What is a grindometer used for in chocolate making?

A grindometer measures maximum particle size in chocolate mass. You pull a warm chocolate sample across a machined groove that tapers from 100 microns to 0; where the surface becomes rough indicates maximum particle size. For craft chocolate, you are targeting readings of 10–20 microns. This tells you when to stop the melanger rather than relying on time alone.

What particle size should chocolate be?

The optimal range for craft chocolate is 10–20 microns. Human tasters detect grittiness above approximately 30 microns. Industrial targets are 18–25 microns D90. Over-refining below about 5 microns makes chocolate taste gummy. The grindometer reading at the transition point tells you the worst-case (largest) particle size in your batch.

How do I use a grindometer correctly?

Place warm, fluid chocolate at the deep end of the groove. Draw the steel scraper from deep to shallow in one smooth, continuous motion. Immediately observe where the surface becomes rough — that transition point is your maximum particle size reading. The chocolate must be warm enough to flow into the groove; cold chocolate gives inaccurate results.

When should I check particle size during a melanger run?

Check at 6, 12, 18, and 24 hours for your first batches to build a refining curve for your specific machine and origin combination. Above 40 microns means continue. The 20–25 micron range means approaching target. The 10–20 micron range is the stop point unless continuing for additional conching flavor development.

Can I tell particle size without a grindometer?

The only reliable method without a grindometer is tasting, but taste testing is subjective and detects grittiness only after the fact. Time is a rough proxy — most batches reach target particle size in 18–30 hours — but refining speed varies by origin fat content and formulation. A grindometer replaces guesswork with objective measurement.

What does it mean if my grindometer reads consistently below 10 microns?

Below 10 microns indicates over-refining. Chocolate refined to this level begins to taste gummy because the extremely small particles create a different mouthfeel than the optimal 10–20 micron range. If you consistently see sub-10 micron readings, stop the melanger earlier in future batches.

How to Measure Chocolate Particle Size: Grindometer Guide

A TQC grindometer is a flat steel block with a machined groove that tapers from a known depth (typically 50 or 100 microns) to zero. You pull a small sample of chocolate across the groove; where the surface becomes rough tells you your maximum particle size. For craft chocolate, you are targeting readings below 20 to 25 microns. Without this tool, you are guessing when to stop the melanger.

Why Particle Size Matters

Human tasters cannot detect grittiness below approximately 30 microns. Dandelion Chocolate specifies a range of 20 to 35 microns as the detection threshold, with the tighter Beckett Science reference giving approximately 30 microns. Optimal chocolate falls in the 10 to 20 micron range — Dandelion’s target for finished bars. Industrial standard is 18 to 25 microns D90.

Over-refining below approximately 5 microns makes chocolate taste gummy, not smooth. There is a specific quality sweet spot between 10 and 25 microns where chocolate is smooth without being over-processed.

Particle size distribution matters beyond the mean. The goal is a tight distribution where 90% of particles fall within the 10 to 20 micron range, not a mean of 15 microns with a wide tail of larger particles. The grindometer measures maximum particle size — it is telling you the worst-case end of your distribution, which is the end that causes grittiness.

What a Grindometer Is

The TQC grindometer (also called a Hegman grindometer or fineness of grind gauge) is a precision measurement tool that originated in the paint and coatings industry. In that context, it measures pigment particle size in dispersion. Chocolate makers repurposed it for measuring cocoa and sugar particle size in chocolate mass.

The tool is a steel or stainless steel block, typically 25 cm long, with one or two parallel grooves machined to precise depths. A single-groove gauge for chocolate typically runs from 100 microns at the deep end to 0 at the shallow end. The deep end is marked with the micron scale.

TQC Grindometer 0-100 Micron

The Measurement Technique

This is the core of the grindometer method:

Bring a small sample of chocolate (approximately 0.5 to 1 gram) to the deep end of the groove. The chocolate should be warm enough to be fluid — above approximately 40°C or 104°F. Cold or semi-solid chocolate will not flow into the groove correctly.
Place the provided steel scraper perpendicular to the groove at the deep end.
In one smooth, continuous motion, draw the scraper from the deep end to the shallow end (from 100 microns toward 0). Apply enough pressure to keep the chocolate in the groove.
Immediately observe where the surface becomes rough or shows distinct particle marks. This transition point corresponds to the maximum particle size of your sample.
Read the micron number at that transition point.

A reading of 25 microns means your largest particles are at or near 25 microns. A reading of 40 microns means you have particles in the 40-micron range that need more refining.

What Readings Tell You About Your Batch

Above 40 microns: Still in early refining. The mass may still be chunky and not fully homogenized. Let the melanger run and check again in 4 to 6 hours.

25 to 40 microns: Making progress but below the smooth threshold. This is typical at 8 to 12 hours in a melanger. Continue running.

