The common advice says to grind your coffee blend into powder for instant coffee. The coffee industry does the opposite, and the reason matters.
Commercial instant extraction runs on a coarse grind of 1.5 to 3.0 mm, according to Coffee: Technology, the standard industry reference by R.J. Clarke and R. Macrae. At home, the answer is usually finer, because you strain a brew by hand instead of pushing water through a pressurized column.
The right grind depends on which kind of instant coffee you mean. This page answers both, then gets into how blends change the plan.
Two Kinds of Instant Coffee, Two Grinds
Instant coffee means one thing in a factory and a different thing in your kitchen. The grind follows the setting.
In commercial production, whole beans are extracted in percolation columns, then the brew is dried into powder. At home, you brew a strong concentrate that you can spoon into water or dry later.
Grind coarse for the first and fine to medium for the second. Filtration is what decides it.
Use the table below to pick a starting grind for the kind of instant coffee you are making.
| Your setup | Starting grind | Texture cue | Why it works |
| Factory-style extraction column | Coarse, 1.5 to 3.0 mm | Coarse sea salt | Water flows evenly, fines stay low |
| Home hot extract, paper filter | Medium-fine to fine | Table salt | More surface area, filter catches fines |
| Home cold or hot concentrate, cloth or mesh | Medium-coarse to coarse | Rough sand | Strains clean with little sludge |
| Aroma microgrounds in soluble powder | Ultra-fine, under 25 microns | Flour | Adds aroma after extraction, never before it |
The texture cues are general reference points, not exact measurements. The millimeter and micron figures come from the industry sources cited below.
Grind is only one part of the process. Roast level, extraction temperature, and drying method shape instant coffee too, but grind and filtration are the two you control at home.
Why Extraction Columns Want Coarse Grounds
In percolation extraction, roasted beans are cracked to a coarse size instead of ground fine. Fines are treated as a defect at this stage.
Finer grounds do expose more surface area, and water does pull flavor from them faster. That is the true part of the old “grind fine for strength” rule.
The problem is flow. A percolation column pushes hot water through a deep bed of grounds under pressure.
According to Clarke and Macrae, fine grinding in these beds creates high hydraulic pressure drops, which cause compacting, channeling, and poor solid-liquid contact. A coarse 1.5 to 3.0 mm grind keeps the bed open and the extraction even.
Ultra-fine particles do have a place, but it comes after extraction. According to an Elsevier handbook on soluble coffee technology, modern formulas stir an unextracted micro-fraction into the concentrated coffee liquor before drying.
That micro-fraction is ground cryogenically to under 25 microns, fine as flour. Those bits carry aroma, and they never have to survive a filter.
So the “grind like flour” rule mixes up two stages. The powder in your jar is fine because it was dried that way, not because the beans were ground that way.
Blends add one more layer, because two bean types do not fracture the same way in a grinder.
How Blends Change the Grinding Plan
Instant coffee blends usually pair Robusta for body and yield with Arabica for aroma. Those two species do not mill the same way.
The same Elsevier handbook notes that cellular structure differs between Coffea canephora, or Robusta, and Coffea arabica. Each bean needs different shear during milling.
Roast level matters just as much. Darker roasts are more brittle, so they crack into fines faster than light roasts do.
Fines are the dusty particles that hurt extraction the most. They pack the bed, encourage channeling, and leave harsh flavors behind.
The practical fix for a blend is to grind each part on its own, then mix the grounds. Do this any time the beans differ a lot in roast level or density.
A burr grinder gives you the control for that. The Baratza Encore is one example of a burr grinder with numbered, repeatable settings.
Baratza Encore: Key Specifications
- 40 numbered grind settings
- Conical burr design for even particles
- Settings run from coarse through fine
A blade grinder is a poor match for this job. It smashes beans unevenly and produces extra fines, which is the opposite of what you want.
To practice, start with a fresh whole-bean blend at a medium roast. Medium splits the difference between body and aroma for a first batch.
If you have not settled on beans yet, start with choosing a blend for instant coffee that fits your grinder and budget. Roast level then shapes the flavor you extract, so pair it with picking the right roast for an instant blend.
Troubleshooting: Weak, Bitter, or Muddy Extract
A weak, thin extract can indicate the water moved past the grounds too fast. Grind slightly finer and run another small test.
Bitter, muddy, or slow-straining extract can indicate too many fines packed in the bed. Grind slightly coarser, or switch to a paper filter if you were using cloth.
Change one variable at a time so you know what worked. Grind size is the first thing to touch, since it drives surface area and flow together.
If the taste stays flat no matter the grind, the beans may have gone stale. Check keeping an instant coffee blend fresh before you keep chasing settings.
A Simple Home Method for Instant-Style Blend Coffee
Start at medium-fine if you strain through paper, or medium-coarse for cloth and mesh. Steep the grounds in hot water, using more coffee than a normal cup would call for.
Strain the liquid twice, once coarse and once through a nut milk bag or fine cloth. The second pass catches most of the fines.
Simmer the strained liquid gently until it thickens into a concentrate, then store it cold. Spoon it into hot water whenever you want a fast cup.
A small digital scale keeps your coffee amount steady while you adjust only the grind. That makes your taste tests easier to read.
You can also freeze the concentrate in small cubes for spoon-and-go speed. Once the method is steady, the grind becomes the only dial you need to turn.
For factory-style extraction, grind blends coarse, about 1.5 to 3.0 mm, because fine grounds choke the bed. For a home concentrate, start at medium-fine and adjust.
Your next step: brew one small test batch today, taste it, and move slightly finer or coarser for the next one.