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Medium Roast extraction issues


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Hi guys,

I need some help and advice, as I'm struggling to get decent results from a new Light/Medium Roast bean (Beacon, by Foundation Roasters). I've used a combination of Gaggia Classic 2019 (new) and Eureka Mignon Specialita for the past 2 months with decent success, using mainly dark and forgiving roasts; examples including Pact Coffee's Zaroca, @BlackCatCoffee Twilight,  Chocolate Point, Fazenda Terra Prata and Ilona Decaf and Union Revelation. Barring occasional variations I've had excellent results. Gaggia Classic is stock, except the 9bar mod from @MrShades . No PID, although that is planned in as an urgent mod! All coffee is stored in airtight containers and used soon after 10 days from roasting. Grind settings have been as follows: 

Burr touching point: -0.8 : this has not moved.

Grind Setting: +1.5 to 1.9, depending on which of the above coffees I've been using.

So, net grinder movement from burr touching point between 2.3 and 2.7

Consistency of the grind has been fine table salt. I level and then tamp and use a La Marzocco 17g basket (aka VST 18g). Results for the above are as you'd expect: 18g in, 36-40g out in around 30s, with obvious variations according to coffee.

But then I tried the Beacon Light/Medium roast. Their roaster recommends a ratio of around 1:2.2 at circa 92c, in around 32s, but as mentioned, I don't have a PID, so the temperature element is the usual lottery. 

I started at 1.8 on the Mignon: 18g in, 39g out, 14s(!). I progressively reduced the grind down to 0.5 (so 1.3 from touching point), pulling the shot 10 seconds after the brew light comes back on. Barely discernible movement in terms of running longer (16s now). I'm preparing the puck by stirring with a pin, and it doesn't look clumpy (pics attached, before and after tamping). Final attempt was 16g in 36g out in 25s: I waited 60s after the brew light came on in a vain attempt to extract something remotely palatable - still extremely under extracted and the grinder now at -0.3, so only 0.5 from the burrs touching. It is Turkish coffee texture at this point in everything but name! Pics of the before/after tamping and resulting sludge. Difficult to film the bottomless portafilter due to the high standard drip tray. There is channelling: 3 noticeable starting points, merging to one after about 5 seconds, then speeding up rapidly. At this point, it looks fairly central/even. Any advice welcome please! 

 

 

Before tamp.JPG

After tamp.JPG

Result.JPG

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How does the coffee actually taste? Sour I suspect?

My gut feeling says to keep the grind and dose as it was for your last shot (for now) and stretch the output out to perhaps 3 or 3.5 and see how the affects taste. Don't get too bogged down in the time.

David

 

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You can increase dose or grind finer. If you're single dosing the Mignon then try running with the hopper full and you'll find you don't need to have the grinder adjusted so fine. You can also increase the output. 

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Lighter roasts will tend to mean setting a grinder much finer than usual. Medium should be easier but the word light is mentioned. As the burrs are set rather close to each other this makes exact adjustment much more difficult. The roaster only mentions medium roast - no mention of lighter.

3 fine streams going to one isn't toooooo bad really. We'd all love straight into one immediately. One thing I found that encourages 3 is the 3 wing distribution tools.

Do you tap your grinds down after stirring? Might help but only if the grinds remain level. Doing this can show if you have uneven grinds compaction due to stirring. It can clump grinds in an odd sort of way that will alter flow and grinder setting. Might be worth trying a couple of sharp tap downs.

If you grind as @Rob1 suggests this usually results in more compacted grinds coming out of the grinder and a lower heap. Weighing in tends to make them fluffy, how much depends on the grinder. The tapping down should help with that.

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18 hours ago, Rob1 said:

You can increase dose or grind finer. If you're single dosing the Mignon then try running with the hopper full and you'll find you don't need to have the grinder adjusted so fine. You can also increase the output. 

Good point, Rob! I was single dosing due to convenience/laziness very happily with the dark roasts. I just switched to a full hopper and the same settings gave me 16g in, 36g out in 46s... sublime to the ridiculous, but now I can so I can coarsen the over-tight grind and bring things back to a more palatable window. Yesterday was under extracted and sour, this one over extracted and bitter. The truth as always, lies somewhere between.

Thanks guys @BlackCatCoffee @ajohn for all the advice; I'd overlooked the single-dosing effect on density of the grounds. Good lesson!

