KULM

01What is KULM

KULM is an inverse coffee calculator. The difference with any other brewing app is substantial and worth understanding well before you start.

In conventional apps, the user enters brewing parameters — dose, water, temperature, time, grind — and the app reports what the result will be. KULM works the other way around: the user describes the coffee they want to drink, and the app calculates the exact parameters to achieve it.

Why this changes the rules

Professional baristas know the real mental process isn't "I have 18 grams and 250 ml, what comes out". It's the opposite: "I want a bright cup with medium body and present sweetness, how do I brew it?". KULM operates at that level. You start from the sensory goal and the engine translates that goal into precise brewing instructions.

This has practical implications: if one morning you want a more vibrant, acidic cup, you don't need to remember whether that means hotter water, finer grind, or tighter ratio. You just move the sensory sliders toward more acidity and KULM recalculates the whole recipe for you.

How it differs from other apps

Most coffee apps offer three things: a timer, a table of preset recipes, or a ratio calculator. KULM does none of these. It has a kinetic engine based on published scientific literature, a sensory translation layer using SCA-standardised descriptors, and automatic classification against the Brewing Control Chart standard.

We say this not to boast about technical complexity but because it affects how you should use the tool: the recipes you get have scientific grounding, but also real limitations we'll explain further on.

Philosophy

KULM is designed for the demanding barista who wants rigour without unnecessary friction. The app is 100% local, doesn't sync to the cloud, doesn't require registration, doesn't collect personal data. It works offline (except for the initial KULM Pro purchase, which Apple handles). Your history is yours and lives on your device.

02Getting started

KULM's flow is three steps in sequence. There are no hidden settings or mandatory initial configuration: you open the app and you're already on step one.

Step 1 — Choose your brewing method

KULM includes eight methods: Kalita, V60, Chemex, Aeropress, French Press, Cold Brew, Espresso and Moka. Each method has its own calibration in the engine and its own parameter ranges, because extraction in a V60 conical filter doesn't behave like total immersion in a French Press.

The free version includes the full Kalita method, with the engine and SCA classification uncut. The other seven methods require KULM Pro, explained in section 9.

Step 2 — Define your sensory profile

Here you describe the coffee you want using five sliders: acidity, body, sweetness, bitterness, and finish. Each slider has a range of 0 to 10 and affects the final recipe. Section 3 of this manual goes into detail on what each means.

You can also pick from the preset profiles KULM offers: balanced coffee, bright citric, heavy with chocolate notes, delicate floral, and others. These profiles are built using descriptors from the SCA Coffee Taster's Flavor Wheel.

Step 3 — KULM gives you the recipe

After completing the two previous steps, KULM calculates and shows the full recipe: coffee dose in grams, water in millilitres, ratio, water temperature, grind size (in SCA number) and total brewing time. It also shows the Brewing Control Chart classification.

The recipe is automatically saved to your local history if you decide to brew it. You can consult it later to repeat or tweak.

Which method to start with

If you're new to filter methods, start with V60: there's plenty of literature available, medium grind, it tolerates minor errors, and lets you perceive sensory changes clearly. If you come from espresso, start with Espresso: the engine is calibrated for the short times and concentrated ratios characteristic of the method.

The Kalita method (the only free one) is also a good starting point: flat filter, stable flow, less prone to channeling than V60.

03The sensory profile

The sensory profile is KULM's core input. This is where the inverse calculator differs from any other tool: you don't enter grams or seconds, you enter sensations.

The five dimensions of the profile are based on descriptors from the SCA Flavor Wheel and Coffee Taster's Flavor Wheel, adapted to a quantifiable model. Each dimension has a range of 0 to 10.

Acidity

Acidity is the lively, bright, sometimes citric sensation that wakes up the front of the tongue. It's not sour. It's not vinegary. It's the quality that makes an Ethiopian or a Kenya AA feel "vibrant".

What each range means

• 0-2: suppressed acidity. Flat coffee on the front. Typical of very dark roasts or stale beans.
• 3-4: mild acidity. Present but discreet. Typical of balanced blends or Brazilian naturals.
• 5-6: medium acidity. Perceivable and pleasant without dominating. Many Central American coffees sit here.
• 7-8: high acidity. Bright and marked. Washed Ethiopia, Kenya, many speciality light roasts.
• 9-10: extreme acidity. Pointed, almost piercing. Only very specific high-altitude coffees with special processing.

