Brewing Fundamentals

Grain-to-glass process overview, core brewing metrics, and the most impactful process controls

The Grain-to-Glass Process

All-grain brewing follows a defined sequence. Understanding each stage helps you troubleshoot problems and make informed recipe decisions.

1. Milling

Crushed malt — collectively called the grist — exposes starch granules for enzymatic conversion in the mash. The grind should be coarse enough to keep husks largely intact (for wort filtration) while crushing the endosperm. A gap setting of roughly 0.9–1.1 mm is typical for a two-roll mill, though optimal crush depends on your mill and grain moisture content.

2. Mashing

The mash is the controlled steeping of the grist in hot water. Amylase enzymes — primarily alpha-amylase and beta-amylase — break down starch into fermentable and non-fermentable sugars.

Enzyme activity ranges:

Enzyme	Peak Range	Effect
Beta-amylase	60–65 °C (140–149 °F)	Produces fermentable maltose; thinner, drier beer
Alpha-amylase	68–72 °C (154–162 °F)	Produces longer dextrins; fuller body, higher FG

In practice most single-infusion mashes target 64–69 °C (147–156 °F) to balance fermentability and body. Beta-amylase denatures relatively quickly as mash temperatures move into the low 70s °C, while alpha-amylase remains active longer but also declines near mash-out temperatures. Typical mash time is 45–60 minutes for well-modified modern malt.

Mash pH (measured at room temperature) should fall between 5.2–5.6 for optimal enzyme activity, wort quality, and yeast health. This is covered in detail in Water Chemistry.

3. Lautering and Sparging

Lautering separates sweet wort from the grain bed. The first cloudy runnings may be recirculated (Vorlauf) until the wort clears. After collecting the first runnings, the grain bed is rinsed with hot water (sparging) to recover residual sugars.

Common sparging methods:

• Fly sparge: Continuous slow rinse of the grain bed while simultaneously draining — maximizes efficiency but requires careful management.

• Batch sparge: Drain, add all sparge water at once, stir, rest briefly, drain again — faster and simpler, slightly less efficient.

• No-sparge: Collect all wort from the initial mash volume; uses more grain but simplifies the process.

Sparge water temperature is typically 75–77 °C (167–170 °F). Keep grain-bed temperature and runoff pH in range during sparging to limit tannin extraction and astringency.

4. The Boil

The wort boil (typically 60–90 minutes) achieves several goals:

• Sanitation: Eliminates unwanted microorganisms.

• Hop utilization: Isomerization of alpha acids from hops gives IBU bitterness (requires sustained boiling).

• Protein coagulation: Hot break removes haze-forming proteins and precipitates as trub.

• DMS (dimethyl sulfide) evaporation: Drives off precursors of cooked-corn off-flavors from lighter malts — requires an open, vigorous, uncovered boil.

• Concentration: Evaporates water to reach target pre-boil volume and OG.

5. Whirlpool and Chilling

After the boil, a whirlpool rotates the wort to collect trub in a central cone. Hops added at flameout or during a hot-side hop stand (typically 79–88 °C / 174–190 °F) extract aroma compounds and some additional bitterness.

The wort is then chilled to pitching temperature — typically 18–20 °C (64–68 °F) for ales, 8–12 °C (46–54 °F) for lagers.

6. Fermentation

Pitching yeast into chilled wort begins fermentation. Yeast converts fermentable sugars into alcohol and CO₂ while producing flavor compounds (esters, fusel alcohols, organic acids). Krausen — a foamy head — forms during peak activity.

Primary fermentation lasts from a few days to two weeks depending on yeast strain, pitch rate, and temperature. For most ale strains this is complete when gravity stabilizes and Krausen drops.

Conditioning follows: the beer clears, off-flavor precursors (including diacetyl) are reabsorbed or metabolized, and flavors integrate. This can occur in the primary vessel or after transfer.

7. Packaging

Beer is packaged by bottling or kegging. Priming sugar added at bottling enables bottle conditioning (natural carbonation). Kegged beer is force-carbonated with CO₂. Oxygen exposure at this stage is the primary driver of staling — minimize it.

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Core Brewing Metrics

Original Gravity (OG) and Final Gravity (FG)

Gravity measures wort or beer density relative to pure water (density = 1.000 SG). OG is the wort density before fermentation; FG is the density after fermentation is complete.

• OG of most beers falls between 1.030 (light session) and 1.120 (strong ales/barleywines).

• FG typically falls between 1.006 and 1.025, depending on yeast strain and fermentability.

• Both can also be expressed on the Plato scale (°P), where 1 °P ≈ 1.004 SG.

ABV (Alcohol by Volume)

The simplified formula used by most homebrewing software:

ABV = (OG − FG) × 131.25

A more accurate version (Balling formula, used by Brewfather):

ABV = (76.08 × (OG − FG) / (1.775 − OG)) × (FG / 0.794)

The simplified formula is accurate to within ~0.1–0.2% ABV for most standard-gravity beers. The Balling-derived formula is more accurate at higher gravities.

