AndyS wrote:Interesting <scratching head>

I second Dan's experience with the Linea versus the Aurelia; it takes a lot of sessions to get proficient. However, the GB5 and GS3, while not as easy as the Aurelia, may make it in two hours; they are a good deal more walk up friendly than the Lineas. A lot of this may be about simple things -- better initial "coldnose" management and smaller gicleurs on the newer LM models.

I got an hour on the GS3 at Intelly, and it has a far sweeter disposition than the older LMs

As I said before, the DB versus HX difference is very low on my list of deciding factors in espresso machines.

HB wrote:1. It's margin of error is quite small.
2. No. Perhaps if it were two weeks from now, I might reconsider. Maybe.

It's anecdotal evidence, but as an example, I tried the evaluation model Aurelia at Counter Culture awhile back and pulled good to very good shots from the get-go with no fuss, no muss. That just doesn't happen with the La Marzoccos in the main lab, I don't know why. It will be interesting to see how this changes the competition now that Nuova Simonelli is sponsoring the WBC, e.g., it may prove more difficult for a competitor to stand out on technical acumen alone.

I dunno about the machine in CC's lab, but mine is about the most ridiculously easy to use machine that I've ever come across. Perhaps it's due to updates in the design over the last several years. I'd expect the GB5 with Peirro group caps to be similarly easy.

-Greg

They have the GB-5 and an older Linea in the same room; I agree, the GB-5 is worlds easier to deal with than the Linea. But in my experience, La Marzocco has never stood out as newbie-friendly, though skilled baristas certainly have no issue with them. I thought the GS/3 was friendly, but any garden variety E61 is still easier for newbies, at least in my experience. Anyway, for those that are interested, this discussion prompted me to start Thought experiment of the week: Newbie barista competition.

As an aside, according to their technician, their GB-5 may be fussy because it has a tiny gicleur that keeps clogging. I didn't look at what he was referring to, but he explained that the gicleur is at the lower end of tube leading to the group. The smallest amount of scale can clog it. Despite that Durham water is soft and they have an exceptional Cirqua water treatment system, it starts acting up every couple weeks. Most Fridays begin with the tedious exercise of figuring out which group flows the most evenly.

I just plowed through all 7 pages of this in-depth discussion, plus Dan's great write-up ("How I Stopped Worrying and Learned to Love HXs"). I imagine you all might feel like every molecule of flavor has been extracted from this topic and also it's now six months later, but I have a question that, as far as I can tell, was not addressed in either place.

My question has to do with the stale or "dead" water that sits in the double boiler, a situation that reportedly does not occur with the heat exchange machines. Is that significant enough for me to disband thoughts about a double boiler?

I am a cappuccino/latte lover who is researching the purchase of my first-ever espresso machine, having settled the grinder-end of my investigation. At the moment I need a non-plumbed machine because I'm renting, though that may change in the next year or two. I'm willing to go up to the $1700-1900 range, possibly up to $2200 if the reward is great.

I was ready to pursue buying a double boiler because of the milk frothing/steaming capability and lower learning curve, but then I read a blog by Kat at Seattle Coffee Gear dated 3-1-09, around the same time that this forum discussion began, and also I talked with her on the phone yesterday. She said that the Italian espresso machine makers stopped making double boilers for commercial use in the 1970's and since then have been making them only for home use. Also, she talked about the "dead" water, or residual, that sits in the double boiler until the next batch, whereas the heat exchanger is constantly cycling fresh water through the siphoning system. This is not the same as having spring water sitting in plastic jugs, because the water can or does interact with the boiler. The link to her blog is below. Of note, Seattle Coffee Gear sells both kinds of machines, with the idea that there's a home for each.

I'd appreciate any comments anyone can offer.
Ann

http://blog.seattlecoffeegear.com/seatt ... oiler.html

ahhh... the stale water myth! always a good one.

Can water go stale?

And... as has been said a million times before... do not trust what equip makers tell you about their rationales for their decisions. The truth is that you DO need to backflush your machine with detergent etc. (90% of all equip decisions made by manufacturers is driven by cost and margin - and then post-rationalized with ridiculous justifications like this).

Straight water pulled through the group tastes of coffee regardless of HX or DB. Neither taste like fresh water.

Since heat exchange machines are continuously cycling fresh water through their siphoning system, they have an improved mineral balance and cannot become stale like the water in the double boilers might. So the flavor is significantly better and, therefore, preferred by connoisseurs the world over.

Heat exchangers cycle the same water through the heat exchanger until a shot is pulled. I seriously doubt a few parts per million change in mineral content while the water is in a double boiler is detectable by taste when the water is polluted with coffee and milk.

From La Marzocco, Italian Dual Boiler

The key feature of all our coffee machines is the dual-boiler technology.

To achieve a faultless quality in the cup we use a boiler dedicated to coffee brewing that is entirely independent of a second boiler used exclusively for steam and hot water for tea or other beverages.

This system, unlike the traditional system with a single boiler used by most coffee machine manufacturers, ensures a unequalled thermal stability, the determining factor for achieving a satisfying result in the cup.

