Escher water hones are known far and wide by straight razor shavers as being one of the, if not THE finest sharpening stone for straight razors. Just like a Belgian Coticule, these are natural stones, which come with a "slurry stone" or small hunk of hone (made of the same natural stone as the escher) to rub against the wet hone to create a milky, abrasive slurry. These stones can be used with - or without slurry. Basically this allows 2 modes - mode 1, with slurry, which will cut much faster and more aggressively, and mode 2, without slurry, which will cut slower and form a finer edge. While a Belgian Coticule is often around 8K grit, Eschers tend to be around 10-12K grit, so it provides a finer level of polish.
So where do you get an Escher? Well... that's sort of the problem, and to a large extent why there is such a cost associated with them. They are quite difficult to find, and depending on the grade of the stone (IE Blue-Green or Yellow-Green) they can be absurdly expensive... sometimes more than a custom, damascus straight razor. You can also often find new, or new old stock Thuringian water hones, which are essentially the same thing, yet at a much lower cost. Even these typically (for a decent size stone) are close to, or over $100, so by no means is this an inexpensive stone.
Overall these stones are quite nice, and like Belgian Coticules are a real hoot to use - but I just don't think they're worth the hefty price tag. Personally I feel a Chinese 12K or a Spyderco Ultra fine work every bit as good, and are significantly less expensive stones. If you are a "hone junkie" I certainly would suggest picking one up, but if you're merely looking for results, there better and less expensive options.
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