How it affects the recipe

More acidity in the profile typically translates in the engine as hotter water, slightly coarser grind, more open ratio, and shorter time. These are the vectors that extract chlorogenic acids first and limit the output of bitters and heavier compounds.

Body

Body is the tactile sensation of coffee in the mouth: thin like tea, round like broth, heavy like cream. It has nothing to do with flavour but with texture.

What each range means

• 0-2: very thin body. Almost watery. A V60 with low-mineralisation water and washed coffee gives bodies like this.
• 3-4: light body. Like a good oolong tea. Typical of fine filters.
• 5-6: medium body. Pleasant, with presence but without heaviness. Most standard-filter coffees.
• 7-8: full body. Oily, round. French Press, Moka, some espressos.
• 9-10: heavy body. Syrupy, leaves a trail. Only methods with high oil retention or very particular coffees.

How it affects the recipe

More body in the profile steers the engine toward tighter ratios (more coffee per ml of water), longer times, and slightly finer grind. These parameters increase the extraction of heavy compounds and lipids that give texture.

Sweetness

Sweetness in coffee is a confusing term. It's not added sugar. It's the natural sweetness sensation that appears when extraction is balanced: caramel, ripe fruit, milk chocolate, honey, depending on the bean. Under-extracted coffee tastes sour and empty; over-extracted coffee tastes bitter and dry; the right balance "tastes sweet" even without added sugar.

What each range means

• 0-2: absent sweetness. Empty or dry coffee. Usually indicates severe under or over-extraction.
• 3-4: low sweetness. Present but in the background.
• 5-6: medium sweetness. Rounds off the coffee without dominating. The comfort zone for most.
• 7-8: high sweetness. Evokes ripe fruit, light caramel, honey. Well-brewed speciality coffees.
• 9-10: very high sweetness. Rare to achieve without added sugar. Requires exceptional beans and precise execution.

How it affects the recipe

Sweetness is the most complex dimension: the engine optimises it by seeking the point where total extraction (EY) lands in the SCA optimal zone, typically between 18 and 22 per cent. More sweetness means balancing temperature and grind to seek centred extractions, neither short nor long.

Bitterness

Bitterness is the sensation perceived at the back of the tongue and palate. In moderate doses it's part of coffee's character. In excess it masks everything else and produces astringency.

What each range means

• 0-2: almost absent bitterness. Very clean coffee, almost sweet in aftertaste. Rare and usually a sign of under-extraction.
• 3-4: low bitterness. Present as a frame, not a protagonist. Well-executed light filters.
• 5-6: medium bitterness. Balances sweetness. Most well-brewed coffees.
• 7-8: high bitterness. Marked, characteristic of traditional Italian espresso, Moka, dark roasts.
• 9-10: very high bitterness. Dominant. Only specific profiles from robusta beans or forced extractions.

How it affects the recipe

More bitterness in the profile usually leads to finer grind, longer times, and in some methods slightly higher temperature. These vectors favour the late extraction of bitter compounds (quinic acid, degraded trigonelline, certain polyphenols).

Finish (aftertaste)

The finish is what lingers in the mouth after swallowing. It can be short and clean, long and complex, dry and astringent, or oily and persistent.

What each range means

• 0-2: very short finish. Disappears immediately. Light coffee without persistence.
• 3-4: short finish. Brief but pleasant.
• 5-6: medium finish. Standard persistence, remembered for a few seconds.
• 7-8: long finish. Layers of flavour that evolve after the sip. Complex, well-extracted coffees.
• 9-10: very long finish. Minutes of persistence, with notes appearing one after another. Only exceptional coffees.

How it affects the recipe

The finish correlates with well-balanced central extractions, with emphasis on the end of the process. The engine typically adjusts the extraction curve seeking the heavy compounds (which give persistence) to come out without reaching astringency.

04The eight brewing methods

Each method has its own calibration in the KULM engine. The physical constants of the model (extraction rate, absorption ratio, scaling factor) are tuned to reproduce the experimental results of Angeloni et al. (2019). Detailed profile per method follows.

