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Singer oil

Hi to All!
About singer oil, what is index refraction?
Many regards!

If singer oil is a light machine oil for sewing machines, the RI is about 1.47. If you pull up a table of RIs of oils, you will find most mineral and vegetable oils at about 1.47 to 1.49. There are some other aromatic oils like clove oil and cassia oil which are higher, around 1.51 to 1.55. Any of these will help with finding flaws in submerged gems. The most typical immersion fluid which is not toxic and is even used medicinally is benzyl benzoate, which can be fairly cheaply on ebay…probably under $20 for 4 to 8 ounces? -royjohn

Thanks Roy!!!