Published · ANFA Chemical technical team
Ammonium bifluoride (NH4HF2, CAS 1341-49-7) is one of the most widely used chemicals for decorative glass frosting and etching. Because it is supplied as a solid, it is easier to store, weigh and dose than hydrofluoric acid, while still delivering the fluoride chemistry needed to attack glass.
Why ammonium bifluoride etches glass
Common soda-lime glass is built on a silica (SiO2) network. In water, ammonium bifluoride forms an acidic fluoride solution that reacts with silica to give soluble or loosely bound fluorosilicate salts. A simplified overall reaction is:
SiO₂ + 3 NH₄HF₂ → (NH₄)₂SiF₆ + NH₃ + 2 H₂O
The ammonium fluorosilicate crystals that form on the surface scatter light, which is what produces the even, satin or matte "frosted" look. Deeper or clearer etching is obtained when the reaction products are removed more aggressively or when stronger fluoride systems are used.
Typical frosting and etching process
- Cleaning – remove oil, dust and residues so the etch is uniform.
- Masking (for patterns) – protect areas that must stay clear with acid-resistant film or resist.
- Application – dip, spray or apply a frosting solution or paste based on ammonium bifluoride. Formulations often contain additional salts, acids or thickeners; the exact recipe, concentration, temperature and contact time are set by each glass processor.
- Rinsing – rinse thoroughly with water to stop the reaction and remove fluorosilicate residues.
- Neutralisation and wastewater treatment – fluoride-bearing effluent must be treated (commonly by precipitation with lime) according to local regulations.
Choosing the right grade
For glass work, consistent assay and low impurities matter because they affect surface uniformity. ANFA's ammonium bifluoride is produced to HG/T 3586; the export grade is held at ≥ 98.0% NH4HF2 (dry basis) with loss on drying ≤ 1.5%. It is packed in 25 kg woven bags with PE liner or 1000 kg jumbo bags.
Ammonium bifluoride is deliquescent and tends to cake, so keep bags closed and store them in a cool, dry place away from glass and bare metal containers.
Safety essentials
- Ammonium bifluoride is a Class 8 corrosive (UN 1727). In contact with acids or heat it releases hydrogen fluoride.
- Wear chemical goggles, face shield, acid-resistant gloves and protective clothing; work with good ventilation.
- Fluoride burns can be painless at first. Keep calcium gluconate gel available and seek medical help after any skin contact.
Related products
Glass processors also use sodium bifluoride in etching powders, and our custom fluoride blends team can help adapt formulations. SDS and COA are provided upon inquiry confirmation.