Another advantage of the dual boiler is the quantity and quality of the steam dispensed, greatly superior to any other coffee machine

She said that the Italian espresso machine makers stopped making double boilers for commercial use in the 1970's and since then have been making them only for home use.

This is completely false. La Marzocco, an Italian company, has been make dual boiler machines for commercial use for decades. You'd think Seattle Coffee Gear would be aware of this.

Thank you Malachi, Ian and Beezer for being so quick and helpful, and for debunking the stale water myth (I like your humor). I looked up the Marzocco link per Ian and Beezer, had a little fantasy-thought about the GS3 and then read Dan's comments that it's not very user-friendly for newbies, and finally I spoke with Phil at Caffe Lusso.

Phil is a proponent of dedicated boilers and calls the Marzocco GS3 the "Ferrari" of home espresso machines. He said nearly every good micro-roaster in the U.S. is using a dedicated boiler (specific for every group head). Another myth debunked. Also, he said the Marzocco and most, if not all, the double boilers, are made of stainless steel, so unlikely to interact with water stored in it. Last, was his comment that the quality of the water is much more significant than the sitting of it (my paraphrase).

So unless there are other comments to come, I thank the three of you for your time and your help. I think this question has been put to rest, at least for me.
Ann

Ken, thank you for chiming in. Those are very helpful notes about back-flushing and draining (from Malachi and Ken). Also, I would think if the double boiler is used regularly that it will automatically become empty approx. a couple of times a week.

This myth seems to have been well and truly debunked, even dunked!

I find these forums to be a treasure-box full of help and support, which is what I've found with the four of you. My thanks to you all.

All I see is more myth making, with no experimental evidence on either side. Just to play devil's advocate:
* practically every recipe for brewing tea or coffee emphasizes the importance of starting with fresh cold water, not water that has been sitting in a boiler
* in addition to picking up minerals and metals, water that has been boiled in an open container loses oxygen and tastes "flat"
* water is the major constituent of espresso, so even small changes in composition may have an impact on taste

Based on the above, it appears that the burden of proof lies equally on both sides. IMHO, starting with fresh cold brew water is a benefit of the HX design, although I'd be the first to admit there is no hard evidence to support this belief.

I'm currently using a DB machine (Spaz S1) with a large (2.5L) steam boiler and a much smaller (0.45L) brew boiler. One advantage of this design is that the brew boiler water gets replaced rapidly, even under light use. Other manufacturers have chosen much larger brew boilers, sometimes putting steam and brew boilers of identical volume in their DB models. The logic behind this (identically sized boilers) escapes me; perhaps it has to do with parts availability rather than good design.

You can say that the hx machines start with cold, fresh water only if you can persuade me that the group flushing regimen in use completely recharges the hx with the cold water you mention. I don't think that's the usual case.

-Greg

gscace wrote:You can say that the hx machines start with cold, fresh water only if you can persuade me that the group flushing regimen in use completely recharges the hx with the cold water you mention.

The HXs on semi-commercial / prosumer units are tiny (~120 mls). HX "dragons" like the Elektra Semiautomatica, Olympia Maximatic, Gaggia Achille, Expobars, etc. flush the HX completely and then some. The commercial HXs of the Cimbali line and the Nuova Simonelli Aurelia, for example, have much greater volume, require very little flushing, and are therefore an entirely different story.

Good point. Again, no evidence to present. However, home machine HX volume is typically small (about 100ml), so there's a far better chance of a (near) complete flush than with virtually any DB machine.

Oops, sorry for the cross posting.

RapidCoffee wrote:I'm currently using a DB machine (Spaz S1) with a large (2.5L) steam boiler and a much smaller (0.45L) brew boiler. One advantage of this design is that the brew boiler water gets replaced rapidly, even under light use. Other manufacturers have chosen much larger brew boilers, sometimes putting steam and brew boilers of identical volume in their DB models. The logic behind this (identically sized boilers) escapes me; perhaps it has to do with parts availability rather than good design.

Most of the arguments in favour of "fresh" water seem to take it as a given that obviously fresh water is best. The ones that engage with the subject matter a little bit more go on to point out that heating water for a long period of time will drive off dissolved oxygen. Frankly, this strikes me as a case of a little knowledge being a dangerous thing. I can remember reading the dissolved oxygen tidbit in a few places, but I can't remember any sources that actually did taste tests. Perhaps I'm missing some actual research, but it wouldn't surprise me if this is a case of people concluding that obviously it's better to have more oxygen dissolved in the water if you are brewing coffee. Which is quite funny because when coffee is in air instead of water, everyone seems to agree that oxygen is a bad thing. At any rate, if you pick up a copy of Sivetz' Coffee Technology book, it actually states that water should be boiled to drive off all dissolved oxygen before brewing coffee. I thought that it was worthwhile having an informed opinion on this, rather than conjecture, so I did some triangle cuppings using the same coffee, but comparing water brought just to the boil against water boiled vigorously for 25 minutes. FWIW, I couldn't pick the difference. I wouldn't claim that to be a thoroughly researched and statistically valid study that everyone should look upon as gospel and I'll repeat it again when I have time, but, in the meantime, I won't be losing too much sleep over the whole "fresh" water thing.

