NibFlow

Stop guessing which fountain pen to use today. NibFlow checks your local humidity and temperature, then scores every pen + ink + paper combo in your collection — so you know which one flows best right now. Fountain pen users know the frustration: an ink that wrote flawlessly yesterday feathers or dries out today. The reason? Weather changed. Humidity, temperature, and dew point all affect how ink flows through your nib. HOW IT WORKS 1. Add your pen + ink combo: select nib size, ink type, wetness, and paper grade. 2. NibFlow fetches your local weather and calculates a Flow Score (0–100) across four axes: dry risk, feathering, dry time, and bleed-through. 3. See your daily score, care tips, and which combo to use today. It takes 15 seconds to set up. No account required. YOUR DAILY FLOW SCORE Each combo gets a score from 0 to 100 based on four factors: how likely your nib dries out, how much your ink feathers on paper, how long it takes to dry, and whether it bleeds through. The score updates every time weather changes. CARE TIPS Get daily suggestions tailored to your combo: "Cap your EF between paragraphs today" or "Switch to heavier paper — bleed risk is high." Upgrade to Pro for deeper insights: - Unlimited pen + ink combos with daily ranking - Full 4-axis breakdown with cause explanations - 7-day flow forecast - Brand-level paper grades (Tomoe River, Rhodia, Clairefontaine, and more) - Morning flow alert notifications - Collection statistics PRIVACY FIRST All your pen and ink data is stored locally on your device. No account needed. No tracking. Location is used only to fetch weather data from Open-Meteo. Your coordinates are never stored on any server. This app provides flow estimates based on general relationships between weather conditions and ink behavior. It is not a substitute for hands-on writing experience. Actual performance varies by specific ink formulation, nib condition, and paper brand. Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/