Do I use water, oil or nothing on a sharpening stone?
What the lubricant is actually doing, why oil on a water stone ruins it permanently, and the honest answer about diamond plates.
- Difficulty
- beginner
- Time
- 10 min
- Read
- 4 min
Short answer
Use whatever the stone was designed for and never mix them. Water stones take water only. Oil stones — Arkansas, India, Crystolon — take honing oil, and once oil has soaked into a stone you cannot go back to water. Diamond plates work best with water or a drop of washing-up liquid in water, and they can be used dry at a cost in clogging and heat.
The lubricant on a stone is not there to make things slippery. Its job is to float the swarf — the metal particles the stone is removing — clear of the abrasive surface, so the grit keeps cutting rather than becoming packed and polished. That explains every rule below, including why using the wrong liquid ruins a stone.
Step by step
- Understand the mechanism first.As a stone cuts, it produces fine steel particles. If they stay on the surface they fill the gaps between the abrasive grains, and a loaded stone stops cutting and starts burnishing. The liquid suspends and carries those particles away. That is the whole function.
- Water stones: water only.Japanese-style water stones are a soft binder that releases fresh grit as it wears, so they cut fast. Some are soaking stones that live in water; most modern ones are splash-and-go, wetted from a spray bottle as you work. Keep the surface visibly wet, and rinse the slurry off between grits so a coarse grit does not contaminate a fine stone.
- Oil stones: honing oil only.Natural Arkansas stones and manufactured India and Crystolon stones are dense and hard, and they use a thin oil to float the swarf. Use a proper honing oil or a light mineral oil — not vegetable oil, which goes gummy and rancid, and not thick engine oil, which is too viscous to carry particles away.
- Never put oil on a water stone.It soaks into the porous binder and cannot be removed. The stone then will not accept water, will not release slurry, and cuts far more slowly for ever. This is the single most common way a good stone is ruined.
- Diamond plates: water, or dry if you must.A little water, or water with a drop of washing-up liquid, keeps the swarf moving and the plate cutting. They can be run dry, and many people do, but they clog faster and generate more heat. Never use oil on a diamond plate — it holds the swarf against the surface.
- Ceramic stones: water or dry.Fine ceramic hones can be used dry for touch-ups and with water for longer work. They load quickly when dry and need cleaning with an abrasive block or a scouring pad.
- Clean a loaded stone.A stone that has stopped cutting is often loaded rather than worn. Water stones: flatten the surface, which exposes fresh grit. Oil stones: scrub with paraffin or white spirit and a stiff brush. Diamond plates: a scouring pad and soapy water.
- Store them properly.Dry water stones fully before boxing them, and never let any stone freeze — trapped water expands and shatters the stone. Keep oil stones in a closed box so they do not collect dust that then embeds in the surface.
- Do not overthink the liquid.Water is water. Purpose-sold honing oil is convenient but a light mineral oil does the same job. What matters is using the right category for the stone and keeping the surface clean.
Tips
- Sharpen over a tray or a sink. Both water and oil sharpening make a mess, and a set-up that makes a mess is one that does not get used.
- A cheap spray bottle beside the stones is the difference between a splash-and-go water stone being convenient and being a chore.
- If you inherit an old oil stone that is glazed and black, soak it in paraffin overnight and scrub it. Many recover completely.
- Slurry on a water stone is doing useful work — it is fine abrasive. Do not rinse it away mid-grit, only between grits.
Questions people ask
Can I use water on an oil stone?
On a new, never-oiled one, yes — some India stones are sold to be used either way. Once a stone has had oil in it, water sits on the surface and does nothing useful.
Is honing oil different from ordinary oil?
It is simply a light, non-gumming mineral oil. Proprietary honing oil is convenient and cheap; a light machine oil or food-grade mineral oil does the same job. Avoid anything vegetable-based, which polymerises and clogs the stone.
Do I need to soak my water stone?
Only if it is sold as a soaking stone — usually the softer, coarser ones. Most modern water stones are splash-and-go and are damaged by permanent soaking. Check what the maker says.