Attenuation

Attenuation measures how much of the wort's fermentable sugar was consumed. Apparent attenuation (the most commonly reported value) is:

Apparent Attenuation (%) = (OG − FG) / (OG − 1.000) × 100

Example: OG 1.050, FG 1.010 → attenuation = (0.040 / 0.050) × 100 = 80%

Typical attenuation ranges:

• Low-attenuation strains: 65–72 %

• Mid-attenuation strains: 73–79 %

• High-attenuation strains: 80–85 %+

Apparent attenuation overstates true (real) attenuation because alcohol is less dense than water, making the final beer appear lighter than it is.

IBU (International Bitterness Units)

IBU measures the concentration of isomerized alpha acids in finished beer (mg/L or ppm). In practice, perceived bitterness depends on IBU relative to residual sweetness — the bitterness:gravity ratio matters as much as raw IBU.

BU:GU (Bitterness:Gravity Ratio) = IBU / Gravity Units

where Gravity Units (GU) = (OG − 1.000) × 1000

• Below 0.5: Decidedly malty

• 0.5–0.8: Balanced

• Above 1.0: Decisively bitter

Common IBU calculation models:

• Tinseth (default in Brewfather): Accounts for pellet utilization and wort gravity.

• Rager: Tends to predict higher utilization at longer boil times.

• Garetz: More conservative; accounts for hop storage degradation.

No model is perfectly accurate; treat IBU values as estimates and calibrate against your palate.

SRM and EBC (Beer Color)

SRM (Standard Reference Method) and EBC (European Brewery Convention) both quantify beer color.

Conversion: EBC ≈ SRM × 1.97

SRM is calculated using the Morey formula from Malt Color Units (MCU):

SRM = 1.4922 × MCU^0.6859 where MCU = (grain weight in pounds × grain color in °L) / wort volume in gallons

Rough color reference:

SRM	Description	Typical Style
2–4	Pale straw	Pilsner, Cream Ale
5–9	Gold	Pale Ale, Kölsch
10–17	Amber	Amber Ale, Vienna Lager
18–26	Brown	Brown Ale, Altbier
27–35	Dark brown	Porter
35+	Black	Stout

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Process Control Priorities

Not all brewing variables are equally impactful. Focus here first:

1. Sanitation: Any contamination before fermentation can ruin a batch. Clean thoroughly, then sanitize contact surfaces with a no-rinse sanitizer (e.g., Star San, Iodophor).

2. Temperature control during fermentation: Off-flavors (excess esters, fusel alcohols) are strongly driven by fermentation temperature. Even ±2 °C (4 °F) above the optimal range noticeably affects some strains.

3. Yeast pitch rate: Underpitching stresses yeast, producing off-flavors and increasing attenuation variability. Match pitch rate to wort OG, volume, and yeast viability.

4. Mash temperature and pH: Determines fermentability (OG→FG ratio) and wort flavor baseline.

5. Oxygen management: Critical on the cold side (post-fermentation). Pre-boil oxygenation of wort actually helps yeast; post-fermentation exposure stales beer rapidly.

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Common Beginner Mistakes

Mistake	Effect	Fix
Underpitching yeast	Slow start, off-flavors, incomplete attenuation	Use a pitch rate calculator; make a starter for high-gravity beers
Fermenting too warm	Excess esters, fusel alcohols	Control temperature; pitch at the low end of the yeast's range
Skipping mash pH	Under/over-extraction, harsh or thin wort	Aim for 5.2–5.6 pH; adjust water chemistry or use acid
Opening fermenter early	Oxygen exposure, potential contamination	Trust gravity readings over visual activity
Incorrect equipment profile	All recipe estimates are wrong	Set up equipment profile accurately before brewing
Not cold-crashing	Hazy beer and more yeast in package	Cold crash 24–48 h before packaging
Rushing conditioning	Incomplete diacetyl cleanup, green flavors	Allow at least a diacetyl rest for ale strains; lagers need longer conditioning

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Brewfather Tip

Setting up your Equipment Profile is the single most important step in Brewfather. Every recipe metric — OG, volume, efficiency, hop utilization — is calculated relative to your equipment. Before brewing your first recipe:

1. Go to Profiles → Equipment and create a profile for your system.

2. Enter measured values for mash tun dead space, boil-off rate, fermenter losses, and trub/chiller losses.

3. Set your brewhouse efficiency (start at 72% if you don't have data; dial it in after a few batches).

After each brew, record your measured OG, pre-boil gravity, and actual volumes. Brewfather's batch screen lets you log these against predictions — over time your calibrated profile makes recipe estimates highly accurate.

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Sources

• Palmer, John J. How to Brew, 4th ed. Brewers Publications, 2017. (Chapters 2–7, enzyme temperatures, attenuation, ABV formula)

• Daniels, Ray. Designing Great Beers. Brewers Publications, 1996. (IBU models, color calculations)

• Fix, George. Principles of Brewing Science, 2nd ed. Brewers Publications, 1999. (Enzyme kinetics, mash chemistry)

• Tinseth, Glenn. "Glenn's Hop Utilization Numbers." Real Beer Page. (IBU Tinseth model)

• Brewfather Docs. "Relative Bitterness Ratio." (BU:GU gravity-unit definition and Brewfather implementation)

• Morey, Daniel. "Approximating SRM Beer Color of Homebrew." (Morey SRM formula)

• Kunze, Wolfgang. Technology Brewing and Malting, 5th ed. VLB Berlin, 2014. (Balling formula, lautering)