How to Test Gold with Nitric Acid: Step-by-Step Safety & Accuracy Guide (2026)

By Hanna Silkwood, Quality Lead at True Assay | Last updated: May 14, 2026

Nitric acid is the gold standard for at-home gold testing — pun intended. Whether you call it a nitric acid gold test, an acid scratch test, or simply a gold acid test, this method has been the go-to for pawn shops, jewelers, and precious-metal resellers for decades. When used correctly, it can verify karat purity from 10K to 24K in under 30 seconds. When used incorrectly, it can ruin a piece of jewelry, damage your work surface, or worse, hurt you.

This guide walks you through exactly how to test gold with nitric acid the right way: the safety setup professionals use, the step-by-step testing procedure, how to read your results accurately, and the most common mistakes that cause false positives and negatives.

What You'll Need Before You Start

  • A gold testing kit with nitric acid solutions for 10K, 14K, 18K, and 22K (a complete True Assay kit includes all four)
  • A testing stone (black basalt scratch stone)
  • Nitrile gloves and safety glasses
  • A well-ventilated area — outdoors or near an open window
  • Baking soda and water nearby for neutralizing spills
  • Paper towels for cleanup

Safety First: Working With Nitric Acid

⚠️ SAFETY WARNING: Nitric acid is a strong oxidizer. It will burn skin, etch metal surfaces, and release irritating fumes. Always follow proper OSHA chemical handling guidelines when working with acid solutions.

Follow these rules every single time:

  1. Always wear gloves and eye protection. No exceptions.
  2. Work in ventilation. Never test indoors in a closed room.
  3. Keep baking soda on hand. A 1:1 baking soda and water paste neutralizes acid spills instantly.
  4. Store acids upright in a cool, dark place away from children and pets.
  5. Never mix acid bottles. Use one dropper per solution.

Step-by-Step: How to Test Gold with Nitric Acid

Step 1: Prepare Your Workspace

Lay down paper towels and set your testing stone on a flat, stable surface. Put on your gloves and glasses. Open your acid bottles and place them upright within easy reach.

Step 2: Rub the Jewelry on the Stone

Find an inconspicuous spot on the piece (inside a ring band, the back of a pendant). Rub the item firmly across the stone three or four times to leave a visible streak of gold roughly 1 inch long.

Step 3: Apply the Acid

Start with the acid that matches the karat stamp on the piece. If there's no stamp, start with 14K (the most common). Place a single drop of acid directly on the streak.

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Every True Assay Gold Testing Kit includes 10K, 14K, 18K & 22K nitric acid solutions, a basalt testing stone, and a quick-reference card.
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Step 4: Read the Reaction (10–20 Seconds)

  • Streak stays bright gold: The piece is at or above the tested karat.
  • Streak fades slowly: The piece is slightly below the tested karat.
  • Streak disappears quickly or turns green/brown: The piece is below the tested karat or not real gold.

For a full breakdown of what each color means karat-by-karat, see our Gold Acid Test Colors Explained guide.

Step 5: Confirm With a Lower or Higher Karat Acid

If the streak faded with 14K acid, test a fresh streak with 10K acid. If 10K also dissolves the streak, you're likely looking at gold plate or a non-gold base metal. For tips on testing silver or platinum pieces you may encounter, check out our guide on how to test silver and platinum at home.

Step 6: Neutralize and Clean Up

Apply a baking soda and water paste to the stone and any drips. Rinse with water. Wipe acid droppers clean, cap bottles tightly, and store safely.

Reading Your Results: Color Reaction Chart

Reaction on Stone What It Means Likely Material
No change — streak stays bright gold Real gold at or above tested karat 10K–24K gold
Slow fade (30+ seconds) Slightly lower karat than tested One step below (e.g. 10K tested with 14K acid)
Milky / cream color Gold-filled or heavy gold plate Gold-filled / rolled gold
Green Not real gold Brass or low-quality base metal
Brown Not real gold Copper or bronze alloy
Rapid dissolve (under 5 seconds) Far below tested karat or fake Costume jewelry / plated metal

Accuracy Tips the Pros Use

  1. Always make a fresh streak for each acid test. Residue from a previous test will skew results.
  2. Use fresh acid. Nitric acid weakens over 12–18 months once opened. Replace solutions annually for best accuracy.
  3. Test multiple spots on the same piece — plated jewelry often passes one test but fails another.
  4. Cross-check with a magnet. Real gold is not magnetic. Any magnetic pull means base metal is present.
  5. Consider an electronic tester for high-value pieces. Acid testing is excellent for screening; electronic testers add confirmation without damaging the item.

Common Mistakes to Avoid

  • Skipping the stamp check. Always look for a karat hallmark first to choose the right starting acid.
  • Testing plated jewelry on the surface only. File a small notch through the plating to test the base metal underneath.
  • Using too much acid. One drop is plenty. More acid does not mean more accurate results.
  • Reading too late. The reaction is most reliable within the first 20 seconds.
  • Reusing droppers. Cross-contamination ruins accuracy.

When to Send a Piece to a Professional

Acid testing is highly reliable for screening, but you should send a piece to a certified assayer when:

  • The piece is valued over $2,000
  • You suspect a sophisticated counterfeit (tungsten core, gold-plated platinum)
  • You're buying scrap in bulk and need a documented assay
  • Insurance or estate paperwork requires it

For pawn shop professionals, combining acid testing with electronic verification provides the fastest and most reliable authentication workflow.

Frequently Asked Questions

Is nitric acid testing safe for the jewelry?

When done on the testing stone (not the jewelry directly), the piece itself is unharmed. Only the small streak transferred to the stone reacts with the acid.

How accurate is the nitric acid test?

Properly performed, nitric acid testing is 95%+ accurate for distinguishing real gold from fakes and identifying karat within one step (10K, 14K, 18K, 22K).

How long does nitric acid last?

Sealed bottles last 6 months. Once opened, replace within 3 months for best accuracy.

Can I test white gold the same way?

Yes. White gold reacts the same way as yellow gold on the testing stone. The rhodium plating on most white gold pieces is thin enough that the streak captures the underlying alloy.

What's the difference between nitric acid and aqua regia testing?

Nitric acid solutions test up to 22K. For 24K (pure gold), you need aqua regia (a mix of nitric and hydrochloric acid), included in our advanced kits.

Ready to Test Like a Pro?

Every True Assay gold testing kit includes premium nitric acid solutions, a basalt testing stone, and a step-by-step quick-reference card so you can test confidently from day one. Whether you're a pawn shop, jewelry reseller, or collector, accurate testing protects your money and your reputation.

Use code NITRIC10 at checkout for 10% off your kit.

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