The names sound alike but these are different chemicals for different jobs. Here is how to choose.
| Borax | Borax substitute | |
|---|---|---|
| Chemical | Sodium tetraborate decahydrate | Sodium sesquicarbonate (carbonate + bicarbonate) |
| Contains boron | Yes | No |
| pH in water | about 9.2 | about 9.8–10 |
| UK availability | Professional/trade use only | Anyone |
| Best for | Flux, glazes, timber, lab buffers | Laundry, stains, cleaning, water softening |
| Hazard | Repr. 1B (H360FD) | Eye irritant |
When You Need Real Borax
Choose pure borax powder when the boron chemistry matters: flux for soldering, glaze recipes, borate timber treatments and laboratory buffers. A carbonate blend will not do these jobs.
When Borax Substitute Is Better
For washing, stain soaking, softening hard water and household cleaning, borax substitute does the job well and is legal for home use.
Can I Make Slime with Borax Substitute?
No. Slime relies on borate ions cross-linking PVA glue, and borax substitute contains no boron. Pure borax must not be sold for slime making.