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Compounds and Cleaning · Compound · Magnesium sulfate

Epsom Salt

Magnesium sulfate. It is the traditional addition to a warm muscle soak, feeds magnesium to plants where a soil test shows a shortfall, and works as a saline laxative.

INDEFINITEMULTI-USEWorks without power

Quick facts

Is
Magnesium sulfate
Form
White crystals
Hazard class
Low
Shelf life
Indefinite
Storage
Airtight container
What to avoid
Damp and very dry air

See everything epsom salt must never touch

What it's good for

Warm soaks

The classic muscle soak

Plants

Magnesium, if soil-tested

Digestion

Saline laxative

Soak & scrub

Foot soaks

Magnesium sulfate that dissolves easily: the traditional addition to a warm soak, a magnesium feed for deficient soil, and a saline laxative.

Good to know

The name is a chemistry accident. Epsom salt shares nothing with table salt but the look: it is magnesium sulfate, drawn originally from a bitter spring at Epsom in England. Swallowed, it pulls water into the gut and empties it fast, which is why the label sets hard limits. In soil it supplies magnesium, the ion sitting at the center of every chlorophyll molecule, so a short plant yellows between the veins of its older, lower leaves first, stripping the old growth to feed the new.

Handling and safety

The classic muscle soak

The traditional addition to a warm soak; the warmth does most of the work.

Magnesium for plants

Corrects a magnesium deficiency, but only where a soil test confirms one.

Saline laxative

It acts fast and hard by osmosis. Follow the package and do not overuse.

Dissolves easily

It mixes quickly into warm water for soaks and sprays.

Eight jobs it does

  • Soak sore muscles and feet
  • Draw out splinters and infection
  • Magnesium fertilizer for plants
  • Lawn and garden greener
  • Constipation relief (per label)
  • Seed sprouting booster
  • Bath salt for joint pain
  • Reduce swelling on bites

If it goes bad Clumps with moisture. Break it up and it still dissolves and works.

Recipes for epsom salt

Questions this answers

Tap a question for the short answer.

What is epsom salt used for?

Epsom salt is magnesium sulfate. It is the traditional addition to a warm soak for sore muscles and feet, a magnesium feed for plants where a soil test confirms a shortfall, and a saline laxative used per the package label. Other jobs include drawing out splinters and reducing swelling on bites.

How long does epsom salt last in storage?

Epsom salt has an indefinite shelf life. If it picks up moisture it clumps, but you can break it up and it still dissolves and works.

How do I store epsom salt?

Keep it in an airtight container, away from damp and very dry air. If moisture gets in it will clump, but once broken up it still dissolves and works fine.

Keep going

Read nextPotassium NitrateSaltpeter. It cures meat, rots out tree stumps, feeds plants, and acts as a versatile oxidizer.Compounds and Cleaning · Compound

Related to this

Garden and Livestock · Formula Garden Fertilizer for Magnesium-Deficient Plants When OLDER leaves yellow between the veins while the veins stay green, and a soil test confirms low magnesium, Epsom salt fixes what nitrogen and potassium cannot. On soils that already have enough magnesium, though, it does nothing and can even do harm. Handle with care Hygiene and Sanitation · Formula Muscle Soak for Soreness and Recovery A warm soak eases sore, tense muscles after hard work. The warmth is doing the work: there is no good evidence the Epsom salt adds anything beyond the warm water. It is comforting, cheap, and low-risk as long as the water stays warm rather than hot. Handle with care Medical · Formula Emergency Laxative for Constipation Relief Taken by mouth, Epsom salt pulls water into the bowel and empties it, usually within half an hour to six hours. It is a real medicine with a real dose, not a home remedy: follow the label, and know when to stop. Handle with care Compounds and Cleaning · Compound Citric Acid Shelf life: Indefinite. Storage: Airtight glass or plastic. INDEFINITEHandle with care
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Compounds and Cleaning · CompoundSource: Prepper's Chemical Survival Guide, Chapter 34, p. 173 · Last reviewed 2026-09-18

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