05The recipe KULM gives you

The final recipe KULM calculates has five main parameters. Below we explain what each means and the important warnings for each parameter.

Coffee dose (grams)

The amount of ground coffee you'll use. KULM calculates this value from the canonical volume of the method and the ratio the engine decides based on your sensory profile.

Water (millilitres)

Amount of water to use. Fixed value per method in v1.0.

Warnings about water

• Use mineralised but not hard water. Water with total TDS between 75 and 150 ppm is the SCA recommended range. Distilled water under-extracts; very hard water over-extracts and leaves metallic taste.
• If you live in a hard-water zone, consider filtering. A Brita jug or similar filter is usually enough.
• Volume includes bloom (pre-infusion) when applicable, but does not include filter rinse water.

Ratio (coffee : water)

The proportion between coffee dose and water. Shown as 1:X format (for example 1:15 means 1 gram of coffee for every 15 ml of water).

Warnings about ratio

• Tighter ratio (1:12, 1:13) = more concentrated coffee, more body, more extraction.
• More open ratio (1:17, 1:18) = more dilute coffee, more subtle, less body.
• Ratio is the variable KULM most actively adjusts based on your sensory profile. It's the engine's main lever.

Water temperature (degrees Celsius)

Ideal water temperature when starting the brew. Typical range is 88 to 96 degrees Celsius.

Warnings about temperature

• Water cools down during pouring. If you use a kettle and pour immediately, the temperature on the coffee bed may be 2 to 5 degrees lower than what the thermometer reads. This is especially relevant in slow-pour methods (V60, Chemex).
• If you use a gooseneck kettle, temperature stabilises better but also loses 1-2 degrees during pouring.
• Without a thermometer: boil water, remove from heat, wait 30-45 seconds. You'll be close to 92-94°C.
• Boiling water (100°C) is never right. It burns coffee and extracts bitter compounds uncontrollably.

Grind (SCA number)

Grind size expressed on the SCA (Specialty Coffee Association) scale, from 1 (very fine, espresso) to 10 (very coarse, cold brew).

Critical warnings about grind

• SCA values are general reference, not direct equivalence with all grinders. Each grinder has its own scale. A "6 SCA" may be "18 Baratza Encore", "25 Comandante", "5 Wilfa Uniform", etc.
• Calibrate your grinder the first time: brew with KULM's SCA value as a starting point and adjust one or two clicks toward fine or coarse based on the result.
• In Settings you can toggle grind display between SCA number and text description ("medium-fine", "coarse", etc.).
• Grind uniformity matters as much as size. A blade grinder will never produce consistent results, even if the number is right.

Total time (minutes:seconds or hours for Cold Brew)

Extraction time from start to end. Does not include preparation times (heating water, weighing, grinding).

Warnings about time

• In filter methods with bloom, time includes the bloom. If KULM says 3:00 minutes for V60, that means 30-45 seconds of bloom + the rest of the pour.
• In Aeropress, time includes immersion + plunger press.
• In French Press, time is until plunger down, not after.
• In Espresso, it's time from pump start to cutting the flow.
• In Cold Brew, shown in hours format. 12h 00min means exactly twelve hours.

How to scale recipes keeping the ratio

If you want to brew more (or less) than KULM suggests, the rule is simple: multiply both values (coffee and water) by the same factor.

Example: KULM gives you a Chemex recipe of 30g coffee / 500ml water (ratio 1:16.7). If you want to brew for 4 people in a large Chemex: multiply by 2 and you'll have 60g coffee / 1000ml water (same ratio 1:16.7). Other parameters (temperature, grind, time) stay approximately the same, though for very large volumes time may need manual adjustment of 10 to 20 per cent extra.

06Brewing Control Chart

The Brewing Control Chart is the Specialty Coffee Association's standard for classifying filter coffee, established in 1955 by chemist E.E. Lockhart and updated in successive versions. KULM uses a v3 implementation with nine zones.

The two chart metrics

TDS (Total Dissolved Solids)

Total dissolved solids, expressed as a percentage. Measures the concentration of extracted compounds from the coffee in the final drink. Measured with a refractometer. SCA ranges for filter coffee go from 1.15 to 1.55 per cent, with 1.35 being the optimal centre.

