When you walk into a gold buyer, one of the first things they do is test your jewelry to determine its karat. How they do that test directly affects the offer you receive. There are two methods in common use — acid testing and XRF analysis — and the difference between them is significant.
Acid Testing: The Old Method
Acid testing has been used to evaluate gold for over a century. The process works like this:
- The buyer rubs the jewelry across a black touchstone, leaving a streak of metal
- They apply nitric acid of a specific concentration to the streak
- They observe how the streak reacts — whether it dissolves, changes color, or remains
- Based on the reaction, they estimate the karat
The key word is "estimate." Acid testing is inherently approximate. A buyer testing a piece that reacts somewhere between a 14K and 18K standard may call it 14K to be safe — meaning they pay you for 14K gold when you may actually have 18K. On a 20-gram piece, that difference is roughly $80–$120 in cash.
Acid testing also destroys a small amount of material (the streak from the touchstone) and can miss alloys — gold-plated items can pass lower-karat acid tests if the plating is thick enough.
XRF Analysis: The Refinery Method
XRF stands for X-ray fluorescence. An XRF analyzer fires X-rays at the surface of a piece of metal. The metal absorbs those X-rays and then emits its own fluorescent X-rays at wavelengths specific to each element. The machine reads those emission wavelengths and produces a precise elemental breakdown: "this piece is 58.2% gold, 28.4% silver, 13.4% copper."
That result maps directly to karat: 58.3% gold = 14K. 75.0% = 18K. The reading is accurate to within fractions of a percent, takes about 30 seconds, and requires no physical contact with the piece.
XRF is the standard in refineries and large-scale precious metals processing because it eliminates estimation error. The same technology that refineries use to process tons of scrap metal is what YML Refinery uses on your gold bracelet.
Why This Matters for Your Offer
Consider a scenario: you have a gold necklace stamped "750" (18K). The clasp has a small amount of solder that is lower karat. An acid tester may test the clasp area and offer you 14K price on the whole piece. An XRF machine tests the body of the necklace separately and correctly identifies it as 18K — you receive the higher offer on the correctly-identified portion.
Another scenario: your grandmother's ring is stamped "14K" but was stamped that way in an era of looser quality control — it may actually be 12.5K or 15K. Acid testing may approximate it correctly or may not. XRF tells you exactly what's there.
A third scenario: you have a white gold piece. White gold is yellow gold alloyed with palladium, nickel, or zinc and often rhodium-plated. Acid testing white gold is genuinely difficult — the rhodium plating resists acid. An experienced buyer will file through the plating first, but less careful buyers may acid-test the surface and undervalue the piece. XRF reads straight through the plating to the alloy underneath.
What to Ask Before You Sell
Before accepting an offer from any gold buyer in Arizona, ask: "How are you testing my gold?"
If the answer is acid testing, that's not necessarily a dealbreaker — experienced buyers with acid testing can be accurate. But you should understand that the offer is based on an estimate, not a measurement. If anything you're selling is high-karat (18K, 22K, 24K), platinum, or has complex alloys, the estimation risk is higher.
If the answer is XRF, you're getting a precise measurement. The offer should reflect exactly what's in the piece.
The Transparency Difference
At YML Refinery near Scottsdale, we test every piece with XRF in front of you and show you the readout. You see the exact karat and weight before we make an offer. We then apply the live spot price (visible on the screen at kitco.com) and calculate your offer on the spot. There's no estimation, no guessing, and no reason to take our word for it — you watch the math happen.
This transparency is unusual in the industry. Most buyers don't show you their test results. We do, because accurate testing and visible math is how you build a reputation in a market where a lot of buyers compete on opacity rather than quality.
The Bottom Line
XRF testing benefits sellers in three ways:
- Accuracy — you're paid for what you actually have, not an estimate
- Transparency — you see the result, not just hear a number
- Higher offers on high-karat pieces — 18K and 22K items are correctly identified, not conservatively estimated down
If you're selling gold near Phoenix, Mesa, or anywhere in the Phoenix metro, the testing method your buyer uses affects your payout. YML Refinery is at 11115 Grand Ave #4, Youngtown — call (623) 974-3772 or walk in Mon–Sat 9am–5pm.
Also see: how we price every gold offer and what to bring when selling gold in Arizona.