Recently, I’ve been splitting my morning coffee at various brew ratios, measuring total dissolved solids (TDS) in the first part, and using this information to explore extraction dynamics using various equipment configurations. This method has a few limitations: Splitting a couple of coffees each morning, it takes a week or so to gather data for… Continue reading Introducing Salamibot

## An Analytic Solution for Extraction

In a previous post, we looked at a numerical solution to a model of expresso extraction described by Moroney et al. in their 2019 paper. In this post, I’ll to look at an analytic solution for a simplified version of that model. You may be asking why we would want an analytic solution. Or you… Continue reading An Analytic Solution for Extraction

## A Simple Model of Extraction

A little while ago, Jonathan Gagné suggested that I should take a look at the plot of extraction yield (EY) vs. brew ratio. His hypothesis was that we could fit a particular curve to the data in this plot which would give some insight into the extraction process. The model When we think in very… Continue reading A Simple Model of Extraction

## Improved Puck Density Measurement

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

## Measuring Density with Gas Pycnometry

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

## Challenges with Density Measurement

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

## A Closer Look at Tamping

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

## Specialita Mods and Measurements

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

## Scale Accuracy Issues

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

## Modeling Extraction

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