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.