Trace: Soap & Lye Calculator

Trace is a cold-process soap calculator with cited chemistry. Every quality bound, every additive limit, every fragrance cap names its source. Paid once at $6.99 — no subscription, no ads, no scanner.

The wedge

Most soap calculators surface "soap qualities" (hardness, cleansing, conditioning, lather) as opaque numbers. Trace shows the same numbers — but on every bound, tap to see exactly which named source backs it. Hardness 29–54: per Kevin Dunn, Scientific Soapmaking (Hampden-Sydney College, 2010). Citric acid 0.624× extra NaOH: per Lovin' Soap Studio. IFRA Cat 9 fragrance caps: per the IFRA Standards 51st Amendment (2025).

For the calculator

• 31 oils with SAP values for NaOH (bar soap) and KOH (liquid soap), cross-checked against AOCS official methods and USDA Agricultural Handbook 8
• Dual-lye blends for cream soap and shaving soap
• Three water expressions interconvert cleanly: water % of oils, lye concentration %, water:lye ratio
• Superfat / lye-discount slider
• Citric acid auto-offsets the NaOH calculation (0.624× per Lovin' Soap Studio)
• Sodium lactate, ROE, and salt brine math with cited ranges
• IFRA Category 9 (rinse-off toilet soap) fragrance caps for 20 common essential oils
• 6 soap qualities computed from weighted-average fatty-acid composition: hardness, cleansing, conditioning, bubbly lather, creamy lather, longevity
• Adjustable lye purity for NaOH (default 99%) and KOH (default 90%)

For the soapmaker

• Brand-aware oil-supplier presets: Bramble Berry, Soaper's Choice, Bulk Apothecary, Essential Depot, Wholesale Supplies Plus, plus Costco / Trader Joe's / Spectrum generics
• Save a batch and start a 4-week cure timer
• Log cure events: gel check, unmold, zap test, pH test, notes
• Per-batch recipe lock — what you saved is what you read back

For your library

Every cited source listed in one Sources screen: Kevin Dunn (Scientific Soapmaking), AOCS, USDA Handbook 8, Susan Miller Cavitch (The Soapmaker's Companion), Anne L. Watson (Smart Soapmaking), Modern Soapmaking (Kenna Cote), Lovin' Soap Studio (Amanda Gail Aaron), IFRA Standards, Handcrafted Soap & Cosmetic Guild.

The Moon Dog promise

• Paid once at $6.99. No subscription. No ads.
• No account. No login. No signup. No network.
• Works fully offline.
• No data collection.

Disclaimer

Sodium hydroxide (NaOH) and potassium hydroxide (KOH) are corrosive and can cause serious burns or eye damage. Always follow your supplier's Material Safety Data Sheet (MSDS) and the safety practices recommended by the Handcrafted Soap & Cosmetic Guild (HSCG). Trace cites named sources but does not generate recipes — independent verification against your supplier's specifications is your responsibility.

© 2026 Roman Kopaliani