A couple of weeks ago, I spent a day grinding 115 doses of donation coffee from Level Ground, measuring the density of the tamped puck using a caliper, then measuring true density using a gas pycnometer. I’ve uploaded the raw results for this experiment to GitHub. I did a similar experiment previously, but identified several… Continue reading Improved Puck Density Measurement

In my very first post, I mentioned several ways of measuring density. Since then, I’ve talked quite a bit about measuring the density of a tamped puck, but there are a few reasons I’d like to be able to measure the “true density”, i.e., the density of the beans themselves: This is something we could… Continue reading Measuring Density with Gas Pycnometry

The other day, I spent a few hours grinding coffee. In a previous post, I proposed a model of coffee grinding, along with some data from my morning coffee which seemed to support the model. However, it should be said that this isn’t very high quality data—there are very few data points outside the range… Continue reading Challenges with Density Measurement

For some time, I’ve assumed that the specific force you tamp with has little effect, as long as you tamp hard enough that the puck stops compressing. However, the results of a recent experiment led me to believe this might not be the case. To check this, I purchased a Normcore spring loaded tamper, then… Continue reading A Closer Look at Tamping

There are a few experiments I want to do which will require a more quantitative notion of grind size. To achieve this, I’ve done a few things which I’ll talk about in this post: Modify the adjustment knob to allow more precise selection Measure the change in burr spacing Measure outfall depth The Eureka Mignon… Continue reading Specialita Mods and Measurements

About six months ago, I picked up a cheap 0.01 g scale from Amazon. These go by a few names, but if your scale looks like this, then it’s probably the same scale: Over time, I’ve noticed something odd about the measurements I get from the scale. I usually weigh 18 g of beans for… Continue reading Scale Accuracy Issues

In the academic literature, several models have been proposed for extraction of soluble components from solid coffee. Some of these models are very detailed. Some use computational fluid dynamics (CFD) to model fluid flow through the packed bed in three dimensions. One of my favourite models was described by Moroney et al. in their 2019… Continue reading Modeling Extraction

I’ve watched a lot of YouTube videos on dialing in espresso. Most of them follow the same basic approach: You choose your dose based on the portafilter basket you’re using, then you adjust your grind setting so that you’re hitting a brew ratio of 1:2 in 25 to 30 seconds. For me, it always felt… Continue reading The Brewing Control Chart

There is a lot of information already out there about measuring total dissolved solids (TDS) for espresso, but I think it’s worth summarizing some of it here, to lay the groundwork for a couple of upcoming posts. When we pass water through an espresso puck, some of the coffee material is dissolved into the passing… Continue reading Measuring Total Dissolved Solids

Our previous model assumed uniformly sized particles of ground coffee. However, real coffee grounds usually have a bimodal size distribution which looks something like this: The size of the larger particles, often called “boulders”, is controlled by our grind setting. But there is also a peak on the left, corresponding with smaller particles called “fines”.… Continue reading An Improved Model of Grinding