Know your material
Pure copper or just a copper finish?
C10100. At least 99.99% copper. A material grade with specific requirements you can check.
A buyer’s evidence checklist
| Evidence | What it can establish | What it cannot establish alone |
|---|---|---|
| A serial number | Which item a seller record refers to | That the metal meets a composition specification. |
| A certificate of authenticity | The issuer’s stated identity, grade and traceability claims | An independent assay unless its supporting analysis is supplied. |
| A handheld XRF reading | Many detectable elements near the tested surface | Bulk homogeneity, every trace impurity or the C10100 oxygen limit. |
| Supplier or laboratory report | The measured elements and sample, within stated method limits | That an unrelated bar or batch has the same composition. |
Use these questions alongside the copper-bar purchase checklist. If you are comparing an object’s retail price with metal value, read the copper price and unit-conversion guide.
See also: Copper bar 1 kg — Brushed Bar
You buy a copper bar for the metal, its weight and the feeling of owning something substantial. You should also be able to understand what you are getting. “Pure copper”, an attractive stamp or a long string of nines is not enough to document its composition.
We chose C10100 for Coppervm bars because material quality matters to us. Here we explain what the designation means, examine a reported case of mislabelled raw materials, and set out the questions that help you assess a purchase.
C10100: quality with specific requirements
C10100 is oxygen-free electronic copper, also known as OFE. According to the Copper Development Association’s material data, it requires at least 99.99% copper, excluding silver, and no more than 0.0005% oxygen — five parts per million. The grade also limits a range of other impurities.
That is why C10100 tells you more than “pure copper” alone. It defines a composition against which supplier documentation and relevant analyses can be assessed. The designation itself, however, is not a test of an individual bar.
99.9%, 99.99% and all those extra nines
Purity is commonly expressed as a percentage or in parts per thousand. A fineness of 999 means 99.9%, while 999.9 means 99.99%. Decimal places matter, but they do not make a listing more credible without an analysis that supports that precision.
More nines can describe a real, high-purity material. Still, ask how the value was established: Which elements were measured? How small a quantity can the method detect? Which batch does the result apply to? A rounded number on an instrument display does not automatically answer those questions.
When the “copper” turned out to be plated steel
In March 2026, Roman Hartung, known as der8auer and associated with Thermal Grizzly, described raw material purchases from two suppliers found through Alibaba. According to his account, material sold as copper turned out to be copper-plated steel. Conductivity checks and magnetic attraction were among the tests that exposed the problem. The case was covered by VideoCardz on 8 March 2026, which links to Hartung’s own account, “I Got Scammed”.
This case involved industrial raw materials. It does not establish how common the problem is among copper bars sold to individual buyers, or that Alibaba suppliers are generally unreliable. Our takeaway is straightforward: A surface that looks right and an established seller profile cannot replace checks on the material actually delivered.
What does a magnet test actually tell you?
Pure copper and ordinary brass are not noticeably attracted to an ordinary magnet. Brass is primarily an alloy of copper and zinc. The Copper Development Association’s material guide describes copper and copper alloys as generally nonmagnetic.
- The magnet clearly sticks to the metal itself: This is a warning sign if the item was sold as solid, pure copper. Copper-plated ordinary steel is one possible explanation.
- The magnet does not stick: This is consistent with copper, but also with brass and other materials. It confirms neither the metal type nor its purity.
The test therefore cannot distinguish pure copper from brass. Check the bar itself; metal parts in packaging or a case can affect your impression. A magnet is a simple first check, not a certificate of authenticity.
XRF is useful — when you understand what it measures
XRF, or X-ray fluorescence, is used to examine which elements a material contains. It can, for example, help distinguish copper from a copper–zinc alloy. But the surface and the structure of the sample affect the reading. A coating can make the result unrepresentative of the core. Instrument manufacturer Evident explains this in its guide to XRF and material identification.
A typical handheld XRF reading also cannot document the very low oxygen content required for C10100. Evident describes the limitations for light elements in its XRF guide. Fully documenting the grade requires analyses and material records that cover the relevant requirements.
If there is reason to suspect the wrong material, a qualified laboratory should choose an appropriate combination of examinations. Weight, dimensions and conductivity can provide useful information, but no simple home test can establish 99.99% purity.
Four questions before you buy
- What is the material grade? Ask for a specific designation, such as C10100, and the purity that is guaranteed.
- Which material does the documentation cover? A material certificate or analysis report should be traceable to the batch used to make the product.
- What has actually been tested? Look for the method, results, date and who performed the analysis. Clarify whether the checks cover the batch or the individual bar.
- How does the documentation stay with the product? Serial numbers and batch details make it easier to connect a bar to its supporting records.
A seller’s certificate of authenticity and an independent laboratory report serve different purposes. A certificate can identify the product and bring together information about it. The underlying analysis and traceability determine what it documents. The same applies to terms such as “verified” and “tested”: Ask what they mean in practice.
Our material choice: C10100
Coppervm bars are made from C10100 copper. They come with a unique serial number and a signed certificate of authenticity (COA). XRF forms part of the material checks. We distinguish between the raw material specification, what a measurement can show, and the documentation supplied with the bar.
Would you like to know more about the checks or documentation before deciding? Contact us. Ask about a specific product or batch, and we can explain the basis for the information provided.
If you are selling copper in Norway, purity is only one part of the price. Our guide explains the difference between metal value and a yard’s quote: copper price per kg and scrap payouts in Norway.