Candle and soap calculator

Container: a round jar (inside diameter and height), a square jar or tin, a measured capacity (fill it with water and measure or weigh — 1 g is 1 ml), or a pillar mould’s volume. Fill to about 90 % of brim-full for containers.

Wax: each wax has a typical fill factor (grams of wax per millilitre of container, which allows for wax being lighter than water and shrinking as it sets), a typical and a maximum fragrance load, the temperature to add fragrance, the pouring range and the cure time. Fragrance and dye are percentages of the wax weight — the usual way they are quoted.

Wick: wick series from different makers are sized differently, so the tool gives a band for the diameter (small up to about 50 mm / 2"; two wicks above about 100 mm / 4") and the burn-test procedure to settle it, not a part number.

Oils: pick from 36 oils, butters and fats and give each a weight, or percentages with a total oil weight, or percentages and a mould: length × width × soap height × 0.40 oz of oil per cubic inch (about 0.69 g per ml), the usual rule.

Lye: sodium hydroxide for bars or potassium hydroxide for liquid soap (KOH is usually about 90 % pure). Lye = Σ oil × its SAP value × (1 − superfat). The table keeps KOH saponification values; NaOH values are KOH × 40.00 / 56.11 — olive oil comes out at 0.1347 g of NaOH per gram.

Water: by lye concentration (25–40 %, 33 % to start), water : lye ratio, or the old % of oils.

Quality numbers come from the oils' fatty-acid profiles: hardness (lauric + myristic + palmitic
stearic), cleansing (lauric + myristic), conditioning (oleic + linoleic + linolenic + ricinoleic), bubbly (lauric + myristic + ricinoleic) and creamy (palmitic + stearic + ricinoleic), plus iodine and INS, against the usual suggested ranges. A 100 % olive oil soap reads 17 / 0 / 82 / 0 / 17, iodine 85, INS 105.

Warnings flag lye concentrations outside 25–40 %, too little or too much superfat, a lot of castor, high cleansing and soft, rancidity-prone recipes.