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I am looking to sharpen a knife, and i seem to be out of oil... Is there a quick hack or home substitute i could use for this? I have 3-in-1 oil (white bottle) but aside from that (in terms of tool oil) all i have is the standard home/cooking stuff, Vegetable, Mineral, Olive, etc.

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    3-in-1 or mineral oil should work for oilstones. I wouldn't use a vegetable oil, and certainly not a drying oil. – keshlam Jul 20 '16 at 11:40
  • The 3-in-1 was what i was hoping to hear. – grmartin Jul 20 '16 at 11:45
  • Water. I'm not an expert and I really don't know about oil stones but, for my restaurant, we all use stones soaked in water and would never use oil. It's something taught to me by a couple of chefs long ago. – Rob Jul 20 '16 at 11:48
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    Water stones are a different composition from oil stones. Either can work, but don't confuse them. – keshlam Jul 20 '16 at 15:44
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I regularly use 3-in-1 on my oilstones, to no ill effect. A commercial honing oil is thinner, but as long as it can float the metal particles, you're good. You can clean some out with a spray of WD-40, if it's starting to fill up.

(The knife aficionados are going to hate this answer. It's got 3-in-1 and WD-40 in the same paragraph.)

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Most commercial honing oils are heavy "naphthenic" oils and "light" mineral oil. Which basically means a thinned (mixture of) oil(s).

The weight of mineral oil is a matter of carbon chain length. The longer the chain, the heavier and thicker (more viscous) the oil is. Now, mineral oil comes from petroleum. Honing oil is not like food grade mineral oil (which is comparable in viscosity, but has chain length of about 29 carbons; whereas vegetable oils have carbon lengths of usually 12 - 18 carbons).

Honing-mineral oil is lighter in viscosity and has shorter chains than food grade mineral oil (like 17 - 27 carbons). And naptha, technically isn't really an oil at all (again, oils are chains of carbons). Naphtha looks like a figure 8, of carbons. But heavy naphthenic oils would be a slurry of naphtha and other substances with similar boiling points.

However, I've seen people use spit, grape jelly, tongue oil, 3-in-1, baby oil, used motor oil, and used transmission fluid to sharpen blades. So, I suppose it doesn't matter very much what you use... but I would recommend oils derived from petroleum, especially because (besides being more viscous than good honing oil) vegetable oils contain fatty acids, which can incite rusting (not as bad as saliva though). With all that being said, viscosity is probably the next most important characteristic.

If I were making a commercial or professional use honing oil, I would aim for a viscosity like that of commercial blends (about 9 centistokes at 40°C). Again, commercial blends are a mixture of heavy naphtha (viscosity of about 0.55 centistokes at 40°C) light mineral oil with a nominal viscosity of 70 (or 12.61 cStokes at 40°C). Note: the nominal viscosity of mineral oil (70-355) is nothing like motor oil (eg 10W30 has viscosity of about 64 cSt at 40°C... at 100°C it's about 10 cSt).

Baby oil has a nominal viscosity of about 72 (or 13 cStokes at 40°C). Naphtha for lighers has a viscosity of about 0.3 cStokes at 40°C. Mixing different weights might achieve a similar effect... but if you could use something else having a viscosity in between 0.3 cSt and 13 cSt (at 40°C), I think it would work a little better. So, for what it's worth, kerosene (defined as 10 - 16 carbon chain molecules) has a viscosity of 1.46 cSt @ 40°C and deisel has a viscosity of about 7.9 @ 40°C.

The viscosity of one particular base for a commercial honing oil (ingredients are listed as Mineral oil, Petroleum Distillates- Hydrotreated, and (mild) Light Naphthenic) is listed at 9.15cSt.

So, I would try a mixture like:

  • 6 parts baby oil (13cSt)
  • 2 parts naphtha for lighters (0.3cSt)
  • 1 part deisel- 1D grade fuel (1.46cSt, very rough average)
  • 1 part kerosene (7.9cSt)

Mathematically estimating the viscosity: (6x13 + 2x0.3 + 1.46 + 7.9)/10 = (roughly) 8.8 cSt. This is not really the way to determine viscosity (which depends on density of the liquids... in this example, it's being ignored), but it should be close (like within 10%).

  • Well I never thought much about the chemical science of it. This is quite enlightening. Thank you. – grmartin Jul 20 '16 at 16:27

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