Lubricating fluids for sharpening

Since ancient times, the first sharpeners of the world used oil for sharpening. Sources describing the use of Cretan stone in Ancient Greece mentioned its use with "wooden" oil. Over the past centuries, a wide variety of liquids have been used to improve the sharpening process, technologies have changed and new developments have appeared.
The lubricating fluid reduces the hardenability of the stone during operation and prevents the blade from overheating during sharpening, although with manual sharpening, creating a temperature dangerous for the cutting edge is almost impossible.

Lubricating fluids are used for several types of stones: stones made of silicon carbide, aluminum oxide, various natural stones, diamond bars (primary bars on organic bond and OSB bond).  

The main criteria for a good sharpening oil are slow drying, as well as a low rate of its thickening. Besides, safety is an important factor. The oil should be safe for internal organs when inhaled during operation and non-toxic to the skin of the sharpener's hands, and it should not cause allergies.

To the non-drying oils include castor, olive, peanut, rapeseed, coleseed, mustard, coffee, clove. In addition, the so-called lamp oil can be used.  The main problem with this liquid is that it can "clog" the surface of the stone and can cause an allergic reaction in the sharpener. Johnson's Baby oil, which is based on vaseline oil, is prevalent among sharpeners, but its density does not make it possible to work comfortably, and it is diluted for sharpening with oleic oil, as well as orange oil, which dilutes even more.  

The most optimal for sharpening can be considered the water-based and the oleic acid-based oils.

Oleic acid (cis-9-octadecenoic acid) CH3(CH2)7CN=CH(CH2)7COOH is a monounsaturated fatty acid. It belongs to the group of omega-9 unsaturated fatty acids. It is an oily liquid, lighter than water, colorless and odorless, insoluble in water, but soluble in organic solvents. The basis of oleic acid is Omega-9-unsaturated fatty acids or ω-9 fatty acids — a family of unsaturated fatty acids. Several ω-9-unsaturated fatty acids are components of both animal fats and vegetable oils. Omega-9-unsaturated fatty acids are not essential fatty acids (essential), unlike the Omega-3-unsaturated fatty acids and Omega-6-unsaturated fatty acids classes. Omega-9 acids can be synthesized by the human body from unsaturated omega-3 and omega-6 fatty acids. Two acids ω-9-often used for industrial purposes:

1. Erucic acid - is a part of rapeseed oil, wallflower seeds, and mustard seeds. Rapeseed oil is used in cooking, for the manufacture of margarine, in the steel, soap, leather, and textile industries, as well as to obtain a varnish.

2. Oleic acid is the main component of olive oil, macadamia oil, and other monounsaturated fats.

Oleic acid is found in many animal fats in the form of glyceride esters: beef fat (41-42 %), pork fat (37-44 %), cod fat (30 %), and is also found in many vegetable oils: camellia oil (80 %), almond oil (64-82 %), olive oil (55.0 — 83.0 %), avocado oil (59-75 %), peanut oil (66 %), sunflower oil (14.0—39.4 %), palm oil (35-45 %). 

In addition to oleic acid, water-based liquids also do an excellent job of sharpening and cleaning stones. One of the best is the Bori-Lube 10 liquid.

Bori-Lube 10 sharpening fluid is produced by one of the world's most famous manufacturers of abrasives, the American company Boride.  Designed to work with Boride synthetic stones, and diamond bars on any bond. The use of Bori-Lube reduces glares and is suitable for cleaning abrasives. It contains water and sodium tetraborate - an inorganic compound, the sodium salt of boric acid, the most common and often used boron compound. It is widely used for medical purposes as an antiseptic. 

Bori-Lube 10 allows you to sharpen stones made of aluminum oxide, such as the Boride T2 series, and also very effectively cleans the stones from the sludge after sharpening.