Boric Acid: Uses, Grades and Safety

Boric acid is a weak acid of boron that comes as white powder or colourless, slightly pearly flakes. Most Indian buyers ask for it as boric powder (बोरिक पाउडर). It's mild compared with mineral acids like hydrochloric acid, but it's still a chemical and not for eating.

• Formula: H3BO3
• CAS number: 10043-35-3
• Molar mass: about 61.83 g/mol
• Melting point: about 171 °C. On further heating it loses water and turns into a glassy boron oxide.
• Solubility in water: about 2.5 g per 100 mL at 0 °C, 4.7 g at 20 °C, and 27.5 g at 100 °C

That big jump in solubility with temperature is worth remembering. Hot water dissolves far more, and the excess crystallises back out as the solution cools.

Azlok's boric acid listings are technical grade powder in three sizes, 100 g, 200 g and 600 g. None is sold as IP, lab or food grade.

To compare the three packs, see today's price per kg.

• Household and games: carrom board powder. A light dusting makes the striker and coins glide.
• Glass and fibreglass: a source of boron for borosilicate glass, glass wool and textile fibreglass.
• Ceramics and enamels: lowers melting temperature and improves gloss in glazes and vitreous enamel.
• Metalwork: mixed with borax as a brazing and forge-welding flux.
• Fire retardants: used with borax to treat wood, paper, cellulose insulation and cotton.
• Lab and electroplating: borate buffers and nickel plating baths, which need a suitable lab or plating grade.

Carrom board: sprinkle a small pinch, about half a teaspoon, across the playing surface. Spread it lightly with your palm or a dry cloth, then flick off the excess. Too much makes the coins skid wildly and leaves white patches. Wipe the board with a dry cloth after play, and wash your hands.

Making a solution: plan on about 4.5 to 5 g per 100 mL of water at room temperature. If you need it stronger, use hot water, but expect crystals to come back as it cools. Stir until fully clear before use.

Brazing or forge flux: mix boric acid with borax, roughly equal parts as a starting point, and make a paste with a little water or alcohol. Apply it to clean metal before heating. Fluxes vary by metal, so follow your brazing rod maker's advice where available.

Glazes: use it only as part of a tested recipe. Boric acid is water-soluble, so it can migrate as a wet glaze dries. Many potters prefer frits for this reason.

• Boric acid isn't for eating or drinking. Don't use it in food, rice or flour storage, or homemade remedies.
• It's classified in the EU as toxic for reproduction. It may damage fertility and the unborn child. Pregnant women should avoid handling it.
• Keep it away from children and pets. Small children have been poisoned by boric powder mistaken for sugar or salt.
• Wear gloves and avoid breathing the dust. Wash your hands after use, especially after carrom.
• If it gets in your eyes, rinse with clean water for several minutes.
• Keep it away from strong bases and reactive metals such as potassium.
• Store it in its original, clearly labelled container, tightly closed, in a dry place away from the kitchen.
• Don't pour large amounts into soil, ponds or garden beds. Excess boron harms plants.

For a carrom board at home, the 100 g pack lasts many months. Clubs and shops that refill boards daily do better with 200 g or 600 g. Workshops doing regular brazing or glaze work will find 600 g more practical.

Technical grade suits all the uses on this page. It's not suitable for pharma, cosmetic, food or analytical use. Glass, ceramics and plating units needing 25 kg or more can contact us through our bulk inquiry page with the grade, form (powder or granules) and monthly quantity.