Naked PF extraction diagnosis

[Matt_King Senior Member Find all posts View Profile Close Matt_King]

A while back I asked some questions about why my singles were pouring much more smoothly than my doubles. I got a naked PF for Christmas which showed me that the single extracts really evenly, but the double filter is starting more at the edges as a ring, and usually has a blank spot in the middle.

My tamper is nothing special, a bit undersized. I suspect that either that or my tamping technique may be contributing, with insufficient tamping at the edges of the filter.

Thoughts?

[iaindb Senior Member Find all posts View Profile Close iaindb]

Re: Naked PF extraction diagnosis

probably either grind / dose / tamp (does that narrow it down enough?!)

Do you adjust the grind for doubles vs singles? What is the shape of the bottom of your double vs single basket? Singles often have tapered bottoms, whereas doubles are often right angles.

Think of a flat roof with no supporting beams - as you pile weight on the top, it will bow toward the middle. A similar thing happens with pressing on the grinds when the bottom is flat and the top is level, which you may not see with a single because of basket shape / dose.

Try scraping the top with a circular object like your doser / hopper lid, to give a concave surface to the grinds (higher at the edges), and then tamp that.

Id be interested to see if it helps, since thats what I do with my VST, but I dont have a naked basket to see the effects

[artman Senior Member Find all posts View Profile Close artman]

Re: Naked PF extraction diagnosis

Yes, as above. Also, do you leave the grinds in a mound with a central peak and do not spread prior to tamping? This will cause the outside to not be compacted as much as the middle. If your tamper is significantly smaller than the basket, this could also lead to the donut extraction.

Try the WEISS distribution and see if it helps.

Try not to change too many things at once, so you can see how each change effects things.

Cheers

[early_morning_ Senior Member Find all posts View Profile Close early_morning_]

Re: Naked PF extraction diagnosis

most machines have a nice bit screw in the centre of the shower screen meaning that theres no water falling directly onto the centre of the puck - thats alway been my theory as to why doubles seem to start in a "doughnut" of sorts.

my guess is that because the sides are tapered and the holes are central, the single forces all the espresso out from a much smaller area which makes any sort of doughnut indistinguishable.

so long as youre not getting little pee-streams firing out of the bottom of your puck due to channel, i think youre probably doing ok.

[Matt_King Senior Member Find all posts View Profile Close Matt_King]

Re: Naked PF extraction diagnosis

The double (as opposed to the triple) has slightly tapered walls over the bottom quarter.

Dosing technique is to level off, knock down (or rest the tamper on top) fill and level off again. Might try the concave dosing method though.

The shower screen has a flat disc welded on, maybe 5mm diameter.

[iaindb Senior Member Find all posts View Profile Close iaindb]

Re: Naked PF extraction diagnosis

Dosing technique is to level off, knock down (or rest the tamper on top) fill and level off again

so thats fill-level-knock-fill-level-tamp?

instead try fill-knock*-fill-scrape**-tamp

* one gentle knock
** with circular object

be careful with the knock - doing less of it is improving my chanelling and flavour.

How far is your dose from the screen? Have you done the 5c test? If theres sufficient pressure and the puck isnt too high, the water should fill the gap, screen, and group pushing over the surface of the puck.

Got a vid on the tube yet?

[GregWormald Senior Member Find all posts View Profile Close GregWormald]

Re: Naked PF extraction diagnosis

A while back I asked some questions about why my singles were pouring much more smoothly than my doubles.  I got a naked PF for Christmas which showed me that the single extracts really evenly, but the double filter is starting more at the edges as a ring, and usually has a blank spot in the middle.

My tamper is nothing special, a bit undersized.  I suspect that either that or my tamping technique may be contributing, with insufficient tamping at the edges of the filter.

Thoughts?

Ill go with the highlights as a first guess.
Tidying your technique is always useful though.

Greg

[Inga51 Member Find all posts View Profile Close Inga51]

Re: Naked PF extraction diagnosis

so thats fill-level-knock-fill-level-tamp?

instead try fill-knock*-fill-scrape**-tamp

* one gentle knock
** with circular object

This was my thinking too. The latter is my technique, but with a bit of WDT thrown in before the knock down (to break up any clumps dosed by my doserless grinder). And as Greg pointed out, the too small tamper is potentially a major issue.

Cant wait to hear how you progress with this. Sounds like youre in for a treat when you get the doubles dialed in nicely.

Chris