EY (Extraction Yield)

Extraction yield, expressed as a percentage. Measures what proportion of the original ground coffee has passed into the drink. SCA ranges go from 18 to 22 per cent, with 20 being the optimal centre.

The nine classification zones

The chart divides the TDS-EY plane into a 3x3 grid resulting from combining three TDS ranges (weak, normal, strong) with three EY ranges (under-extracted, optimal, over-extracted).

How to read the chart in KULM

Every recipe KULM generates comes with its automatic BCC classification. You see the zone in the result, and you can tap the area to unfold the chart explanation with your current recipe point overlaid (on roadmap for v1.0.x).

What to do if you're in a suboptimal zone

• Under-extracted zone: the coffee tastes sour, empty, without sweetness. Adjust toward longer extraction: hotter water, finer grind, tighter ratio, or longer time.
• Over-extracted zone: the coffee tastes bitter, astringent, dry. Adjust toward shorter extraction: less hot water, coarser grind, more open ratio, or shorter time.
• Weak zone: the coffee tastes watery, little present. Increase coffee dose (tighten the ratio) keeping EY constant.
• Strong zone: the coffee tastes very intense, dense. Increase water (open the ratio) keeping EY constant.

07The scientific engine

KULM doesn't invent recipes. The engine is built on published scientific literature and industry standards. Here we explain what's behind and, more importantly, what's NOT there (the model's real limitations).

Scientific base

Kinetic model (Maille, 2019)

The engine core is a kinetic extraction model based on M.J. Maille's (2019) doctoral thesis: "Measuring Coffee Extraction Kinetics at Early Time Scales". The model captures how soluble solids transfer from coffee to water as a function of time, temperature, and particle size, with special precision in the first 30 seconds of extraction (the critical phase that defines acidity and brightness).

Empirical anchors (Angeloni et al., 2019)

Specific parameters for each brewing method are calibrated against the experimental data published by Angeloni et al. (2019) in their comparative study of eight brewing methods. KULM reproduces the measured TDS and EY values from that study with an average error below 10 per cent across all methods.

SCA classification (Lockhart, 1955 → current v3)

Each recipe's classification follows the SCA Brewing Control Chart standard, whose origin lies in E.E. Lockhart's foundational 1955 work and which has been updated in several versions. KULM uses the current v3 with nine zones.

Sensory mapping

Translation of sensory profile to physical parameters is based on shift bands ("bandShift") validated against descriptors from the SCA Flavor Wheel and Coffee Taster's Flavor Wheel.

Continuous validation

KULM's engine is automatically validated before every release through two self-test suites:

• 6 Angeloni anchor tests: the engine reproduces published experimental TDS and EY values for V60, Chemex, Aeropress, French Press, Cold Brew, Espresso and Moka with error <10 per cent.
• 20 directional sensory coherence tests: when a sensory profile shifts in a specific direction (for example, more acidity and less body), the engine responds by adjusting physical parameters in the direction expected by the literature.

No release goes to production without all 26 tests passing 100 per cent.

Model limitations (what it doesn't validate)

It's important to be honest about the engine's real limitations:

• The model assumes ideal conditions: SCA-standard water (75-150 ppm TDS), fresh coffee (10-20 days post-roast), moderate room temperature, uniform grind. If any of these conditions fail severely, the real result may deviate from the predicted.
• Specific roast doesn't enter the model: there's no differentiation between light, medium, or dark roast beyond what you adjust in the sensory profile. Very dark roasts require lower temperature and coarser grind than what KULM suggests by default for a given profile.
• Origin and processing don't enter: a washed Ethiopian and a natural Ethiopian behave differently even if the sensory profile is similar. KULM gives a starting point; you adjust.
• Specific grinder doesn't enter: as we've seen, SCA values are reference. Your grinder may require adjustment of one or two clicks.
• Manual technique doesn't enter: KULM doesn't know if you pour well, if you bloom correctly, if you agitate the coffee bed. It assumes competent execution.

When to trust and when to adjust manually

Trust the recipe when: it's the first time you're brewing that coffee, or you want to start from an objective point without prior bias, or you're exploring a new method. KULM's recipe will be approximately correct and give you a stable baseline for comparison.

