Large extraction variances day to day

[Kit666]

Hi Jackstar,
Unfortunately it's not feasible for me to swap grinders with my friend temporarily.

An update for those interested.
I was determined to understand what's going on and started keeping a log of my extractions from 11/2.
I used the same technique each time, same dose, same boiler temperature, and persevered with the same grind settings until I was able to pull several consistent shots.

Some observations:
- after some initial variances I seemed to reach a level were my extractions were very consistent - after I changed beans and dialled in the grind, the inconsistencies returned.
- ambient temperature and humidity does not seem to significantly affect extraction.
- despite paying particular attention to how I handle the grinds and using a distribution tool, i consistently get channelling and spritzing.

I feel I have hit a level of consistency now with the occasional outlier which I can't explain.

I've not put around 1kg through the new burrs...
Perhaps my new burrs are starting to wear in.. but in any case I'm much happier than I was a week ago.

[Kit666]

An additional note. My friend with the same grinder changed burrs at the same time I did and he did not see the variable extractions as I did.

The only thing I can think of that may attribute to this is that he overdoses his basket, whereas I dose to basket rating (18gm VST).

I do think overdosing introduces a buffer and a greater margin of error

[Rami]

How much retention do you normally have? Do you purge?

I used to have a similar experience until I got the niche

[Kit666]

How much retention do you normally have? Do you purge?

I used to have a similar experience until I got the niche

I generally purge on the first shot of the day, subsequent shots I don't purge, even if the second shot is several hours later.
the strange thing is that if shot variance is due to technique or stale retention, you would expect that shot to be shorter; I'm finding most of my shots are reasonably consistent with an occasional outlier that is a much longer shot.

[Rami]

I generally purge on the first shot of the day, subsequent shots I don't purge, even if the second shot is several hours later.
the strange thing is that if shot variance is due to technique or stale retention, you would expect that shot to be shorter; I'm finding most of my shots are reasonably consistent with an occasional outlier that is a much longer shot.

What do you mean shorter?

[Kit666]

What do you mean shorter?

Shorter as in Underextracted

[Rami]

Shorter as in Underextracted

So you get the occasional channeling? That’s what it sounds to me

[Kit666]

Actually it's quite the opposite; despite paying a lot of attention to my technique, I consistently get channelling and some degree of spritzing. I obviously can do better otherwise it wouldn't channel all the time. Although this has me thinking about other factors...

If I was getting occasional channelling, I would expect that shot to be short.. in my case it's strange that my outlier shots are longer yet still show signs of channelling.

Some thoughts:

- is this a case of my new grinder burrs breaking in and slowly becoming more consistent?

- is it clumping of my grinds? (Which the compak K3 is known to do)

- would overdosing my basket alleviate the problem?

[Rami]

Kit666

i think channeling is when you get a weak spot in the puck where more water is forced through the channel and you end up end up with a longer shot.

not the other way around.

[Kit666]

Kit666

i think channeling is when you get a weak spot in the puck where more water is forced through the channel and you end up end up with a longer shot.

not the other way around.

Under/ Over Extraction is generally a reference of extraction yield and time.

So let's say you're pulling a 1:2 ratio from 18gms then your yield is 36gms.
Now let's factor in time; you generally target an extraction time of 25-30s as a starting point; once you reach that target, you then tweak the grind and dose to your liking (and tweak brew head temperature even)

If the time taken to extract your yield is much quicker than your target, that's known as under extraction (or quick, or short extraction).

If the time taken to extract your yield is much longer than your target, that's known as over extraction (or long).

Channelling is when the water has found a quicker path through the puck (as you mentioned, puck weakness); so in that sense, channeling will always result in under (or short) extraction.

So bringing this back to my scenario... If my inconsistencies in my extractions were due to occasional bad technique or stale grind retention, then I would expect the outlier shot to be underextracted (or short)... Instead I'm seeing outliers that are well overextracted (or long).... Unless of course I consistently have bad technique and occasionally have good technique which results in my over extracted outlier!

[Rami]

Not sure I understand with your definitions.

under extracted coffee would take more time to give me my yield.

Over extracted coffee would take much shorter time to give me my yield.

My process I keep dose constant. Then adjust grind to hit the right yield. If time is in the ball park I am done.

[Ronin]

Rami you have your under and over around the wrong way.
Under extraction is faster shots
Over extraction is slower shots