 

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11 minutes ago, TimTamps said:

Good point, Rob! I was single dosing due to convenience/laziness very happily with the dark roasts. I just switched to a full hopper and the same settings gave me 16g in, 36g out in 46s... sublime to the ridiculous, but now I can so I can coarsen the over-tight grind and bring things back to a more palatable window. Yesterday was under extracted and sour, this one over extracted and bitter. The truth as always, lies somewhere between.

Thanks guys @BlackCatCoffee @ajohn for all the advice; I'd overlooked the single-dosing effect on density of the grounds. Good lesson!

 

Best to stay away from labelling shots under and over extracted , as you are not measuring them but tasting them sure itt’s bitter but at that ratio , it’s highly unlikely your shot is over extracted . 
 

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One final question; how do I compensate for the effect of the diminishing hopper - I assume I'll need to grind progressively finer as the contents reduce?

No other trick re temperature surfing which might help the extraction?

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Hopper emptying providing some beans are visible will probably be ok. Hard to say. The burrs sometime stir them up - not so good. Just find out what happens.

Temperature surfing really is more concerned with always finding the same starting conditions. Some fit a neon indicator to the heating element to see when it's on. Easiest way as they are driven by 240v as they come. They are available in a number of sizes. Some don't need that large a hole to fit one.

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Posted (edited)
1 hour ago, ajohn said:

Hopper emptying providing some beans are visible will probably be ok. Hard to say. The burrs sometime stir them up - not so good. Just find out what happens.

Temperature surfing really is more concerned with always finding the same starting conditions. Some fit a neon indicator to the heating element to see when it's on. Easiest way as they are driven by 240v as they come. They are available in a number of sizes. Some don't need that large a hole to fit one.

I'm considering adding an oversized baby's teething ring (weight 200g) to the beans in the hopper, once they get below 1/3 full (patent pending haha) to fool the Mignon into thinking there's a full hopper! It would be too large to be ground down and should provide a nice even spread of weight. result: consistent grinds! 

Hmmm wonder if it's been done...?

That's an oversized ring by the way, not an oversized baby, but I digress!

I mention this because once I get below 1/3 full, the old symptoms of single dosing return: finer and finer grind with each shot... this seems to be common experience with the Mignon.

Edited by TimTamps
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Some people use a length of perspex tube to replace the hopper. Many sizes and cut lengths available on ebay. If needed the diameter can be padded out a bit with tape. Then something to use for a weight. Loosish fitting piece of metal is the best option. Aluminium may be ideal with a length a bit over the diameter or something heavier. The length is needed to make sure it doesn't tilt too much and jam. It will need something adding to get it out when it reaches the bottom of the tube.

;) Only thing is Perspex was made by ICI who stopped making any plastics long ago but they supply a decent grade of acrylic instead. 2 or 3mm wall thickness should be fine.

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  • 2 weeks later...
On 19/04/2021 at 16:54, ajohn said:

Some people use a length of perspex tube to replace the hopper. Many sizes and cut lengths available on ebay. If needed the diameter can be padded out a bit with tape. Then something to use for a weight. Loosish fitting piece of metal is the best option. Aluminium may be ideal with a length a bit over the diameter or something heavier. The length is needed to make sure it doesn't tilt too much and jam. It will need something adding to get it out when it reaches the bottom of the tube.

;) Only thing is Perspex was made by ICI who stopped making any plastics long ago but they supply a decent grade of acrylic instead. 2 or 3mm wall thickness should be fine.

Yes, quite a few Funnel/Bellows devices on Etsy/Ebay, but in the end, square peg, round hole, literally in this case: With the frequency i change coffee, I really need to sell the Specialita and buy a Niche Zero... if I could find one!

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Mazzers work out well for weighing in when fitted with a grinds funnel. A rubber camera lens hood is good enough for the puff. The reason the funnel is best is because a brush can be used to sweep out the small amount of grinds that finish up in the channel out of the grinds chamber. Fit a spout and that can't be done. Also there may be a clump crusher arrangement and that traps grinds. This makes the Solo a bit of a pain to use - bit really being the wrong word as it causes other problems as well. Take the clump crusher out and grinds stick to the spout so on the crazy priced grinders they are held in place magnetically to make them easy to remove. That is likely to apply to any grinder with a spout.

;) So what do people do when the convert a mazzer now - buy some expensive bits to fit a spout. Might look posh etc but ...................... and maybe a super puffer helps. Small hole and bulb puffer, no chance.

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