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<p>[QUOTE=&quot;antique85, post: 4396300, member: 7651&quot;]I am new to gold testing and bought a natural obsidian stone for scratch acid testing. I find it really time consuming to clean the scratches off the stones. What do you use? Following the youtube videos instructions, I have been using a paper towel with water. But someone suggested soap could also be used. And this GIA article recommend 320 grit sandpaper &quot;<a href="https://www.gia.edu/bench-tip-use-the-touchstone-method-for-testing-purity-karat-gold" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://www.gia.edu/bench-tip-use-the-touchstone-method-for-testing-purity-karat-gold" rel="nofollow">https://www.gia.edu/bench-tip-use-the-touchstone-method-for-testing-purity-karat-gold</a>&quot;:</p><p><br /></p><p>&quot;Remove the metal from the stone’s surface by placing it facedown on a piece of 320-grit abrasive paper on a flat surface. Apply moderate pressure and sand it in a circular motion until sample layers are no longer visible. Neutralize, rinse and blot dry before replacing in the kit.&quot; </p><p><br /></p><p>Has anyone used sandpaper?</p><p><br /></p><p>The above GIA article also recommends something I did not see on any gold testing youtube videos--perhaps I don&#039;t understand it.&nbsp; It seems to say after using the acid, put the touchstone in a mixture of baking soda and water before evaluating the results:</p><p><br /></p><p>&quot;Now choose the bottle labeled for testing 10k and lightly swipe the applicator across all the samples.</p><p>• After approximately 20 to 40 seconds, place the touchstone in a mixture of baking soda and water to neutralize the acid in one beaker, then rinse in water in the other beaker.</p><p>• Blot the touchstone with paper towels and observe. The 10k sample has dissolved....&quot;[/QUOTE]</p><p><br /></p>

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