After this morning’s update I’ll stop boring you about grinder burrs (at least for the foreseeable future!).
I’ll discuss two topics about burrs and associated techniques for handling coffee grinding in the context of single dose grinders.
I’ve been remembering my experiences with new grinders and the one thing that always caused me trouble was the new burr effect. When coffee burrs are fresh, they have microscopic edges which are yet to become smooth which then result in coffee grounds that are not optimal for extraction. Depending on what you read it takes anywhere between 5 and 20 kg of coffee to go through the burrs to season them and remove that rough cutting edge. One way to short cut the process is to run par boiled rice through the grinder. You may recall that I mentioned one of the long list of grinders I’ve had on the counter, the HG one hand grinder.
In order to season that grinder I had to use carpentry clamps to secure it to our dining table and then had the most almighty work out (think sailing winch exercises). My family thought I was even more crazy than normal! The effect of running par boiled rice through the grinder was immediate and coffee shots were less bitter, more balanced, and sweeter. Your mileage may vary!
Returning to another topic that we’ve discussed before, there are particular techniques that assist with the breed of grinders known as single dose grinders. All grinders suffer from static cling. That’s as a result of the triboelectric effect… "a type of contact electrification in which certain materials become electrically charged when they are brought into contact with a different material and then separated” (source: Wikipedia). The main problem with static cling is that coffee grounds clump and become difficult to deal with in the portafilter basket. Grinder manufacturers which produce grinders that use hoppers (NOT single dose grinders) deal with static cling by introducing mechanisms such as grates in the exit path of the grinder which result in significant coffee retention (in other words stale coffee) and non-clumpy coffee. One of the things we’re trying to avoid when we use single dose grinders is retention (maximising coffee freshness and also having lots of control over dosing, with the side benefit of being able to instantly switch to a different coffee) and so we have to deal with static cling and clumps using different techniques. These techniques are well understood in the coffee industry and have fancy acronyms:
- RDT - Ross Droplet Technique (really) - a little spray of water from a stylish atomiser on your unground beans prior to introducing them to your single dose grinder tends to significantly reduce static cling; and
- WDT - Weiss Distribution Technique (again really) - stirring ground coffee in the portafilter with a mini-whisk or a tool specifically designed for the task helps to break up clumps and redistribute the coffee such that the ensuing extraction is even and wonderful. Tools that are designed for WDT tend to look like medieval torture devices… here’s one for your viewing pleasure:
When I get some time I may video the way I prepare an espresso puck so that you can see the ritual and obsession involved…
To understand the anatomy of a coffee cherry click here
To learn about the coffee taster's flavour wheel click here