I've been a fairly long time user of ceramic Shapton whetstones these past number of years. I use a variety of brands of different stones, including a couple of natural stones, but Shapton has featured at some position in my whetstone line up more often than not. These stones have been produced in a series of iterations, with gradual refinements at each juncture, culminating in the 'Pro Series' and the most recent, the GlassStone Series. I've had the chance to try pretty much every stone the company has produced, and their dedication to research and producing a good product is most admirable. Besides the sharpening stones themselves, Shapton also sells an integrated, 'systems' approach, proving a float-glass backed diamond sharpening plate, or GDLP, claimed to be 'optically' flat, a rubberized block for holding the stones while sharpening, and a molded rubber tray to put the stone holder in, etc.. Heck I'm sure they even have a line of colorful Shapton condoms -- just a guess.
Having worn out the DMT coarse/extra coarse plates at a rapid rate (less than a year of use is all I could get out of them before they would delaminate) and finding them not especially flat, I was keen to try the Shapton GDLP, which has a claimed flatness of +/- 5 microns, easily 10 times flatter than the DMT. It oughta be flat, considering it costs in the neighborhood of $250! I faithfully followed manufacturer's instructions in the care of the GDLP, and never flattened stones coarser than #1000 on it. Over time I found it to be pretty good, better than the DMT at least, and it lasted somewhat longer, however it too has now begun to come apart:
A little closer in and it is more obvious - the black areas are bereft of diamonds:
It still sorta works and I am able to flatten stones with it if I'm careful, however I need something new, and for the price, I don't think I'll be opting for the Shapton product again. I'm considering going back to granite surface plate and wet/dry sandpaper, which despite it's messiness is relatively cheap and very flat.
Then there are the stones themselves. Now, sharpening is a somewhat idiosyncratic process, and variables in pressure, type of steel being worked, water, etc., all have an affect. There are stones that other carpenters love which I detest and vice versa. So, any comments I make about the 研ぎ味, togi-aji, or sharpening taste, as the Japanese refer to it, must be taken with a grain of salt. in fact, I'll largely leave that matter to one side. I tend to prefer harder slippery stones as opposed to gummy sticky stones, if that makes any sense to you. I don't use a sharpening jig of any kind, and tend to work the blade sideways-on to 45˚ or so in relation to the long axis of the stone.
I have several of the Shapton Pro Series stones, and of the set, I like the #2000 and #5000 the best. I don't care much for the stones coarser than the #2000. When the GlassStone series came out, I was intrigued, and I happened to be in direct contact with the US distributor at the time and he sung the praises of the new stones and sharpening system. I bought into that, literally, coming away with the #4000, #8000, and #16,000 stones. While the #30,000 of course had its attractions, the price was a bit steep so I held off. As the grit becomes finer, the price goes up, and not linearly but exponentially.
The curious thing about these stones are how thin the sharpening substrate is - a mere 5mm of abrasive on top of a piece of float glass which is itself 5mm thick. I understood at the time that there were plans to produce the stones with a 1cm thick abrasive layer, but I don't know if that has ever come to pass. A 10 mm thick stone (substrate + glass), for those of you who are metrically-challenged, is a little less than 7/16" thick. The Pro Stone Series are 15 mm thick, a hair more than about 9/16" thick.
The thinness of the stones was a bit of a concern, however there is marketing hype to allay such fears, and here I quote directly from the Shapton site:
"They may appear thin at first glance but, don't let that fool you. They will out last most other stones that are three times the thickness. These abrasives are extremely uniform. Consistency is the primary goal for Shapton's engineers. The abrasive that you encounter with the first pass will be the same on the 5,000th pass. And, this will be true for every every abrasive size."
Well, my experience with ceramic stones in general, and not just Shapton's stones, is that they are much longer wearing than other types of man-made whetstones. Given the unavailability of a thicker option a the time of purchase, and the reality of the price structure which would have meant that the thicker stones would be even more expensive, I decided to give the thin stones a try. After all, it did make sense as well that when a conventional stone gets thin, under 1/8" (3mm) in thickness, they are prone to breaking. With the glass backing on the stones, the promise was there to be able to use the abrasive right down to the last tenth of a millimeter.
Ah, well, there you have it, promises, promises. And there's 'Hope' - that sells oftentimes, like a good brand should, especially when the old brand starts to leave a stale taste in your mouth. My experience with these stones some 18 months on now has demonstrated that the life expectancy isn't quite all it's made out to be. The GlassStones have about the same durability as the Pro Series, that is they wear slowly, however I have not found they really serve you right down to the glass. After 18 months, my #8000 has lost about half the original thickness:
Ah, but that's not the real story. Here's how my three GlassStones look now - this is the #8000:
The #16,000 is worse:
And the #4000 has now started to delaminate and is junk:
The cracking an crazing began a few months back and has gotten much worse lately. It seems to get worse as the stone abrasive thins down to that last 2mm.
I did like the #4000 quite a bit, however it is now garbage. Unlike a conventional sharpening stone that becomes too thin to use, and breaks into pieces which can be re-cycled for use as little sharpening slips (for various smaller tools), the GlassStone is not recyclable really - it is just crumbling into little bits.
I suspect the #16,000 will give me another few weeks of service and the #8000, which I like quite a lot, will hopefully last another couple of months. However, I don't really feel they live up to their advertising, like so many products these days. How did Dubya put it?: "fool me once, shame on you, fool me twice....won't get fooled again". Yeah...
I am a bit curious about the newer series of gray-colored GlassStones, and how they might cut, but I think I will be looking elsewhere for the next set of stones and the next diamond plate or other stone-flattening system. For now, I have brought my old Pro series #5000 back into use to replace the #4000, and am looking around at options in regards to other finishing stones, natural and man-made.
I've had a good dance with Lady Shapton until she got a little wobbly on her feet, but I think I'll sit the next round out despite the fine new dress she's wearing. YMMV.