Tamper base shape…

I’m currently mulling-over the best shape for a replacement base for my RB tamper, to use with our new 53mm baskets. Previously, I was using a 57.9mm American curve base, which I always found to work well. I don’t have much experience with flats, and as our old machine treated pucks so horrendously, it’s difficult to gauge whether it was an advantage over a flat or not. I used the base on the (arguable) logic that this very subtle convex shape can (possibly) both help to distribute the pressure from the water outwards slightly from the middle to aid puck adhesion at the sides of the basket, and to compensate for any slightly off-level tamps (the surface might be more consistent as a curve, even if the tamp is 1mm off level, whereas with a flat, even a slightly off level tamp could have a more pronounced effect).

But now I have moved to a different basket diameter and puck shape (and a resultingly often restricted headspace), I want to reassess the issue before placing my order! So, as well as reading about tamper base shapes, I’m eagerly watching the resluts of the cafe’s new flat tamper, on the new machine, with the new (and oh so intriguing) bottomless p/f! But as everything is new and unusual, and working in such lovely top notch ways, it’s tricky to judge sensibly what comparative effects such a small detail would have overall… But as ever, I’m keen to try to make the right choice!

Whilst both flat and American curves have theoretical reasoning behind them that makes sense, the ‘Euro’ curve just seems a bit crazy for me. ‘C flats’ seem odd too. As far as I can tell through research, and working it out in my head, these are the main (suggested) pro’s and con’s, for this particular scenario:

US curve Pro’s:

Shape causes the water pressure to create a stronger seal between the puck and the basket, at edges.

Shape helps to compensate for slightly off level tamps (who’s never guilty?!)

Grinders tend to dose in (roughly) a central pile. This is difficult to reverse, even with tapping to settle, etc. This base shape may help to redress this center biased distribution, by gently pushing grounds a little outwards, as well as downwards, creating a more even density of grounds throughout the puck.

This slight convex dip in the case of 53mm’s might be crucial to help avoid screw damage to the surface of the puck. The screen screw in this case protrudes about 3-4mm. Whilst completely clearing this with a flat might give the most ideal headspace, if you’re updosing, the screw will begin to dig into your puck surface by 1mm or so, which seems to be a perfect excuse for the water to start trying to channel in the center. The US curve might just help to avoid the screw penetrating the surface – OK there’s a shallow dip, but at least it’s not a hole! 

Con’s:

The dip created might lead to pooling and/or channeling through the center, and uneven extraction.

If grounds are piled in a cone, the US curve might accentuate the uneven density of the grounds; creating even more tightly packed grounds in the center, and even less well packed grounds where they are thinnest, at the sides, again leading to uneven extraction, fracturing, and channeling. 

Flat base Pro’s:

Flat screen; flat basket base; straight-sided basket; and deeper, narrow puck; logically = flat tamper/puck surface.

Especially if your headspace is restricted (to 1-4mm), having a perfectly level gap between the screen and the surface of the puck might be crucial for even water entry and extraction.

Even if grounds are piled in a roughly cone-shaped pile, a flat base might at least not further accentuate this uneven distribution.

Con’s:

…Deducible from the points listed above.

      ====================

I have to say, I might be leaning towards flat, at present, for this situation. The provided flat tamper is doing great things, and with an even more snugly fitting replacement base of my own at 53.2mm diameter, to really neatly tamp (I don’t tap the side of the basket anymore, and prefer the idea of a well-fitting tamper), it might do even greater things. Initial naked extractions are starting pretty evenly, then forming an initial 2-3 streams (in a quite even triangle around the center), which then merge into a central cone. This seems pretty ideal (apart from occasional spurts, signs of slight channeling, and slightly off center cones, all of which might be avoided by tweaking technique, grinding, dosing, and distribution ) – so I’m thinking if it ain’t broke… But then, what about that screw hole?!

As ever, there’s no hard and fast truth, especially without carrying out a lot of comparative tests! I guess it would be interesting to order a US curve, and test it against the (albeit slightly less snug) house flat, but I don’t fancy wasting £30 if it’s not as good! A bit more watching of the naked results, then I’ll decide. The effects will probably be pretty minimal either way, but it’s still quite an interesting topic, all the same. I think improving grind quality/distribution in the near future will have a bigger impact..!

http://txcp.wordpress.com/2008/05/14/what-are-your-tamper-preferences/

http://www.home-barista.com/tips/flat-or-curved-tamper-base-t7752.html

http://espressorun.blogspot.com/2007/10/tamper-base-diameter-test.html

http://www.toomuchcoffee.com/index.php?name=PNphpBB2&file=viewtopic&t=3901&postdays=0&postorder=asc&start=15

Advertisements

2 Responses to “Tamper base shape…”

  1. blackmountainscoffee Says:

    Do you all use the same tamper?
    The reason why I ask is that there are an array of different handles for tampers and I find that I produce a more consistent tamp if I find the handle more comfortable.

    • thebeanvagrant Says:

      Everyone mostly used to borrow mine when they worked with me, but now they will mostly use the supplied (and rather nice) flat 53mm, whilst I keep my new RB (whatever spec it might be) mainly to myself (my prrecious!). Found it comfy before and think the handle’s good for me.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s


%d bloggers like this: