Occasionally, you may come across shiny metal scrap that looks valuable, but it can be difficult to determine its worth. Testing it with acids may not be possible or desirable in your home or shop. Is there a simpler way to identify precious metals? Absolutely! In the following steps, I will show you how to test metals using minimal equipment and without the use of harsh acids. This method is safe to use in any setting.
These instructions will help you build a DIY device that distinguishes between Precious Metals and Base Metals using the Redox Series of metals principle, commonly used in refining and acid experiments. This effect has been long-known, discovered by Galvani and Volta 250 years ago while conducting research that led to the invention of the modern battery. As an electrical engineer, I applied Galvani's principle to create this device.
Save to use even when children are around. Try it out for yourself!
Here is how it goes:
Equipment needed:
Step 1: Prepare a glass or spraybottle with clean distilled water.
Step 2: Take a small flat sheet of copper, preferably pure 999 Copper. Clean it with alcohol to remove any grease or glue, then rinse with distilled water. Avoid using aggressive chemicals like acid or alkaline cleaners.
Step 3: Use a clean white cotton cloth, or a clean tissue or a white piece of paper. A piece of newspaper would also do the job but is not ideal. Avoid any cloth with grease, metal chips, or dust. Place the cloth on the Copper sheet or object, leaving a small area or corner uncovered.
Step 5: Wet the cloth with the prepared solution. Do not wet the uncovered area. The cloth should be wet but not swimming in water. Just so that it is wet and water is not dripping from the cloth, or at least not much.
Step 6: Put another piece of Copper on top of the cloth, preferably known pure Copper. It can be Copper-plated as well, so most cent coins are plated in more or less pure Copper. For our purpose, they will do the job. It would be great if you have any known pure metal samples readily available for testing the test setup.
Step 7: Use a multimeter and set the voltage type to "DC." Set the range of the multimeter to 2V if possible or below, down to 1V or 1000mV. Connect the - probe (usually black, often labeled "Ground") to the uncovered, dry corner of the copper sheet or Copper object beneath the cloth, and the other probe (usually red) to the Copper object on top of the cloth. Your multimeter, whether digital or analog, should react a little bit for a short moment, then remain at around 0V, let´s say -30 mV to +30 mV. If there is a calibration button on your multimeter, use it to set it to zero.
Step 8: Take the object that you want to test and put it on top of the (still wet!) cloth. Repeat Step 7 in the same way: the black -probe to the clean dry edge of the Copper underneath and the + or red probe to the object you want to test. You can use scotch tape to attach the probe to the Copper sheet. That way one hand remains free.
If your multimeter reads above 50mV, around 100mV, it indicates a Precious Metal. A negative voltage, such as -100mV, suggests a Base Metal. Below: 999 Gold and molten e-waste from Palladium and Silver loaded MLCC capacitors.
Note that this method only detects metals on the surface of an object. Gold-plated items may show up as Precious Metals even if the core is cheap Base Metal, while a molten metal with 5% Platinum may be detected as Base Metal. This DIY method is useful for detecting Precious Metals if they are present in a considerable amount or as plating on the surface, but it's not comprehensive for all metal detection questions.
The screenshot shows the XRF analysis of the previously tested unknown material, revealing a mix of Palladium, Silver, Gold, Copper, and other Base Metals.
To ensure accurate results, keep the cloth damp but not too wet. A dry cloth will not work correctly and may lead to confusing results. Change the cloth after a few tests to avoid contamination to it from Base Metals. Temperature and humidity can affect the results, so perform the test at room temperature for the best outcome. This method is a quick, non-destructive tool suitable for testing jewelry and other items without the need for a scratch or acid test, although results may not always be accurate.
Here are some additional test results from the setup. Note that your results may vary depending on so many factors that it makes no sense to try to compensate them in such a low-cost solution. It is only important to check for the polarity of the result or how close it is to 0 V. Note that the Precious Metals always have a positive voltage reading whereas the base Metals return a negative voltage.
Perform a calibration run before testing using Copper and a well-known Precious Metal like Fine Gold to ensure probes are in order. Note the results and compare them with known samples when testing an unknown object to determine the metal type. Replace the cloth frequently for conclusive and repeatable results since the setup's chemical composition changes with each test.
Note that the results may vary depending on how the probe contacts the metal, especially for alloys or molten samples. This type of test cannot provide quantitative statements or determine the ratio of metals in the sample.
My Project, the BozzTech MTI00X Metal Tester which I developed is based on this Redox principle. It compensates for these variables, and it offers a more convenient and repeatable assessment by displaying results in a graphical format on a PC screen, using AI technology among other benefits.
