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What it is. This custom mix is hydrofluoric acid diluted 1:20 in deionized water, supplied in a 100 mL size. It is a controlled-strength HF etchant for gentle glass etching, native oxide removal, and analytical sample preparation.
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How strong a 1:20 dilution is. Assuming one volume of 49% HF mixed with twenty volumes of deionized water, the solution contains roughly 2 to 3% HF (calculated). Confirm the ratio based on the label, since 1:20 can also describe one part in twenty total.
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Why a dilute HF mix. Dilute HF etches silicon dioxide slowly and evenly, which suits removing thin native oxide from silicon, light glass frosting, and cleaning steps where concentrated acid would act too fast. The small 100 mL size suits labs that need occasional, measured use.
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Deionized water matters. Mixing with deionized water keeps the etchant free of calcium, magnesium, and other ions that would react with fluoride or leave residues on clean surfaces. That is important in semiconductor and trace-analysis work.
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Checking the etch. Hydrophobic behavior is a common quick check for oxide removal from silicon: once the oxide is gone, water beads up and runs off the clean surface. Rinse parts thoroughly in deionized water after etching to stop the reaction.
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Custom mixes save handling. Preparing dilute HF in-house means opening and measuring concentrated acid, which carries the greatest exposure risk. A ready-made 1:20 mix removes that step. For other strengths, see Lab Pro's Hydrofluoric Acid 10% Solution and Hydrofluoric Acid 49%, ACS Grade.
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Compatible labware. Use only polyethylene, polypropylene, or fluoropolymer labware. HF etches glass and quartz even at low concentrations.
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Dilute does not mean safe. Fluoride from dilute HF still penetrates skin, and burns may not hurt for hours. Wear HF-rated gloves, goggles, and a face shield; work in a fume hood; and keep calcium gluconate gel within reach. Lab Pro offers Calgonate 2.5% Calcium Gluconate Gel.
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Where it is used. Dilute 1:20 HF is used to remove native oxide before deposition or contact formation, gently etch glass, clean silicon and glass surfaces, prepare samples for trace-element analysis, and teach labs demonstrating oxide etching under supervision.
Technical Specifications
| Chemical Name |
Hydrofluoric acid, aqueous solution |
| CAS Numbers |
7664-39-3 (hydrogen fluoride); 7732-18-5 (water) |
| EC Number (HF) |
231-634-8 |
| Synonyms |
Hydrogen fluoride solution, fluoric acid, HF |
| Formula (active) |
HF |
| Molecular Weight (active) |
20.01 g/mol |
| Dilution |
1:20 hydrofluoric acid in deionized water |
| Approximate HF Content |
About 2 to 3% (calculated, assuming 1 vol 49% HF + 20 vol water) |
| Diluent |
Deionized water |
| Appearance |
Clear, colorless liquid |
| Compatible Labware |
Polyethylene, polypropylene, fluoropolymer |
| Hazard Profile |
Toxic and corrosive at any concentration; confirm GHS classification on SDS |
| DOT |
UN1790, Hydrofluoric acid; confirm class and packing group on SDS |
| First Aid Requirement |
Calcium gluconate gel on hand |
| Product Type |
Custom mix |
| Package Size |
100 mL |
Applications / Common Uses
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Native oxide removal: Strips thin oxide from silicon before processing.
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Gentle glass etching: Frosts or cleans glass at a controlled rate.
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Surface cleaning: Cleans silicon and glass surfaces.
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Trace-analysis prep: Supports dissolution of silica-containing samples.
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Supervised teaching: Demonstrates oxide etching at low strength.
Storage, Handling & Shipping
Caution: Hydrofluoric acid is acutely toxic and corrosive. Skin contact may cause delayed, deep tissue injury and potentially fatal systemic fluoride poisoning, sometimes without immediate pain. Handle only in a fume hood with HF-rated gloves, a face shield, goggles, and an apron, and keep calcium gluconate gel within reach.
Store tightly closed in polyethylene, polypropylene, or fluoropolymer containers in a cool, ventilated, locked corrosives area, away from glass, ceramics, metals, bases, and oxidizers. Restrict access to trained users, and keep calcium gluconate gel and an HF-specific spill kit nearby.
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Incompatible materials: Glass, ceramics, concrete, metals, bases, and oxidizers.
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Exposure limits (hydrogen fluoride): OSHA PEL 3 ppm TWA; NIOSH REL 3 ppm TWA, 6 ppm ceiling (15 min).
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Spill response: Evacuate, ventilate, and use an HF-specific spill kit or calcium-based absorbent. Do not use silica-based absorbents.
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First aid: Skin: rinse with water, apply calcium gluconate gel, and seek emergency care. Eyes: flush for 15 minutes and seek immediate care.
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