Thread: Scratches after lapping a Shapton 16k glass stone

Originally Posted by jeness

The 5k compared to this is like a piece of glass, silky smooth all the way, without any smoothing with higher grit stones.

I am just a bit surprised, because a lot of people are using their shaptons lapped with 325 DMTs and 400 Atomas, and they didn't have a problem like me.

The 12k should be smooth like your 5 k.
3 people on this page other than you have had similar problems so we're just all lucky.
If it's only in isolated spots you could just use the stone & wait until regular lapping removes the problem. My one was faulty only on one edge so I just turned it round. Eventually it smoothed out. You should mark your stone & set a limit on how much you are prepared to lap tho. Sometimes a product warrants returning.

I bought a 16k stone a month ago and have been pulling my hair out. 8k leaves a mirror-like shine and 16k leaves deep streaks like a 1500 grit stone would leave.

Then it dawned on me - I'll bet the Shapton 16k and 30k have periodic manufacturing issues simply because a supplier mistakes those 4 zeros for 3. So, in every few batches you might be getting a bunch of grit added to a batch of 16k stones that's 1600.

Knives & Stones in Australia kindly offered to refund the stone & shipping and will arrange to get this particular stone back to Shapton to find out.

I don't think you're losing your mind at all.

First of all, Shapton does not make a 1600.

Second, "every few batches?" Do you really think any company could function that way?

Did you lap the 16k? If so, with what?

What other GlassStones do you have?

interesting... I just acquired the 16k GS. I too noticed the scratches on it after lapping (DMT 325) but only under
a 40x loupe. I lapped it again but very softly for quite a while....20 mins or so and the scratches were still visible. I decided to just go ahead and use it anyway on a pretty average stainless blade I got on ebay. First I gave it the norton 4/8k treatment and then straight to 16k GS.... followed by a few back strokes on crox balsa then strop. 50 linen 50 leather. The result was the finest straight razor shave I've had yet. I'm well pleased with the 16k finish. It might be too early to say but it seems to me to be a sharper and smoother finish than the nani 12k. not selling the nani yet though. lots more experimenting to do.

On realynfine stines aspecialy sinthetic stines lappingnshouldbbe done onndiamond plates, preferably under running water to wash away the grit. You dont need tonprep the stone surface higher then 600 grit...just use a nagura or rubbing stone.

Higher grit is dangerous because it can remain embeded in the stone and it's harder to wash out.

Avoid using low quality sandpaper that drops grit like crazy when wet.

Getting a finer finish on the stone will not solve the problem...
Get it under running water...lap again with the lapping plate...then use a nagura tobrub and prep the surface under running water.

It may also be a problem in the stone that you accidentaly started to notice after lapping....but the change in performance is whatbworries me.

Scratches shouldn't hurt anything if it takes magnification to see, but you could check your plate and see if you have a few high crystals, I worked my DMT with a heavy cleaver to break it in. But if it ain't catching your blade t should be fine. After a while the DMT will wear down pretty smooth, makes for good slurry. Tc