Lye

high hazard

Also: sodium hydroxide, caustic soda

CleaningHygiene

Soap-making alkali and a drain clearer. It can blind in seconds. It heats violently in water, hotter if you add water to lye instead of lye to water. It belongs in the den only if you will actually make soap and will kit up every time.

Shelf life: Indefinite if dry and sealed. It drinks water from air and cakes.
Container: HDPE or glass with a poly liner. NEVER aluminum. NEVER a metal paint can that can fizz hydrogen.
Grade: 100% sodium hydroxide, no drain-opener additives, no aluminum chips in the formula

What it does

▸Traditional bar soap with fats you already have
▸Unclogging some organic drains (commercial drain openers are often lye plus extras)

Store

▸Own shelf, own bin, skull label, child-locked.
▸Away from acids, aluminum, and anything you like.

Hazards

▸Severe chemical burns. Splash goggles that seal.
▸Always add lye to water, never water to lye.
▸Aluminum + lye → hydrogen gas (flammable) and a ruined pot.
▸Vinegar or citric ‘to neutralize a skin burn’ is the wrong move — flood with water 15+ minutes, then medical care.

Never mix

White vinegar Citric acid Household bleach Calcium hypochlorite Hydrogen peroxide 3%Baking soda

Also keep away from: aluminum, tin, zinc, acids of any kind, water poured onto lye (always lye into water).

Gear

Sealed splash goggles · Face shield if you have it · Heavy butyl or nitrile · Long sleeves · Vinegar nearby for SURFACE spills, not skin

In the field

If you do not make soap, do not store lye. The risk is not worth a drain you can rod by hand.

Soap math is by weight, not volume. Use a current lye calculator and a scale.

Source

Essential Depot-style 100% NaOH or a soap supplier. Hardware drain opener is often a blend — read.