As for the logic behind having a large brew boiler in a multi boiler machine, I think that one of the reasons is that if you have a large mass of water relative to a small mass of metal, the whole thing is more likely to reach an equilibrium faster, seeing as the water can assist in moving the heat around. If you look at a LM or Synesso saturated group, there is so much brew temperature water there, immediately next to where the portafilter locks in that you have to think that the temperature change as you start to pull shots will be fairly minimal. A while ago, I popped into the cafe where I used to work to check out a new machine that they had been loaned whilst the Synesso was being rebuilt. It was a multi boiler machine with a massive steam boiler (great!) and three small brew boilers, which were bolted on to groups that were not saturated like the LM groups; I like to think of them like "chunk-o-metal" groups. The shots started to taste more astringent as the day went on and this problem was alleviated somewhat by dropping the boiler temperatures to compensate. Our guess was that this was the effect of the group heads heating up as they were used more and more - I think that Abe observed the same phenomenon in his brewtus review. From memory, the S1 has a similar setup. At any rate, I think that everyone was relieved to get the Synesso back.

Another part of the equation that I don't know much about is how the water in the boiler actually behaves. Water doesn't heat uniformly throughout the body; the water nearest the element will heat up more than the water furthest away and then you get currents with the heat moving around. This adds a whole level of complexity to dual boiler and group design, when you consider that just as you can only stabilise the temperature of the water at the point of the probe, you only draw water at one point. Interesting stuff.

Cheers,
Luca

Well, it seems I spoke too soon. This tale of Water on its way to Union with The Bean, is not done. And the myths now look both ways.

It's helpful for me to hear about all the ways the water is changed out, emptied, etc. between the DB and HX, and to consider Luca's outside-the-box question about whether fresh cold water really is the Holy Grail.

I'm wondering if it's worth asking this water question of one or more manufacturers that make both DB and HX machines; or equipment retailers who sell both? If so, would likely manufacturers be Izzo, La Spaziale, or Vibiemme? For retailers, perhaps Chris of Chris' Coffee?

An interesting discussion on many levels.
Ann

P.S. RapidCoffee, I had to laugh and wonder about your "cross posting". I thought of cross-dressing, posting across forum boundaries, and at last it occurred to me you meant cross disposition---am I right?
Ann

lattelover wrote:P.S. RapidCoffee, I had to laugh and wonder about your "cross posting". I thought of cross-dressing, posting across forum boundaries, and at last it occurred to me you meant cross disposition---am I right?

Nothing nearly so kinky. By cross posting (perhaps a misuse of the terminology), I simply meant that Dan and I composed our posts at the same time, and he got there first.

luca wrote:...I did some triangle cuppings using the same coffee, but comparing water brought just to the boil against water boiled vigorously for 25 minutes. FWIW, I couldn't pick the difference. I wouldn't claim that to be a thoroughly researched and statistically valid study that everyone should look upon as gospel and I'll repeat it again when I have time...

Best argument I've heard yet on this thread. Thanks for taking the time to actually try this. Experimentation beats angels dancing on the head of a pin any day.

luca wrote:As for the logic behind having a large brew boiler in a multi boiler machine, I think that one of the reasons is that if you have a large mass of water relative to a small mass of metal, the whole thing is more likely to reach an equilibrium faster, seeing as the water can assist in moving the heat around.

The downside: changing the brew temp (especially reducing it) takes longer with large brew boiler volumes. Dunno if I agree about equilibrium; I'd guess thermal gradients are a bigger problem with larger boilers (but that's more dancing angels).

luca wrote:...The shots started to taste more astringent as the day went on and this problem was alleviated somewhat by dropping the boiler temperatures to compensate. Our guess was that this was the effect of the group heads heating up as they were used more and more - I think that Abe observed the same phenomenon in his brewtus review. From memory, the S1 has a similar setup.

Rising brew temps have been noted on several home DB machines (especially those with E61 groups). I haven't had noticeable problems with the S1, but my usage is far lower than a commercial cafe.

There's two issues here, the silly oxygen one, and the much more reasonable leached metals one.

The colder the water, the higher the equilibrium of dissolved oxygen. By the time the water gets to near boil, there is almost no dissolved oxygen. This is a non-issue.

Why do people tell you not to drink or cook from the hot water tap? Because the water has been held in storage heaters and has leached metals. Copper boiler water has a relatively high TDS from this too. There is no health hazard I know of, unless you chose to do your entire water intake as Americanos, but it still puts heavy metals into your system. Instant hots and hot water dispensers are steel or plastic lined for this reason.

IMO, this isn't high in the list of concerns when choosing an espresso machine. For instance, I think the poorer energy efficiency of double boilers is a greater public health hazard than leached copper from HXs. But I doubt either amounts to much.