Methods
The particle-size distribution of your coffee grounds is determined using the following methods:
Sample Preparation
Once received at the lab, samples are subsampled using a cone-and-quarter technique and/or a micro riffle splitter depending on initial sample mass. Samples are then dispersed in reagent-grade water (0.2μm filtered, deionized) before being introduced into the sample cell of the laser diffraction particle size analyzer.
Laser Diffraction Particle-Size Analysis
Samples are introduced into the sample cell of Shimadzu SALD-3101 laser diffraction particle size analyzer, and dispersed using a reciprocating mixing arm. Coffee particles in the sample cell cause light from the 690-nm laser to scatter. The pattern of scattered light is measured on 76-element annular detector and related to particle size using Mie scattering theory.
Data Processing
Determination of raw particle-size data is accomplished using the Shimadzu Wing-SALD software suite. Particle sizes are reported in 51 size classes as a volume percent of the total sample.
Results Presentation
Results are delivered as a publication-quality PDF. Sample statistics (dust fraction, percentiles, median) are included along side a cumulative distribution curve and a histogram showing the entire particle-size distribution between 0.5 and 3000 microns. Determining what portion of you grounds are larger or smaller than a given size is easy using the cumulative distribution, while the histogram highlights the shape of the distribution (i.e., unimodal, bimodal). In addition to the Results PDF, the data points that define the particle-size distribution are provided as a spreadsheet (.csv format) that can be opened in any data-analysis software, including Microsoft Excel.