Dip your indicator. Point your camera. Read the number. That's the whole lab.
How it works
Add a drop of pH indicator to your sample.
Frame it in the circle with the gray card beside it. The card lets the app cancel out your lighting.
Press Read pH — the color becomes a number, with an honest ± on it.
Prepare a solution of known pH (verified with a pH meter or a fresh buffer), add your indicator, frame it like a normal measurement, enter its pH and capture. Aim for at least 8 points spread across the range you care about. Several captures at the same pH under different lighting make the model tougher.
| color | pH | Lab distance ref |
|---|
A code contains the whole calibration — paste it anywhere: chat, email, a QR code. Anyone who enters it (or opens the share link) gets your exact calibration.
Learning mode
Five questions per round, generated from a pH — scanned or random.
Întrebările din quiz sunt deocamdată în engleză — traducerea lor e pe drum.
Why a color can be a number.
The chemistry behind pH Whisperer — from protons to pixels.
What pH actually is
pH measures how acidic or basic a solution is by counting its hydrogen
ions: pH = −log₁₀[H⁺]. The logarithm is the part people forget —
each step of one pH unit means ten times more or fewer hydrogen
ions. Lemon juice (~pH 2) isn't a bit more acidic than milk (~pH 6.7); it's
tens of thousands of times more acidic. Water sits near 7, and the WHO
guideline for drinking water is 6.5–8.5.
Why indicators change color
Light interacts with a substance at the level of its electron orbitals. A pH indicator is a molecule whose structure — and therefore its electron distribution — changes when it gains or loses protons, and protonation is directly tied to the pH of the solution around it.
Each of these forms has its own distinct absorbance curve in the visible spectrum: it swallows some wavelengths and lets others pass. The color you see is the light that survives. Change the pH → change the molecule's form → change which wavelengths are absorbed → a different color reaches your eye.
Absorbance is itself a logarithmic scale: one extra unit of absorbance means ten times less light transmitted. pH is a logarithm read through another logarithm — and yet your eye does it effortlessly.
From color to number
If each pH produces a characteristic color, then a photograph of the color carries information about the pH — a camera can do what your eye does, but objectively. The program behind pH Whisperer assigns a pH score to the color it sees, based on a database of reference photos it was trained on.
These programs are sensitive to small changes in conditions, which is why every photo includes a gray card as a color reference and why lighting is kept constant.
One drop, many jobs.
Anywhere a color can speak, pH Whisperer can listen.
Water monitoring
Check wells, tanks, rivers or tap water against the WHO guideline band (6.5–8.5), marked right on the scale. A quick first look that tells you when water deserves a proper lab test.
Soil pH for gardens
Mix a spoonful of soil with twice as much distilled water, shake, let it settle, and read the clear layer above. Soil pH decides which nutrients plants can actually absorb.
School laboratories
One teacher calibrates, prints the QR code, and every student's phone becomes an instrument — the whole class measures at the same time.
Learning at home
Boil red cabbage for a homemade indicator and test the kitchen — lemon, soap, vinegar, milk. Everyday liquids are safe; stronger ones belong in adult hands.
And beyond
Aquariums and hydroponics live by pH — and any test strip that answers in color (nitrate, chlorine, hardness) could be read the same way.
Why we made this.
pH Whisperer began as a project for a chemistry × AI conference, where we — Amina and Luca — presented our invention: a program that reads the pH of a solution from the color of its indicator. We're 11th-grade students at Tudor Vianu National Computer Science College.
After the conference, a simple fact kept bothering us: a good pH meter costs from tens to hundreds of euros, needs calibration buffers, storage solution, and careful maintenance, while a phone with a camera is already in almost everyone's pocket. So we rebuilt the idea as a free web app: for schools that can't buy a meter for every bench, for anyone checking their water or soil, for kids discovering chemistry at home.
Every reading comes with a ± value, and the app tells you when a color is unlike anything it has been calibrated on instead of inventing a confident number.