FAQ

The stones

Do Shapton stones need to be soaked in water before use?

No, Shapton stones do not need to be soaked except the very first time after purchase. We do recommend that on first use, you pre-soak the stone in water for five to six minutes to secure even smoother sharpening.

Do sharpening stones have 'best before' dates?

No, there are no time limits on when sharpening stones can be used.

What are the features of Shapton stones?

Shapton stones' characteristics include "High abrasive & sharpening capabilities", "Ready to use immediately" , "Reduced wear", "Long lasting" and "No smell".

What are the features of GlassStones?

The conventional image is that sharpening stones are large and heavy, but GlassStones are not only thin and light, but also strong, as layers of tempered glass are stuck together. GlassStones therefore have strong resistance to cracking or sudden breakage caused by external shocks such as being dropped.

I found some uneven colour on the surface of the stone I just bought. Is anything wrong?

No. It is in the nature of sharpening stones that spots or uneven colours appear on the stone surface. This is not a quality problem, and you can use the stone without concern.

Which surface of KUROMAKU should be used? Is there a front and back side?

Both surfaces of KUROMAKU can be used, but the first time, we recommend you start with the side without any printed letters.

Some white marble-like patterns have appeared on the sharpening stone's surface. Is anything wrong?

No. These white marbled patterns can appear on the surface of a sharpening stone under certain conditions, depending on how the stone is stored. This is not a quality problem, and you can use the stone without concern.

Are there any blade materials that cannot be sharpened?

All blade materials can be sharpened except ceramics and superalloys.

The plastic case that came with the unit has broken. Can I buy a replacement?

Yes. KUROMAKU cases can be bought separately from the main product.

What does "micron class" mean?

Micron class represents the coarseness, in another word, the size of the abrasive grains in a sharpening stone. The higher the number, the larger the grain size, in other words, the coarser the sharpening stone.

What does "type" mean?

Type represents the type of abrasive contained in the stone.

What are sharpening stones made of?

Sharpening stones are made of abrasives such as alumina and silicon carbide, combined with binders and other compound materials.

Is it OK to soak your sharpening stones in water for long time?

No. Don't soak our stones for more than 30 minutes, because this may cause the stone to become softer.

Is it OK to use hot water when sharpening?

No. Don't use hot water with our sharpening stones, because the water will cause extreme changes in temperature that can cause cracks.

Is it OK to use detergent with sharpening stones?

No. Don't use detergents with our sharpening stones, because they can cause changes in the quality of the stones.

How does one remove burrs?

Place the burred side of the blade against the sharpening stone, then remove the burrs by gently sliding it along, without much pressure.

Is it possible to sharpen a kitchen knife with a nicked edge?

If the nick is large, remove it using a coarse stone (25 micron class or coarser), then sharpen it using a succession of stones, moving from coarse to fine.

Sharpening with the 0 micron class stone feels wrong: what's up?

The 0 micron class stone is designed to provide a cutting edge with unprecedented cutting ability, approximately 1 mm wide. It may therefore feel strange if used to sharpen blades in the conventional way.

After sharpening a blade with fine stones (3 micron class or less), I noticed some scratches. Is something wrong?

If you sharpen a blade with a fine sharpening stone while your hands or the blade are still soiled with slurry from a previous coarse stone, the coarse abrasives can scratch the blade. It is important to wash off all contamination from previous processes.

Should sharpening stones be used in a particular order?

The usual order is to start with coarser stones having larger abrasive grains, then move to finer stones with smaller grains.

How often should blades be sharpened?

That depends on the blade's material, purpose and frequency of use, as well as the level of cut you are seeking.
Our recommendation is to sharpen a blade whenever you feel its cutting ability has declined.

What are coarse stones (53 micron and above) used for?

Coarse stones are designed for adding an edge or removing large nicks on an existing edge.

What does "Tomozuri" mean?

Tomozuri means to rub the surfaces of two stones or plates against each other.

Do Shapton stones come with a Nagura Stone?

No. Shapton stones do not need a Nagura Stone, and lapping with a Nagura Stone will leave the surface rough and ragged.

Is it OK to use oils with your sharpening stones?