Adjust manually when: you know that specific coffee and know it behaves differently (for example, a natural that needs lower temperature), or your grinder has a known profile that deviates from SCA standard, or you've detected a consistent bias in your previous brews. In these cases, move one or two parameters slightly and observe.

08History and preferences

Local history

Every recipe KULM generates and that you decide to brew is automatically saved to your device's history. It includes all parameters (input sensory profile, output recipe, BCC classification, date, and method).

History is 100 per cent local. It doesn't sync to the cloud, isn't uploaded to any server, isn't shared with Verde Urbano Style S.L. or Apple. If you uninstall the app, history is lost (unless you back up your iPhone/iPad via iCloud Backup or Finder).

Clearing history

From Settings → Privacy → Clear history you can delete all saved recipes. The action is permanent and irreversible. The confirmation warns you before proceeding.

Preferences

Grind display

From Settings → Preferences you can toggle how grind is shown in recipes:

• SCA number (default): shows values like "6.5" on the 1-10 SCA scale.
• Text description: shows "medium-fine", "coarse", etc.

Language

KULM automatically detects the system language (iOS) and applies it. If your system is in Spanish, KULM shows in Spanish; if in English, in English. There's no manual selector in v1.0.

09KULM Pro

KULM Pro unlocks the seven premium methods: V60, Chemex, Aeropress, French Press, Cold Brew, Espresso and Moka. The Kalita method is included in the free version with all functionality.

Purchase model

KULM Pro is a one-time purchase of €14.99. It's not a subscription. It doesn't renew. You pay once and keep it forever tied to your Apple ID.

How the purchase is handled

The purchase is processed entirely through Apple App Store using the StoreKit system. Verde Urbano Style S.L. doesn't receive, store, or access your payment data. Apple handles charging, country-specific taxes, and refunds if applicable.

Restore purchases

If you change devices (new iPhone or iPad) or reinstall the app, you can recover your previous purchase without paying again. Go to Settings → KULM Pro → Restore purchases. Your Apple ID must be logged in on the device and must be the same one used for the original purchase.

Family Sharing

KULM Pro is enabled for Apple Family Sharing. If your Apple Family has up to 6 members, all can access KULM Pro with a single purchase. This activates automatically on the other family member's device, with no additional steps.

10Support and contact

Report a problem

From Settings → Support → Report a problem, your email app opens with a predefined message addressed to soporte@kulm.app. The message automatically includes useful technical information: app version, iOS version, device model. This allows us to diagnose quickly without you having to look up that information manually.

You can add your problem description to the message body before sending it. Don't delete the technical information.

Suggestions and feedback

For feedback on features, improvement ideas, or requests for new methods, also write to soporte@kulm.app. We read all feedback and prioritise based on frequency.

Legal and privacy matters

For specifically legal matters (privacy policy inquiries, exercising GDPR rights, contractual disputes), use the dedicated address legal@kulm.app. This separation ensures your legal inquiry isn't lost in the general support flow.

How to give useful feedback

If you want your report to be as useful as possible:

• Describe what you expected vs what happened. "I expected X, I saw Y" is far more diagnostic than "it doesn't work".
• Include steps to reproduce if the problem is a bug. "I open the app → select V60 → put acidity at 7 → it doesn't advance" is pure gold for debugging.
• Attach screenshots if the screen shows something odd. An image is worth more than three paragraphs.
• Be specific about your context: which coffee you're using, which grinder, which method. This helps us differentiate engine bugs from specific calibration situations.

AAppendix A — Glossary

Technical terms appearing in the manual, explained for users who aren't professional baristas.

Bloom (pre-infusion)

Initial phase of filter coffee where the coffee is wetted with a small amount of water (typically twice the coffee weight) before starting the main pour. Releases gases from freshly roasted coffee and prepares the bed for uniform extraction. Usually lasts 30-45 seconds.

BCC (Brewing Control Chart)

SCA standard for classifying filter coffee based on TDS and EY. Divided into 9 zones. Mandatory reference in any speciality barista course since 1955.

Channeling

Extraction failure where water finds a preferred path through the coffee bed instead of distributing uniformly. Produces over-extracted and under-extracted zones in the same cup. Typical of non-uniform grind or careless pouring.

