot of course :) but again thinking out loud

I know in my playing with preheat which for fun I did today because this thread hahahahaha
using the double spout blocked I use hot water preheating the piston and the handle and then the pour in and over I feel heats up the basket so everything is more up to level

jpender (original poster)

#192: Post by jpender (original poster) »

K7 wrote:Thanks for running the test and sharing the data. That looks not too shabby to me. Curious how the heating elements were applied...Do you think maybe 70 to 100W will do?
I was hoping to fit them flush against the metal and then covered with some insulation. But it's tight inside the piston and I had wires for sensors to contend with as well. So I just folded them up and stuffed 'em in best I could. The insulation I tried to add kept getting in the way of the inner arm struts and I ended up removing that. So it was a hack for sure.

Here's the inside of the piston. One probe going through the piston, one taped to the inner face. And the struts have to have some working room in there as well.




When I tested the heaters with the piston removed I was able to put insulation above them. The piston reached 60°C after 15 minutes. Kind of slow but installed in the Robot without insulation it took twice as long.

The bigger problem is that they were self-destructing. Folded up like that, and with no regulation, they overheated. I'm a little disappointed how easily the fabric mesh melted down. I think the fumes were poisoning me. So, yeah, more power, better placement/insulation, heaters with better thermal resistance, and probably regulation. I don't know what to try, actually.

I still think a passive solution is preferable. I can't make a plastic piston but I was wondering if I could make one out of wood, capped with silicone?

La Marzocco · Home: customized for espresso aficionados
Sponsored by La Marzocco · Home
jpender (original poster)

#193: Post by jpender (original poster) »

Honu wrote:Those little blanket/heater things are cool :) curious if you somehow put them around the basket so in-between the handle assembly (we lock in) and the basket so its a complete basket handle used together ? I hope that makes sense what I am thinking
and then locked it in to preheat both the basket the handle and the piston ?
I don't know if there's room for them. They are thin but the space in between the basket and portafilter is narrow. And to heat up the basket, portafilter, piston, and the water in the basket would take a long time. It might never get as hot as you'd like.

Honu wrote:I know in my playing with preheat which for fun I did today because this thread hahahahaha
using the double spout blocked I use hot water preheating the piston and the handle and then the pour in and over I feel heats up the basket so everything is more up to level
You're not only one doing that to heat up the piston. It's not as effective as a cup of hot water but if you preheat the portafilter/spout assembly (pour and dump hot water) and then fill it it works pretty well. And it does heat up the portafilter along the way.

Honu

#194: Post by Honu »

Yeah I got that Idea off the forum for sure not claiming it :) with the spout end :)
Have used a couple really nice heavy ceramic cups I have from when I drank milk based drinks that I know hold heat really well and I have tried that also the one I have happens to match the color of my robot !

Was not sure if they could fit in that space but interesting they might not produce enough heat in time then ?

Interesting to watch this thread though :) just had my nice 2nd espresso and came to check the forum life is good !

Jonk

#195: Post by Jonk »

jpender wrote:Sometimes preheating the piston seems to really improve the coffee, depending on the coffee. Other times it makes it worse. And there are also times when it's neither better nor worse, just different. That's how I experienced preheating with the particular coffee I pulled in this recent test. The roaster suggests a pretty high temperature, 95-96°C, which would be quite hard to maintain for an entire shot with a Robot. I like the coffee without any preheating but it tastes different when I preheat. So, I don't know what to say except I think it's worth having the tool in the box, so to speak.
I agree with John here. Just want to add that one of the reasons I backed the Robot to begin with was that it seemed impossible to ruin a shot with too high temperatures. Even with the open boiler I owned at the time I still had to make sure it didn't get too hot.

When used like Paul intended this holds true, and really I think it works fine for quite light roasts as well. The extraction yield can be on the low side and since I mostly drink light-medium roasts I often get a slight bready flavor without any pre-heating (but overall tasty and forgiving shots). Only for the extremely light roasts that are challenging with basically any brew method does it seem to be a real problem, with grassy and salty results. Even in this case it's more about the grind in my experience - a traditional espresso grinder will have a hard time with these kind of beans regardless of the temperature.

When I started to play around with pre-heating I quickly found out that it is not always beneficial to shot quality, hence my initial scepticism. Often it is just different (and slightly stronger). Contrary to popular belief there has often been an increase in acidity with increased temperatures - I think http://www.coffeeresearch.org/science/sourmain.htm offers a clue as to why. Either way I've concluded for myself that pre-heating the piston is usually helpful and a safe way to improve extraction and shot quality.

To get back on topic, my fingers really dislike most of the ways to heat the portafilter and basket. A careful overflow* is the only method I like, but I've noticed it's easy to overdo it and end up ruining the shot. Right now I'm using a light but delicate blend of washed and natural Ethiopian beans. Using water off the boil for the overflow will add a taste of cigarette ash to the shot. My workaround have been to use ~95C water instead and let it run for a while, say 10 seconds. I'm curious, how would a shot like that look on the graph?

* with an aeropress filter underneath the metal screen to prevent the puck from occasionally turning into an underwater volcano :shock:

jpender (original poster)

#196: Post by jpender (original poster) »

Jonk wrote:Contrary to popular belief there has often been an increase in acidity with increased temperatures - I think http://www.coffeeresearch.org/science/sourmain.htm offers a clue as to why.
Those data also appear in the old Lingle "Coffee Handbook". It's not surprising that the extracted acids increase with increasing temperature. Wouldn't you expect extraction to go up across the board? What is odd to me is that the acid concentrations decreased at the highest temperature.

What's missing here is the relative contributions of acid and sugar. In the Coffee Handbook there is an additional line for sucrose. It shows a larger increase for sucrose than any of the acids between the first two temperatures.

Jonk wrote:A careful overflow* is the only method I like, but I've noticed it's easy to overdo it and end up ruining the shot...
...Using water off the boil for the overflow will add a taste of cigarette ash to the shot. My workaround have been to use ~95C water instead and let it run for a while, say 10 seconds. I'm curious, how would a shot like that look on the graph?

* with an aeropress filter underneath the metal screen to prevent the puck from occasionally turning into an underwater volcano :shock:
That sounds suspiciously like a request. :-)

Jonk

#197: Post by Jonk »

jpender wrote:That sounds suspiciously like a request. :-)
It sure does :D

Also, interesting about Lingle. I wonder if what I describe as bready* flavor might be due to less sucrose. I haven't made the correlation that pre-heating increases sweetness but perhaps extra sucrose masks another flavor while being masked by more acidity.

* think whole grain, rye or perhaps cellulose.

I'm also leaning towards pre-heating being of more importance when using extremely fine grinds (made possible by a paper filter underneath the puck). Not only to balance the flavor but also to keep the viscosity low. Noticeably different backpressure depending on the water temperature.