Frequently Asked Questions
How does laser diffraction particle-size analysis compare to sieve analysis?
Greater Resolution: We are able to generate a particle-size distribution with 51 data points (size classes). Most sieve analyses use fewer than a third that many sieves.
Sub-200-micron data: Due to particle cohesion, it is nearly impossible to force dry particles through a sieve with openings smaller than ~200 microns. As a consequence, 200-micron sieves are typically the finest used in sieve analyses. So, in most sieve analyses, all particles smaller than 200 microns are classified the same, with no information about the distribution of particle sizes within that range. This makes sieving nearly useless for analyzing espresso and Turkish grinds. By contrast, we are able to provide dozens of data points within this same sub-200-micron range if the sample contains those small particles.
If laser diffraction is so good, why aren’t more people using it?
Laser diffraction particle-size analysis is commonly used in large commercial and industrial settings for determining the size of ground coffee. However, these machines are designed for high throughput in production settings rather than individual analyses in a lab. Moreover, laboratory laser diffraction particle-size analyzers are precision scientific instruments with hefty price tags, making them less common in labs offering small-quantity analyses.
You disperse samples in water. Why not analyze as a dry powder?
It is possible to disperse samples in many different fluids and use laser diffraction to analyze particle size. Both air and water are fluids, and in the eyes of Mie scattering theory, only differentiated by their refractive index. We prefer to analyze samples by dispersing them in water for a few reasons. First, to our knowledge, all coffee brewing techniques involve water, so any any effects on the grounds caused by immersing them in water are likely in line with what would occur naturally during brewing. Current research has shown that soaking grinds in water does not alter their particle size in a statistically significant way (Maille et al., 2021, Journal of Food Science), but may help liberate small sub-particles from larger ones, a process also likely to occur during brewing. Analyzing samples as a dry powder requires suspending them using high pressure jets or vortices of air. This process can lead to high-speed collisions between relatively soft coffee particles, causing them to break apart and generate new particles that were not present in the initial sample. For these reasons, we prefer to disperse samples in pure reagent-grade filtered and dionized water.
How do I interpret the cumulative distribution plot on my results PDF?
We include a plot of the cumulative distribution of particle sizes because it is both data rich and easy to extract useful data from. That being said, this type of plot is less well known than the histogram, so here is an annotated example that might help!
Are you able to analyze other particles besides coffee grounds?
Yes, we are able to process and analyze most other particulate materials that fall within the 0.5–3000 micron range. However, our workflow is optimized around coffee grounds, so if you’re interested in analyzing other particles, please contact us to confirm compatibility, pricing, and turnaround times.