Sunday, 8 March 2009

Grinders: blade & burr

This is a bit of a pedantic rant, but I am sick of people proclaiming that blade grinders are no good because they cut the beans and burr grinders are good because they grind the coffee.

Blade grinders have 'blades' but if you feel them you will notice they are not sharp.  They don't cut the coffee, they simply 'smash' the beans.  As a result the 'grinds' it produces are a vast array of sizes, and equally importantly, shapes.  Hopeless for espresso as the water simply takes the coarse of least resistance through the puck of coffee and it produces a curious mix of over & under extracted coffee.  Not nice.

Entry level burr grinders don't do a whole lot better either, some of them having plastic/composite burrs which wear smooth fairly quickly, unsurprisingly.

Good burr grinders, i.e. those selling for GBP200 and above in the UK actually have burrs that are quite sharp.  As a result they do 'cut' the coffee bean.  The correct term is probably 'mill'.  These sharp burrs, or teeth if you like, ensure the resulting grinds are very uniform in both size and shape.  This is what you are paying for in a top quality grinder.

The need to minimise the heating of the coffee if you are grinding any volume is addressed in three ways; 1) the use of highly conductive material (metal/metal alloy/ceramic) for the burrs to dissipate the heat away 2) larger diameter burrs so the working surface of the burr is increased, thereby spreading the thermal load over a wider area 3) reducing the revolutions at which the burr turns, which in turn requires gearing and usually a more powerful electric motor, all of which add to the cost.

All of the above needs to be mounted into a very rigid assembly otherwise the burrs would be able to flex/move as the resistance of beans stuck the working face of the burrs.  This obviously adds to the cost as robust engineering as described above is needed.  It demands high quality metals/metal alloys and plenty of them.

The upside is you aren't buying what I like to refer to as 'consumer grade junk'.  When the burrs eventually wear out in a high quality grinder (stated as every 400Kg in a Mazzer Super Jolly) you can simply replace the burrs and you have a new grinder essentially.  If you are bothered by such things this is the world our grandparents knew and it is a lot more environmentally friendly than throwing cheap, poorly made items out every year or so.

2 comments:

Ian Kynnersley said...

Hi
You mention that making coffee needn't be expensive or exclusive but you here suggest that a worthwhile coffee grinder is going to cost at least £200!

What's your take on hand-powered grinders for home use? I have a fairly cheap one but it seems to do a wonderful job and has revolutionised the quality of my filter coffee!

Ian

Reiss Gunson said...

Ian

Thanks for the comment & apologies for the delayed response.

My comments on grinders relate to espresso. Hand powered grinders are fine for filter coffee & I have one myself which I take camping.

Any grinder will revolutionise your coffee drinking experience if you have never had freshly ground coffee before (i include blade grinders in that assessment).

Grinders for espresso are another matter & unfortunately even at the £150 mark you don't really get the quality required (trust me I have bought a pile of grinders with my own coin to evaluate for sale & discarded them all and given up), not helped by the weak sterling which has driven the prices up another notch.

I guess all we are saying is there is a valid reason why good espresso grinders cost a lot; it isnt simply marketing hype. They have a tough job to do, having to grind the beans not only fine, but also ensuring that all the grinds are as close to the same size and shape as possible.

We recognise that many people are not able or indeed interested in making that kind of investment to access good espresso.

For this reason we offer the starter kit to introduce people to freshly ground filter coffee.

If you are currently using a paper filter you can take you coffee drinking experience up another significant notch with a permanent Swissgold filter.

A paper filter holds back a lot of the lipids that carry much of the taste in coffee & you will also detect a 'paper' taste in coffee that has been prepared with a paper filter.

I guess all we are trying to do is make people aware that purchasing an entry level espresso machine is guaranteed to disappoint & you are much smarter to put the money towards a better engineered model.

It also never ceases to amaze me how many people I know that have spent a lot of money on an espresso machine, yet do not own a grinder & continue to use pre-ground coffee.

It's a joke!

Cheers

Reiss