Enjoy and try this at home!
Marcel
Source: Taken from the book: M. A. Buth "Gold from Scrap", 2023 fully revised edition. Available on Amazon.
These instructions will help you build a DIY device that distinguishes between Precious Metals and Base Metals using the Redox Series of metals principle, commonly used in refining and acid experiments. This effect has been long-known, discovered by Galvani and Volta 250 years ago while conducting research that led to the invention of the modern battery. As an electrical engineer, I applied Galvani's principle to create this device.
Save to use even when children are around. Try it out for yourself!
Here is how it goes:
Equipment needed:
Step 1: Prepare a glass or spraybottle with clean distilled water.
Step 2: Take a small flat sheet of copper, preferably pure 999 Copper. Clean it with alcohol to remove any grease or glue, then rinse with distilled water. Avoid using aggressive chemicals like acid or alkaline cleaners.
Step 3: Use a clean white cotton cloth, or a clean tissue or a white piece of paper. A piece of newspaper would also do the job but is not ideal. Avoid any cloth with grease, metal chips, or dust. Place the cloth on the Copper sheet or object, leaving a small area or corner uncovered.
Step 5: Wet the cloth with the prepared solution. Do not wet the uncovered area. The cloth should be wet but not swimming in water. Just so that it is wet and water is not dripping from the cloth, or at least not much.
Step 6: Put another piece of Copper on top of the cloth, preferably known pure Copper. It can be Copper-plated as well, so most cent coins are plated in more or less pure Copper. For our purpose, they will do the job. It would be great if you have any known pure metal samples readily available for testing the test setup.
Step 7: Use a multimeter and set the voltage type to "DC." Set the range of the multimeter to 2V if possible or below, down to 1V or 1000mV. Connect the - probe (usually black, often labeled "Ground") to the uncovered, dry corner of the copper sheet or Copper object beneath the cloth, and the other probe (usually red) to the Copper object on top of the cloth. Your multimeter, whether digital or analog, should react a little bit for a short moment, then remain at around 0V, let´s say -30 mV to +30 mV. If there is a calibration button on your multimeter, use it to set it to zero.
Step 8: Take the object that you want to test and put it on top of the (still wet!) cloth. Repeat Step 7 in the same way: the black -probe to the clean dry edge of the Copper underneath and the + or red probe to the object you want to test. You can use scotch tape to attach the probe to the Copper sheet. That way one hand remains free.
If your multimeter reads above 50mV, around 100mV, it indicates a Precious Metal. A negative voltage, such as -100mV, suggests a Base Metal. Below: 999 Gold and molten e-waste from Palladium and Silver loaded MLCC capacitors.
Note that this method only detects metals on the surface of an object. Gold-plated items may show up as Precious Metals even if the core is cheap Base Metal, while a molten metal with 5% Platinum may be detected as Base Metal. This DIY method is useful for detecting Precious Metals if they are present in a considerable amount or as plating on the surface, but it's not comprehensive for all metal detection questions.
The screenshot shows the XRF analysis of the previously tested unknown material, revealing a mix of Palladium, Silver, Gold, Copper, and other Base Metals.
To ensure accurate results, keep the cloth damp but not too wet. A dry cloth will not work correctly and may lead to confusing results. Change the cloth after a few tests to avoid contamination to it from Base Metals. Temperature and humidity can affect the results, so perform the test at room temperature for the best outcome. This method is a quick, non-destructive tool suitable for testing jewelry and other items without the need for a scratch or acid test, although results may not always be accurate.
Here are some additional test results from the setup. Note that your results may vary depending on so many factors that it makes no sense to try to compensate them in such a low-cost solution. It is only important to check for the polarity of the result or how close it is to 0 V. Note that the Precious Metals always have a positive voltage reading whereas the base Metals return a negative voltage.
Perform a calibration run before testing using Copper and a well-known Precious Metal like Fine Gold to ensure probes are in order. Note the results and compare them with known samples when testing an unknown object to determine the metal type. Replace the cloth frequently for conclusive and repeatable results since the setup's chemical composition changes with each test.
Note that the results may vary depending on how the probe contacts the metal, especially for alloys or molten samples. This type of test cannot provide quantitative statements or determine the ratio of metals in the sample.
My Project, the BozzTech MTI00X Metal Tester which I developed is based on this Redox principle. It compensates for these variables, and it offers a more convenient and repeatable assessment by displaying results in a graphical format on a PC screen, using AI technology among other benefits.
Enjoy and try this at home!
Marcel
Source: Taken from the book: M. A. Buth "Gold from Scrap", 2023 fully revised edition. Available on Amazon.
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