Borax powder (sodium tetraborate decahydrate) is one of the most versatile industrial minerals. It melts into a glassy flux, dissolves into a stable alkaline buffer and inhibits fungal growth. These are its main professional uses.
1. Flux for soldering, brazing and casting
When heated, borax loses its water of crystallisation and melts into a clear glass that dissolves metal oxides and shields hot metal from air. Jewellers use it when soldering gold and silver, blacksmiths use it for forge welding, and casters add it to crucibles. See our dedicated guide to borax flux.
2. Ceramic glazes, enamels and glass
Boron is a powerful glass former and flux. Potters use borax and other boron sources to lower glaze melting temperatures, reduce crazing and brighten colours. It is also a key ingredient in borosilicate glass and vitreous enamels. Because borax is water soluble it is often used in fritted form for glaze batches, but raw borax remains common in studio testing and low-fire work. Read more in our guide to borax for pottery and ceramic glazes.
3. Timber treatment and building restoration
Borate solutions penetrate timber and protect it against wood-boring insects and fungal decay such as dry rot. Restoration specialists use borax, often combined with boric acid, to treat historic timbers, joists and roof structures. Treatment should always follow the product SDS and relevant building conservation guidance.
4. Laboratory buffer solutions
Sodium tetraborate is a standard reagent for borate buffers in the pH 8–10 range, used in electrophoresis and enzyme assays, and as a pH reference standard (pH 9.18 at 25 °C for a 0.01 mol/kg solution). For solubility figures and a step-by-step method, see our guide on how to dissolve borax powder.
Borax is also the classic flux for the borax bead test, a traditional qualitative test for metals such as copper, cobalt and iron. Our guide to the borax bead test explains the method and the bead colours.
5. Taxidermy and botanical preservation
Borax has long been used as a drying and preserving agent for skins and specimens, and in mixtures for drying flowers.
6. Industrial cleaning and water conditioning
In workshops and professional kitchens, borax solutions help remove grease, carbon and mineral deposits. It also softens water by binding calcium and magnesium, and is used to condition water in closed technical systems.
7. Manufacturing
Industry uses borates in detergents, adhesives, fire retardants, fibreglass insulation, metallurgy and agriculture, where boron is an essential plant micronutrient.
Handling borax safely
- Wear nitrile gloves and safety glasses, and avoid raising dust.
- Work in a ventilated area and wash hands after use.
- Keep in the original labelled container, away from food and children.
- Borax is classified Repr. 1B (H360FD) and is supplied for professional use only. It must not be used in food, cosmetics or toys such as slime.
For PPE, storage, spills, exposure limits and first aid, see our full borax safety guide.
For household laundry and cleaning, use borax substitute instead. Wondering about the rules? Read Is borax banned in the UK?
Need borax for professional use? Our 99.9% pure borax powder is available in 900g and 3kg packs with SDS and free delivery to the UK. For home laundry and cleaning, choose our borax substitute.