Milling and the Grain Bill
Milling is the first physical step of brew day: crushing malt to expose its starchy interior so water can reach it during the mash. The crushed grain is called the grist, and its composition, the grain bill, is the malt half of Recipe Formulation.
#Why Crush at All
Whole malt kernels are sealed by a tough husk. The mash cannot extract sugar from an intact kernel; the goal of milling is to shatter the endosperm while keeping the husk intact.
- Endosperm cracked into grits and a little flour
- Husk split but left in large pieces
- Minimal pulverized dust
The husk matters because it forms the natural filter bed during Lautering and Sparging. Shred the husks and you get a stuck sparge and harsh, astringent tannins.
#The Mill Gap
Crush quality is set by the roller gap on the mill.
| Gap | Result |
|---|---|
| Too tight (<0.9 mm) | High extraction, but shredded husks, stuck mash |
| Typical (1.0–1.1 mm) | Good balance for most systems |
| Too wide (>1.3 mm) | Whole kernels, low efficiency |
Homebrewers using a mash tun with a false bottom usually run 1.0–1.1 mm. Brewers with New England IPA grists heavy in flaked adjuncts sometimes mill base malt tighter and add rice hulls for filtration.
#The IPA Grain Bill
IPA grists are intentionally pale and lean so Hops are not masked. See Base Malts and Specialty Malts and Adjuncts for detail.
| Component | Role | Notes |
|---|---|---|
| 2-row / Maris Otter | Base, 85–95% | Clean, fermentable |
| Munich / Vienna | Backbone, 0–10% | Adds malt depth |
| Light crystal | Color/sweetness, 0–6% | Use sparingly |
| Flaked oats/wheat | Body, haze, 0–20% | Key for NEIPA |
| Sugar/dextrose | Dry-out, 0–10% | Common in Double IPA |
Crushed malt stales faster than whole grain. Mill the day of brewing, or within a few days, and store airtight.
Oats and wheat have no husk. A high-adjunct NEIPA grist is prone to stuck runoff; add 3–5% rice hulls as insurance.
The grain bill, once milled, is ready for Mashing.