Toddy Cold Brew System

The Toddy Cold Brew System was invented by Todd Simpson, a chemical engineering graduate, in 1964. Inspired by a Peruvian cold brew method he encountered, Simpson developed a system that used a felt filter and a steeping vessel to produce smooth, low-acidity coffee concentrate. The Toddy system gained popularity in the 1980s and 1990s as cafes began offering cold brew. The system became the industry standard for commercial cold brew production and is used by major coffee chains including Starbucks. The Toddy company has since expanded its product line to include commercial-scale systems, but the original home brewer remains largely unchanged in design.

Todd Simpson (1964)

The Toddy system consists of a brewing vessel (typically plastic or glass), a rubber stopper, a felt filter, and a glass decanter. Coarsely ground coffee is placed in the brewing vessel. Cold or room-temperature water is poured over the coffee, and the mixture steeps for 12 to 24 hours. During steeping, the water slowly extracts soluble compounds from the coffee at a low temperature, producing a <a href="/coffee-encyclopedia/cold-brew-coffee-ratio-guide">concentrate</a> with lower acidity and bitterness than hot-brewed coffee. After steeping, the rubber stopper is removed from the bottom of the brewing vessel, and the concentrate drains through the felt filter into the glass decanter below. The felt filter removes grounds while allowing some oils to pass through, producing a smooth, full-bodied concentrate. The concentrate is then diluted with water or milk (typically 1:1 to 1:3) for serving.

The Toddy system uses cold water immersion extraction, which differs fundamentally from hot water brewing. Cold water extracts compounds more slowly and selectively than hot water. The lower extraction temperature (room temperature, approximately 20 to 25 degrees Celsius) means fewer acidic compounds are extracted, producing a smoother, less acidic cup. Certain bitter and astringent compounds (like some tannins and chlorogenic acids) are less soluble in cold water, so they are extracted at lower concentrations. The long steeping time (12 to 24 hours) compensates for the lower temperature, ensuring sufficient extraction of desirable compounds (sugars, body-building compounds, flavor compounds). The felt filter allows some oils to pass through, contributing to the full body and smooth mouthfeel characteristic of cold brew. The result is a concentrate that is smooth, sweet, low in acidity, and full-bodied.

Use filtered water with a TDS of 75 to 150 ppm. Cold brew is more forgiving of water chemistry than hot brewing because the long steeping time provides ample extraction regardless of mineral content. However, good water still produces better results. Aim for general hardness of 50 to 100 ppm and alkalinity of 30 to 50 ppm. Avoid very hard water, which can produce a chalky taste in cold brew. Soft water is less problematic for cold brew than hot brewing.

During steeping, water and coffee sit together in the brewing vessel with no flow (immersion). After steeping, the rubber stopper is removed from the bottom of the vessel, and the concentrate drains through the felt filter by gravity into the decanter below. The flow rate through the felt filter is moderate, and the filter retains the grounds while allowing some oils to pass through.

Typical Extraction Yield: 18 to 22% (of the coffee's soluble compounds)

Typical Strength (TDS): 3 to 5% TDS (concentrate, diluted to 1.2 to 1.5% TDS before serving)

• •Using a grind that is too fine, which produces a cloudy concentrate and can clog the felt filter
• •Not using enough coffee, which produces a weak concentrate
• •Steeping for too short a time, which produces an under-extracted, weak concentrate
• •Steeping for too long (beyond 24 hours), which can produce over-extracted, woody flavors
• •Not saturating all the grounds at the start, which produces uneven extraction
• •Not diluting the concentrate before serving, which is too strong for most people
• •Not cleaning the felt filter properly, which can cause off-flavors and clogging
• •Using hot water instead of cold, which changes the extraction profile entirely

• •Use a very coarse grind to minimize fines and ensure smooth, clean filtration
• •Stir the coffee and water thoroughly at the start to ensure even saturation
• •Use a 1:5 to 1:6 ratio for a standard-strength concentrate
• •Steep for 16 to 18 hours at room temperature, or 24 hours in the refrigerator
• •Dilute the concentrate 1:1 to 1:3 with water or milk, depending on desired strength
• •The concentrate keeps for up to 2 weeks in the refrigerator
• •Clean the felt filter by rinsing with water (no soap) and storing in a container of water in the refrigerator
• •Use the concentrate for iced coffee, hot coffee (dilute with hot water), or as a base for coffee cocktails

• •Temperature profiling: comparing room-temperature steeping vs. refrigerator steeping
• •Steeping time optimization: testing 12, 16, 20, and 24 hours for different flavor profiles
• •Blend creation: mixing different coffee origins or roast levels for complex cold brew
• •Nitro cold brew: infusing the diluted cold brew with nitrogen for a creamy, Guinness-like texture
• •Concentrate dilution: testing different dilution ratios for different serving styles
• •Hot bloom cold brew: briefly blooming the coffee with hot water before adding cold water for a hybrid extraction

• •Myth: Cold brew has more caffeine than hot coffee. Reality: Cold brew concentrate has more caffeine per ounce than regular coffee, but when diluted to drinking strength, the caffeine content is similar. The long steeping time does extract caffeine efficiently, but the dilution brings it to comparable levels.
• •Myth: Cold brew is always less acidic. Reality: Cold brew generally has lower titratable acidity than hot-brewed coffee, but the perceived acidity depends on the coffee, roast level, and dilution. Some cold brews can still taste acidic depending on the beans.
• •Myth: The Toddy is the only way to make cold brew. Reality: Cold brew can be made with any container and filter. The Toddy system is convenient and well-designed, but a French Press, mason jar, or any vessel with a filter can produce cold brew.

After draining the concentrate, discard the grounds from the brewing vessel. Remove the felt filter and rinse it thoroughly with water (no soap). Store the felt filter in a container of water in the refrigerator between uses. Wash the brewing vessel and decanter with warm water and dish soap. Dry thoroughly before storing. Replace the felt filter every 10 to 15 batches, or when it becomes clogged or loses effectiveness.

Replace the felt filter every 10 to 15 batches or when it shows signs of wear. Check the rubber stopper for wear and replace if it becomes loose. Inspect the brewing vessel for cracks (plastic version) or chips (glass version). Store the felt filter submerged in water in the refrigerator to prevent it from drying out and developing mold. No mechanical parts to maintain.

• •Chapter 6: Brewing Methods
• •Chapter 10: Cold Brewing
• •Chapter 5: Extraction Science

• specialty coffee explained guide

• •Toddy
• •Specialty Coffee Association
• •Coffee Science Foundation