EY (Extraction Yield)

Extraction yield. Percentage of ground coffee that ends up dissolved in the final drink. SCA recommends 18-22%.

Conical vs flat filter

Conical: V-shape (e.g. V60). Flat: flat base (e.g. Kalita). Conical filters tend to produce more complex coffees but more sensitive to technique. Flat ones are more stable.

Immersion vs filter vs pressure

The three main method families. Immersion (French Press, Cold Brew): coffee and water in continuous contact. Filter (V60, Chemex, Kalita): water passes through the coffee bed gradually. Pressure (Espresso, Moka): water forces its way at high pressure.

Uniform grind

Quality of a grind where all particles have a similar size. Key for predictable extractions. Burr grinders produce uniform grind; blade grinders don't.

ppm (parts per million)

Concentration unit. In water, refers to total dissolved solids. Ideal SCA water: 75-150 ppm.

Refractometer

Optical measurement instrument that calculates TDS of a drink based on the refractive index of light. Coffee-dedicated refractometers (VST, Atago) cost €400-800. Without one, KULM's TDS is estimated, not measured.

SCA (Specialty Coffee Association)

Global professional organisation that defines quality, cupping, brewing, and training standards in speciality coffee.

TDS (Total Dissolved Solids)

Total dissolved solids. Percentage of dissolved matter in the final drink. Indicates concentration. SCA recommends 1.15-1.55% for filter coffee.

Light / medium / dark roast

Degree of coffee development during roasting. Light: bright acids, more aromatic complexity. Medium: acidity-sweetness balance. Dark: characteristic bitterness, less acidity, more body.

BAppendix B — Important warnings

The five critical warnings every KULM user should keep in mind. They're scattered throughout the manual but we centralise them here by practical importance.

CAppendix C — Frequently asked questions

What does KULM actually do?

KULM is an inverse coffee calculator. You describe the sensory profile you want (acidity, body, sweetness, bitterness, and finish) and KULM calculates the precise recipe (temperature, ratio, time, and grind) to achieve it. It uses an engine based on scientific literature and the SCA standard.

What do TDS and EY values mean?

TDS (total dissolved solids) measures coffee strength. EY (extraction yield) measures the percentage of coffee that has dissolved. Both are the two core metrics of the SCA Brewing Control Chart. KULM calculates them and classifies your recipe into zones (optimal, under-extracted, over-extracted, strong, weak, etc.).

Why does my coffee change in grams but not water?

KULM v1.0 uses typical water volumes per method (V60=250ml, Chemex=500ml, etc.) and calculates coffee grams from the optimal ratio the engine decides based on your sensory profile. To duplicate a recipe, multiply both values keeping the ratio. Future versions will let you adjust cup size.

What's the difference with KULM Pro?

Free KULM includes the complete Kalita method, with full engine and SCA classification. KULM Pro adds seven more methods: V60, Chemex, Aeropress, French Press, Cold Brew, Espresso and Moka. One-time payment of €14.99, never a subscription.

Does KULM need an internet connection?

No. KULM works fully offline. All calculations are local. Connection is only needed for the initial Pro purchase, which Apple handles.

Can I trust the recipes KULM gives me?

KULM is calibrated against published experimental data (Angeloni et al. 2019, Maille 2019) and classifies recipes using the SCA Brewing Control Chart standard. Still, every coffee is different: use KULM as a rigorous starting point, adjust to your palate, and repeat what works.

Can I use KULM with instant coffee or pods?

No. KULM is designed for freshly ground bean coffee. Instant coffee doesn't have classic extraction (it's already dissolved) and pods have their own parameters that don't match the modelled methods.

What to do if the result doesn't match what I expected?

First, review the five warnings in Appendix B. Second, consider whether your coffee is in ideal conditions (freshness, quality, grinder). Third, slightly adjust one or two parameters and try again. If you still see consistent deviations after several attempts, write to soporte@kulm.app with your specific context.

Is my data uploaded to the cloud?

No. KULM is 100% local. Your history, preferences, and profile stay exclusively on the device storage. See our privacy policy for more details.

Can I export my recipe history?

Not in v1.0. This feature is planned for a future version. For now, if you need to keep an especially valuable recipe, take a screenshot.