• Batter: oils and lye solution mixed together, before the soap sets.

• Castile: soap made from 100% olive oil. People also loosely use it for any mostly-olive soap ("bastile").

• Cold process (CP): mixing oils and lye solution at moderate temperatures, pouring into a mold, and curing for weeks.

• Cure: the weeks after unmolding when water evaporates and the bar gets harder and milder.

• DOS (dreaded orange spots): orange spots from rancid oils.

• Essential oil (EO): a concentrated oil distilled or pressed from plants, used for scent.

• Fragrance oil (FO): a blended scent made for products like soap.

• Gel phase: a warm stage after pouring when soap turns darker and translucent before setting. It's optional.

• Glycerin: a natural byproduct of saponification that stays in handmade soap.

• Hot process (HP): cooking the soap batter until saponification is complete before molding.

• IFRA: International Fragrance Association. Its standards set maximum use levels for fragrance materials in each product type. Soap is Category 9.

• INS: a SoapCalc number that combines iodine and SAP values to roughly predict bar hardness. 136–165 is SoapCalc's suggested range.

• Iodine value: how unsaturated (soft and liquid) an oil is. Lower means a harder bar.

• KOH (potassium hydroxide): the lye used for liquid and soft soap.

• Lye: the alkali that turns oils into soap. Usually NaOH or KOH.

• Lye-heavy: soap with leftover unreacted lye. Don't use it on skin.

• Lye concentration: lye ÷ (lye + water), as a percentage.

• Melt and pour (M&P): ready-made soap base that you melt, customize and pour. No lye handling.

• Mica: shimmery mineral-based colorant powder.

• NaOH (sodium hydroxide): the lye used for bar soap. Also called caustic soda.

• PPO: per pound of oils.

• Rebatch: grating and remelting soap to fix or add to it.

• Ricing: small rice-like lumps in batter, usually caused by a fragrance oil.

• SAP value (saponification value): how much lye one gram of a specific oil needs to become soap.

• Saponification: the chemical reaction between oils and lye that makes soap and glycerin.

• Seizing: batter that suddenly turns solid and can't be poured.

• Soda ash: a harmless white powder that sometimes forms on top of new soap.

• Superfat: the percentage of oils left unsaponified on purpose, for a cushion and a gentler bar.

• Trace: the point where batter has thickened enough that drips leave a trail on the surface (light, medium or thick).

• True soap: soap made from fats or oils plus lye, cleaning only by those soap compounds, and sold only as soap (FDA definition).

• Water discount: using less water than a calculator's default.

• Water : lye ratio: the parts of water for each part of lye. 2:1 equals a 33.3% lye concentration.

Sources - SoapCalc: Getting Started and calculator help (SAP, iodine, INS and quality ranges). https://soapcalc.net/gettingstarted - FDA: Frequently Asked Questions on Soap (true soap definition). https://www.fda.gov/cosmetics/cosmetic-products/frequently-asked-questions-soap - IFRA Standards Library. https://ifrafragrance.org/standards-library - Soap Queen: Soapy Mess-Up Quick Guide (ricing, seizing, soda ash, DOS, rebatch). https://soapqueen.com/bath-and-body-tutorials/tips-and-tricks/soapy-mess-quick-guide/ - Bramble Berry: Beginner's Guide to Common Soap Making Oils (castile, "bastile"). https://www.brambleberry.com/beginner/beginners-guide-to-common-soapmaking-oils.html