What’s a Grindometer?

Along the south wall of our factory on Valencia Street, there are six, spinning steel melangers.  This is where the cocoa nibs turn into cocoa liquor, and where the liquor and sugar are refined and conched until they have reached the perfect consistency and flavor to become a chocolate bar. The melangers themselves are actually modified spice grinders from India, comprised of two spinning granite wheels and a granite base. They spin 24 hours a day, crushing nibs and sugar together and oxidizing the mixture which helps release volatile aromatics. Each batch stays in the melanger for three to five days, until we know the chocolate is ready. But how do we know when it’s ready?

Deciding when to “pull a batch” is a matter of personal judgment, but we have a few benchmarks and tools to help us. First, we taste. Is it well-balanced? Delicious? Smooth? Exactly as it should be? If we taste grit—which indicates the particle size is still too large and needs more time under the granite wheels—we know it’s not ready. If the texture is smooth but there are a few off flavors, it needs more time to conch and mellow out. If the texture and flavor are flat, it means it may have been in the melanger too long and refined to a particle size that’s too small. We prefer a particle size between 20 and 30 microns, which makes for a smooth mouthfeel but isn’t too small to keep the flavor from dancing around* in your mouth.

To help us understand what we’re tasting, we used to use something called a micrometer, which measured particle size by pinching a small sample of chocolate. This was a good tool, but it was limited to measuring only the largest particle in any given sample. Even if we measure three times, that’s only three particles.

Enter the grindometer. We learned about grindometers at last year’s Chocolate Maker Unconference, and later decided to purchase a particular model that we learned about from the guys at Hexx Chocolate in Las Vegas. A grindometer is a beautifully simple instrument used to measure particle size in suspensions, usually printing inks and paints. The instrument itself is a stainless steel brick with two almost imperceptibly shallow channels carved across the length of it. The grooves graduate from a depth of 100 micrometers below the surface to 0 micrometers (where it’s flush with the surface). To use it, we drop two small blobs of chocolate onto the top of either channel, and scrape them to the end with a straight steel scraper.

The particles slip under the scraper as the space between the scraper and the steel brick grows smaller, which means we get to see the entire distribution of particle size throughout a single sample of chocolate. Where the shade of the chocolate’s color changes most abruptly, from dark to lighter, indicates the size of the majority of the particles.

When that drop-off happens between 20 and 30 microns, we know the chocolate is somewhere close to its sweet spot, and could be ready to pull.

To see it in action, stop by the factory!

*real scientific term