Bleach is a solution of sodium hypochlorite dissolved in water, and it’s produced commercially through a well-established chemical process that combines chlorine with a sodium hydroxide solution. Standard household bleach contains 5.25% to 6.15% sodium hypochlorite. While industrial manufacturing requires specialized equipment, you can prepare bleach solutions at safe working concentrations from commercially available powdered bleach for cleaning and disinfection purposes.
How Bleach Is Made Industrially
Nearly all liquid bleach on store shelves comes from a process called the chloralkali method. A factory passes an electrical current (typically 2 to 4 volts of direct current) through a tank of saltwater, which is essentially a 3% solution of sodium chloride. The electricity splits the salt and water into new components: chlorine gas forms at the positive electrode, while hydrogen gas and sodium hydroxide form at the negative electrode.
Those products then react inside the same tank. The chlorine gas dissolves into the sodium hydroxide solution, producing sodium hypochlorite, which is the active ingredient in bleach. A small amount of ordinary table salt re-forms as a byproduct. The manufacturer then adjusts the concentration, adds stabilizers, and bottles the result. This is a continuous, tightly controlled process that produces chlorine gas as an intermediate step, which is why it belongs in a factory rather than a kitchen.
Making a Bleach Solution From Powder
The practical way to make bleach at home is to dissolve calcium hypochlorite powder (sometimes sold as “bleach powder” or pool shock) into water. This is especially useful in emergencies or areas where liquid bleach isn’t available. The CDC provides a straightforward formula for getting the concentration right:
Grams of powder per liter of water = (desired chlorine percentage ÷ chlorine percentage listed on the powder) × 1,000
For example, if your bleach powder contains 35% active chlorine and you want a 0.5% chlorine solution (suitable for surface disinfection), the math works out to 14.3 grams of powder per liter of water. A standard kitchen scale and a clean container are all you need. Stir until the powder fully dissolves, and the solution is ready to use.
If you want a stronger solution closer to store-bought bleach (around 5% to 6%), you would need significantly more powder per liter. Keep in mind that higher concentrations are more irritating to skin and airways, so protective gloves are important.
How Long Bleach Stays Effective
Bleach degrades over time regardless of how it’s made. Research on sodium hypochlorite solutions stored in amber glass bottles at room temperature found that roughly 5.24% of the available chlorine is lost per year. At that rate, the solution stays above 90% of its original strength for about 23 months. That’s nearly two years of reliable potency when stored properly.
Heat and sunlight speed up degradation considerably. Store your bleach, whether homemade or commercial, in an opaque container in a cool, dark place. Solutions you mix from powder tend to degrade faster than factory-stabilized products, so it’s best to prepare only what you’ll use within a few weeks.
Testing the Concentration
If you’re mixing bleach from powder for water treatment or serious disinfection, you may want to verify the strength. The standard method is an iodometric titration: you add potassium iodide and an acid reagent to a water sample containing a small amount of your bleach, then slowly add a thiosulfate solution until the color disappears. The amount of thiosulfate used tells you the chlorine concentration.
For most household cleaning, this level of precision isn’t necessary. Pool supply stores sell inexpensive chlorine test strips that give a quick reading. If you’re using bleach for drinking water purification in an emergency, though, confirming the concentration matters because too little won’t disinfect and too much is unsafe to drink.
Dangerous Combinations to Avoid
Bleach reacts violently with several common household chemicals, and the gases produced can be life-threatening in enclosed spaces.
- Bleach and vinegar produce chlorine gas, which causes coughing, burning eyes, and serious breathing difficulty.
- Bleach and ammonia produce chloramine gas, which causes shortness of breath and chest pain.
- Bleach and rubbing alcohol produce chloroform, which is highly toxic even in small amounts.
Many glass cleaners contain ammonia and many bathroom cleaners contain acids, so never mix bleach with any other cleaning product. If you accidentally create a mix, leave the area immediately and get to fresh air.
Handling Bleach Safely
Even standard household bleach at 5% to 6% concentration is a strong oxidizer that can burn skin and damage eyes on contact. When working with bleach powder or concentrated solutions, wear nitrile, neoprene, or butyl rubber gloves. Regular latex gloves also work for brief contact with diluted solutions. Work in a well-ventilated area, and avoid breathing directly over an open container.
Concentrated bleach solutions or powder can release enough chlorine vapor to irritate your lungs. If you’re dissolving large amounts of powder, do it outdoors or near an open window. Keep bleach away from metals (it corrodes most of them), colored fabrics, and wood surfaces. Rinse any skin contact with plenty of water right away.