Aerated coffee

I’ve another post coming on why I blog, but this reason deserved a post in its own right.  A few days ago Shaun dropped me an e-mail about the Vinturi.  He’d played with it a little bit and thought it was interesting, and thought it might be something that would interest me. I admit I was curious – so I grabbed one from the UK website.  (Clicking through may help explain the image above!) Continue reading “Aerated coffee”

A grand unified theory of espresso

Not too long ago I posted on Home Barista about trying to find a good way to measure the density of coffee beans.  1

As always the paricipants there were way smarter than me and offered several interesting options. I dropped into the thread that this was part of my idea of a grand unified theory of espresso, and subsequently a few people mailed and pm’d me asking what on earth I was talking about and what density had to do with it.

Well, I should probably explain what I have been thinking.  2

Continue reading “A grand unified theory of espresso”

  1. There really is no better place on the web for these kinds of questions!  ↩︎
  2. Some of this is based on personal preference, some on what seems to be fairly well agreed upon within the community of people who worry a lot about their espresso.  ↩︎

I’m very excited!

Got a phone call this evening about a little machinery project that we embarked upon with Marco, telling me that they will be debuting the machine at CatEx – Ireland’s HORECA tradeshow – between the 9th and 11th of February.  It was an idea we had that they agree to R&D, and the data coming back from testing was impressive.

At the moment I still can’t give much away, it is nothing to do with espresso, it isn’t a coffee brewer either but I hope it will be great.  I have yet to see a finished unit, and I gather the aesthetic side is still quite open.  I’ll likely be heading over on the 1oth for a quick play with it, and to make coffee for people at the show and to talk about the project a little more.

Like a kid in a candy store…….

More on the French Press Technique

After the last post there was a bit of discussion about this method.

One big question was:  “Why break and then skim?  Why not just skim?”

This seemed like a pretty good question to me, so today I decided to do a few quick tests.

I took two identical presses, the same dose of coffee, the same brew water, temp and time and then after 4 minutes broke and cleaned one, and just cleaned the other.  I then tested out the TDS in each cup of coffee.

A TDS meter is useful, but limited.  It will tell you how much is dissolved in the water and nothing more.  Here I wanted to see if one cup was stronger than the other.  It turns out one was – and by quite a significant percentage. 1

The broken and stirred cup was stronger, usually by around 0.2%.  This doesn’t sound like much but when you do the maths backwards you find that it is a swing of about 3% of the ground coffee solubles extracted into the cup.

I want to do some more tests on this, and I want to do some blind cupping of it as well.  However it would seem that if your grinder produces a lot of fines, and when making press coffee it seems to easily overextract then I would just skim, opposed to breaking and skimming.  It could be that a different dose and steep time could yield better results.  I am waiting for Mark Prince’s article on his press technique because I know that while he skims but doesn’t break he does use different parameters.  It may be that one style might highlight a certain coffee better than another, who knows – I am just interesting in learning more about all this.

  1. It should be noted that I haven’t done this experiment enough times for it to be seriously useful – if anyone out there with a TDS meter wants to contribute then please do!  ↩︎

TDS, Chemex and London’s terrible water

So thanks to the lovely people at Bunn I have a couple of TDS meters and have begun to poke them into various coffee drinks.

The first thing that upset me was just how hard London’s water is. Out of the tap I get 410ppm, which is pretty hard. This means it is not ideal for brewing coffee as it is less “hungry” for new solubles than softer water. I didn’t realise until I started testing just how badly it was affecting the coffee.

Chemex and TDS

Testing some of Tim’s coffee brewed on the skinny Chemex

I was struggling to get into the Golden Cup zone of 18-22% extraction which, through years of filter brewing, is considered a suitable target. Different countries might like different strengths of coffee but they all generally like 18-22% of whatever dose that is.

I have know switched to bottled water for brewing (with a much more attractive TDS of 130ppm) and the coffee does indeed taste much better and my extraction percentages are up even though I haven’t changed the grind or dose. I had gotten used to a very coarse grind on the Chemex (after being advised by Kyle in but have slowly been bringing it finer to get the percentage up. I will keep doing more but wonder how many other people out there have TDS meters and whether they have compared their brewers with different grinds and doses and compared the cups after.

To this end I’ve done a little spreadsheet that negates the need for a brewing chart as the maths is built in. It works on 2ml of water being absorbed by each gram of coffee but you can change that too. Input the amount of coffee you use, the amount of water you brew with and then TDS measurements. I’ve left columns in there for other useful data – such as brewer, coffee used and notes on grind settings. I probably should have found a way to include a cupping score/notes but haven’t. If anyone else fancies having a go then do download it and let me know how you get on. Once I have enough data I will post up about my Chemex experiments.

Thoughts and comments welcome….

XLSTDS Testing Spreadsheet


Mike Khan from Bunn sent me his spreadsheet which does percentages and graphs for each brew you do.
XLSMike’s TDS Calculator


Thank you Mike!

5 Predictions for Coffee in 2008

Having looked back at 2007 I am going to go out on a limb and have a go at a few predications for coffee in 2008, though try and keep them fairly general.

The spread of the Clover

I am hoping this year sees people less obsessed with it as new technology and start to treat as a standard brewing device moving emphasis away from the machine back to the coffee. I could be really brave and predict that Starbucks will start using them, but I think the guys at Clover would curse me for jinxing them! I also predict I’ll buy a couple this year, but I am fairly sure that will come true…..