20 to 25 microns: Approaching the target. The chocolate is smooth to most tasters but not at peak quality. Check again in 2 to 4 hours.

10 to 20 microns: Target range. Optimal for craft chocolate. This is when to stop unless you want to continue for flavor development in the conching phase.

Below 10 microns: Over-refined. Chocolate begins to taste gummy. If you are consistently below 10 microns, stop sooner in future batches.

Grindometer vs. Time: Which Should You Use?

Both. Use time as your rough guide and the grindometer to confirm. Different origins may refine faster or slower because fat content varies significantly — Tanzanian and Trinidadian beans at 57 to 58% fat versus Ecuadorian at approximately 52% fat (Dandelion). If your chocolate is too thick at target particle size, our viscosity troubleshooting guide covers the fixes. Higher-fat beans generally refine faster because fat acts as a lubricant.

Two-ingredient chocolate without added cocoa butter refines differently than formulations with additional cocoa butter. More fat means more lubrication, potentially faster particle reduction but also more fluid mass that may change the grinding dynamics.

Running the grindometer at 6 hours, 12 hours, 18 hours, and 24 hours for your first several batches builds a map of your specific melanger’s refining curve. Once you know that your Spectra 11 reaches target particle size at 20 hours with a specific origin, time becomes a reliable guide for that combination.

Cleaning the Grindometer

The grindometer should be cleaned immediately after each use while the chocolate is still warm. Warm chocolate wipes out easily; cooled chocolate sets in the groove and is difficult to remove without damaging the precision surface.

Clean with a dry cloth or paper towel, wiping along the groove from deep to shallow. If chocolate has hardened, warm the block slightly (warm water on the outside, not inside the groove) before wiping. Do not use abrasive materials — the machined groove surface must maintain its precision to give accurate readings.

Store the grindometer in its case, groove side protected.

Cost and Availability

TQC grindometers cost approximately $100 to $200 depending on range and material. For chocolate, a 0 to 100 micron range is appropriate. The TQC brand is the standard recommendation from both Dandelion Chocolate and Chocolate Alchemy.

At $100 to $200 for a precision instrument that replaces all guesswork about when to stop your melanger, the grindometer is among the highest-value tools in a chocolate maker’s kit.

Connecting Particle Size to Finished Quality

The grindometer tells you when your particle size is right. But particle size is only one dimension of finished chocolate quality. A batch at 15 microns after 12 hours has different flavor than the same batch at 15 microns after 30 hours — the longer batch has more conching, more volatile acid removal, and different flavor development. The grindometer answers “is the texture right?” The tasting panel answers “is the flavor right?”

Use both. The grindometer gives you the objective measurement; your palate gives you the subjective quality assessment. For the full context on how particle size connects to conching and flavor development, see our conching chocolate guide. For understanding the refining and conching process that the melanger is running, see our melanger refining guide.

Frequently Asked Questions

What is a grindometer used for in chocolate making?: A grindometer measures maximum particle size in chocolate mass. You pull a warm chocolate sample across a machined groove that tapers from 100 microns to 0; where the surface becomes rough indicates maximum particle size. For craft chocolate, you are targeting readings of 10–20 microns. This tells you when to stop the melanger rather than relying on time alone.
What particle size should chocolate be?: The optimal range for craft chocolate is 10–20 microns. Human tasters detect grittiness above approximately 30 microns. Industrial targets are 18–25 microns D90. Over-refining below about 5 microns makes chocolate taste gummy. The grindometer reading at the transition point tells you the worst-case (largest) particle size in your batch.
How do I use a grindometer correctly?: Place warm, fluid chocolate at the deep end of the groove. Draw the steel scraper from deep to shallow in one smooth, continuous motion. Immediately observe where the surface becomes rough — that transition point is your maximum particle size reading. The chocolate must be warm enough to flow into the groove; cold chocolate gives inaccurate results.
When should I check particle size during a melanger run?: Check at 6, 12, 18, and 24 hours for your first batches to build a refining curve for your specific machine and origin combination. Above 40 microns means continue. The 20–25 micron range means approaching target. The 10–20 micron range is the stop point unless continuing for additional conching flavor development.
Can I tell particle size without a grindometer?: The only reliable method without a grindometer is tasting, but taste testing is subjective and detects grittiness only after the fact. Time is a rough proxy — most batches reach target particle size in 18–30 hours — but refining speed varies by origin fat content and formulation. A grindometer replaces guesswork with objective measurement.
What does it mean if my grindometer reads consistently below 10 microns?: Below 10 microns indicates over-refining. Chocolate refined to this level begins to taste gummy because the extremely small particles create a different mouthfeel than the optimal 10–20 micron range. If you consistently see sub-10 micron readings, stop the melanger earlier in future batches.