The short answer
Yes, and so does almost every fake. Brass is 8.4 times heavier than the same amount of water, so it drops to the bottom of the glass just like gold. The water test only tells you a piece is heavier than water. To catch brass, weigh the piece in and out of water on a jewelry scale. 14K yellow gold comes out near 13, and brass near 8.4.
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The water test sounds easy. Drop the piece in a glass, and if it sinks, it’s gold.
It will sink. Brass sinks too, and so do copper and aluminum. Under a January 2026 post titled “Gold or brass,” about a pendant stamped 14k that sank in water, one commenter replied: “Anything that’s denser than water sinks in water.”1
Why everything sinks
Anything heavier than the same amount of water sinks, and every metal in your jewelry box is heavier.2
| Metal | Times heavier than water |
|---|---|
| 24K gold | 19.36 |
| 18K yellow gold | 15.58 |
| 14K yellow gold | 13.07 |
| 10K yellow gold | 11.57 |
| Sterling silver | 10.40 |
| Copper | 8.94 |
| Brass | 8.40 |
| Aluminum | 2.70 |
Even a gold dealer’s guide that still lists the float test admits it “does not catch solid brass.”3
The chain that passed five home tests
In October 2025, someone posted a chain from a grandmother who loved yard sales. It had no stamp, and it had passed five home tests. A magnet didn’t grab it, vinegar did nothing, it left a black line through foundation makeup, its streak survived 10k acid, and it sank (“it’s heavy, so it sank to the bottom”).
The poster still had doubts, and commenters said to file a tiny notch and test underneath. In the notch, 14k acid foamed green. One commenter read that as a copper alloy like brass, and another had already called the chain “base metal gold plated.”4 Nobody ran a machine test, so treat that as the thread’s opinion. Still, five home tests said gold, and the people who looked closer thought it was plated.
Put the glass on a scale
The same glass of water becomes a real test once you put it on a scale. You need a jewelry scale that reads to a hundredth of a gram.3
- Weigh the piece dry. Call that A.
- Put a cup of water on the scale and press tare.
- Hang the piece on a thread so it sits fully underwater, without touching the sides or the bottom. The reading is B.
- Divide A by B.
Step 3 gives you the weight of the water your piece pushes aside, so A divided by B tells you how many times heavier than water the piece is.5 A ring that weighs 6.5 g dry and reads 0.50 g in step 3 comes out at 13, which fits 14K yellow gold. If it reads 0.77 g, it comes out at 8.4, and that’s brass.
It only works on solid metal. Stones, hollow parts, and air trapped in chain links throw it off.6 It also can’t separate close karats like 14K and 18K.5 But it does catch brass.
The next step
If the scale says gold, read the stamp next with the four stamp checks and my hallmark chart. If real money depends on it, ask a gold buyer for an XRF reading. It’s a machine test that leaves no mark, and some buyers do it free.3
Chapter twelve of my book goes through the kitchen-table tests that work and the ones to skip. You can read chapter one free.
Sources
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“Gold or brass,” r/Gold, January 16, 2026, reddit.com/comments/1qe62b5. The quoted reply is a commenter’s; the poster added that the pendant had a 14k stamp. Several commenters judged it brass from the photos; nobody in the thread reports a test. ↩
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Stuller, “Where can I find the specific gravity of various materials?,” August 15, 2012, stuller.com. Stuller is a U.S. jewelry manufacturer and bench supplier; all figures in the table are from its chart, which defines specific gravity as density compared with water’s. ↩
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US Gold and Coin, “How to Tell If Gold Is Real: 8 At-Home Tests That Work,” April 30, 2026, usgoldandcoin.com. The guide lists the float test as one of its eight; the “does not catch solid brass” line, the 0.01-gram scale, and the free in-office XRF testing are all from the same page. (A gold dealer’s guide; its density figures match Stuller’s.) ↩ ↩2 ↩3
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“Did 5 at-home tests. All positive for gold but I’m not convinced.,” r/Gold, October 26, 2025, reddit.com/comments/1ogarg1. The five tests, the quoted water-test line, and the filed-groove result are the poster’s; the “copper alloy base metal, like brass” reading and the “base metal gold plated” verdict are two commenters’. No XRF or lab test is reported. ↩
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Quicktest, “Testing precious metals using specific gravity (relative density),” quicktest.co.uk: a cube of water 1 cm on each side weighs 1 g; alloys have overlapping ranges, which “can make it difficult to distinguish between 14ct and 18ct”; the method “cannot distinguish 9ct from copper.” Quicktest makes metal-testing kits. ↩ ↩2
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Method and limits as given in A Trained Eye to Spot a Treasure, chapter twelve, after PawkBroker, “How to Test Gold at Home,” February 2026, and Metalorix, “Specific Gravity Testing,” March 2026. Quicktest’s page (note 5) adds that the piece “must be homogenous,” one metal only, with no gemstones. ↩