Clover puckClover puck

World Barista Championships

I am not going to be as bold/stupid as to try and pick a winner but I think the shift away from a Scandinavian-heavy final will continue. I am not saying that none of the Scandinavian countries will be there, or that a Scandinavian won’t win, just that the rest of the world has caught up (in competition terms) and that it really is incredible open. I can’t wait to see the performances in Copenhagen!

Coffee prices continue to rise

Whilst I am aware that Speciality pricing doesn’t have an absolute relationship to C-market pricing, but I think a lot of factors will help drive up pricing. Those of you who keep an eye on the coffee news feeds will see a lot of stories about reduced production in a lot of countries, plus the increasing demand for high quality coffees is (I’d guess) rising slightly faster than production is which will also push up pricing. I suppose, as someone about to start buying green, I ought to wish prices would stay low but I love the idea of what increasing spends could do for quality of the ripe cherries picked and the greens produced.

Pressure profiling in espresso

I know this isn’t a new idea, but I think 2008 and could be the year people are willing to experiment more with it and equipment mods/hacks get easier to implement. The open source nature of the internet could help contribute to a faster “dialling in” of profiles as people share their experimentation. I think that improvements could well be made outside of a flat line profile and if anyone wants to point me in the direction of how to install some sort of pressure profiling device onto my GS3 I’d be very grateful, or tell me if I should just do it on a one group Cyncra.

The continued rise of the micro-lot

Hopefully the term and the concept will spread further and further. I love the idea of one or two dozen bags of something special, something fleeting and interesting for consumers and another way to inject more money into farm level. Highlighting both seasonality as well as varietal, terroir and processing I think they are a great bridge to customer interaction.

Plus I need something different and tasty to drink from my growing range of mugs (which I hope become as collectible as espresso cups!)

Cup of Tim Wendelboe's Guatemalan microlotA cup of Tim Wendelboe’s Guatemalan microlot

So – what are everyone else’s coffee predictions? Leave a comment, post a reply on your own blog – what do you see changing? What do you want to change? New products? New ideas?

An experiment to determine freshness

Freshness is one of those difficult terms in coffee because it is often considered quite subjective.

However I was thinking about brewing stale coffee as espresso, and then thinking about measuring filter brewed coffee and an idea cropped up.

To me, when I brew stale coffee as espresso it seems that there are a lot less solubles in the brew – the pour looks very pale very quickly, if not all the way through the shot. So based on this observation I propose an experiment using filter coffee.

Roast up 5 kilos of a coffee and then set up to brew as filter coffee so that the percentage of extraction is around 20% for the chosen weight of coffee. (The brewing charts may differ on ideal strength but they all agree that 18-22% of solids extracted is considered ideal.) Let’s say we use a Nordic dose of 70g per litre.

Once this grind has been set for that dose then 3 brews a day are done for that recipe with a fixed grind (the grinder kept cool – no back to back grindings). The resulting brews are then measured for TDS, as well as the brew water so an accurate log of extraction percentages could be kept. This daily experiment is then repeated for 30 days and the results graphically logged.

The coffee could be kept a number of different ways for each type of experiment – craft packaged, valve packed, valve packed and nitrogen flushed.

I would hypothesize that though everything was kept constant (grind/dose/brew temp and volume) as the coffee aged it would start to be more difficult to extract. Whether you chose to see the point at which the coffee drops below 18% as the point it is stale, or perhaps another point that has some repeated statistical significance I don’t know. However I think that one could likely find enough data to give a reasonably accurate shelf life for truly fresh coffee.

It would also be interesting to couple the metering tests with cupping, but I worry that it would be too difficult to be objective/difficult to set up well.

I am sure this has flaws and would welcome any input on this before I start to play with it. (Plus I need a TDS meter!)

Thoughts in the comments please?

Brew Temperature and the Chemex

I remember reading early in my coffee days that someone had done an experiment where they had compared heat loss in porcelain espresso cups of different thicknesses and found that the heat retention of the porcelain didn’t much matter because all the heat went out of the top anyway. Like a lot of what I read on the internet at the stage I didn’t question it, didn’t want to see data but instead found it interesting, tucked it into its little trivia box in the brain and moved along.

After some comments in the thread about using scales to brew my Chemex on brew temperature I decided to perform a few rounds of experiments. Simple really, I just placed a probe (K-type, not ideal but it will do) into the bed of coffee, poured over the water and waited to see what would happen. The first test gae me an unexpected result.

Brew temperature of a Chemex

Brew temperature of a Chemex

What I expected was a steady decline in temperature during the extraction, and over a couple of minutes losing a fair few degrees, due to the area of steeping coffee being quite large. When the probe was in at the top of the brew the total heat loss was about 2C. Not much at all. What was interesting also was the temperature gradient throughout the liquid. At the start it was a couple of degrees from the top of the brew to the point of the filter cone and over brewing that stretched out to about 4 or 5C.

I’ve only done this experiment a few times so if you have the kit and a few extra minutes to spare I’d love to see it replicated – the coffee coming out isn’t much affected by the probe so it isn’t a wasted cup in the morning.

To completely and utterly hypothesize – it seems the floating crust of grounds does wonders for insulation, possibly with the help of CO2. In the next round I’d be tempted to stir and skim like a cupping bowl to see if this accelerates the cooling.

Thoughts anyone?