Yes, it's fine to use oil with the stones. However, once you've used oil on a stone, you should always use oil with that stone.

Recent KUROMAKU stones look different from the designs bought in the past. Is there any difference in spec?

No. The only change was in the printing design, not in the quality or specs of the stones.

M5 Series

Each stone in the M5 Series measures 210 x 70 mm with a 5 mm abrasive layer. They come with an easy-to-carry storage case also usable as a stone holder while sharpening.

S1601 M5 White, Coarse (120)
S1606 M5 Moss, Coarse (180)
S1607 M5 Blue, Medium Coarse (1000)
S1603 M5 Green, Medium Fine (2000)
S1604 M5 Wine, Fine (5000)
S1605 M5 Cream, Extra Fine (12000)

* M5 Series products are sold only in Japan.

M15 Series

Each stone in the M15 Series measures 210 x 70 mm with a 15 mm sharpening stone attached to a wooden base.

0706 M15 Moss, Coarse (220)
0702 M15 Orange, Medium Coarse (1000)
0707 M15 Blue, Medium (1500)
0703 M15 Green, Medium Fine (2000)
0704 M15 Wine, Fine (5000)
0705 M15 Cream, Extra Fine (12000)

* M15 Series products are sold only in Japan.

M24 Series

Each stone in the M24 Series measures 210 x 70 mm with a 24 mm sharpening stone attached to a wooden base.

0801 M24 White, Coarse (120)
0802 M24 Orange, Medium Coarse (1000)
0807 M24 Blue, Medium (1500)
0803 M24 Green, Medium Fine (2000)
0804 M24 Wine, Fine (5000)

* M24 Series products are sold only in Japan.

Lr250 Series

Each stone in the Lr250 Series measures 250 x 100 mm and is attached to a wooden base.

0901 Lr250 White, Coarse (120)
0902 Lr250 Orange, Medium Coarse (1000)
0903 Lr250 Green, Medium Fine (2000)
0904 Lr250 Wine, Fine (5000)
0905 Lr250 Cream, Extra Fine (12000)

* The different types have different thicknesses.
White / Orange: 20 mm
Green: 18 mm
Wine / Cream: 15 mm

* Lr250 Series products are sold only in Japan.

CABADO Series

Each stone in the CABADO Series measures 250 x 100 mm with a 20 mm sharpening stone attached to a wooden base.
The stones are sold in sets with dedicated stone holders. The wooden base stuck to the back of each stone is provided with an opening to fix it to the stone holder.

0301 [Discontinued] CABADO, White, Coarse (120)
0302 [Discontinued] CABADO, Orange, Medium Coarse (1000)
0303 [Discontinued] CABADO, Green, Medium Fine (2000)
0304 [Discontinued] CABADO, Wine, Fine (5000)
0305 [Discontinued] CABADO, Cream, Extra Fine (12000)

0401 CABADO, Replacement, White, Coarse (120)
0402 CABADO, Replacement, Orange, Medium Coarse (1000)
0403 CABADO, Replacement, Green, Medium Fine (2000)
0404 CABADO, Replacement, Wine, Fine (5000)
0405 CABADO, Replacement, Extra Fine (12000)

* Currently the only CABADO Series items in production are replacement stones, and these are sold only in Japan.

The lapping plates

What is the difference between KUBO and NAORU?

KUBO is made of cast bronze, with diamonds electrodeposited on its lapping surfaces. It has a front side for lapping sharpening stones, and a back surface for fixing damaged blades.
NAORU is made of gray cast iron, and comes with lapping powders to be sprinkled on its surface before use.

When flattening some fine stones (2 micron class and below) with a lapping plate, the finish obtained on the sharpening stone surface is not the same as when they were first bought. Is anything wrong?

This type of stone should be soaked in water for about 10 minutes before applying the lapping plate.

Can NAORU be used to flatten natural sharpening stones?

Yes, NAORU can be used to flatten natural stones too.

The lapping powders that came with NAORU have run out. Can I buy replacements?

Yes, the powders are available separately.

Is there a way to check whether flattening has been done correctly?

As a guide, use a pencil to draw a grid on the stone surface to be flattened.
Parts where the lines get erased show where the lapping plate has made contact, i.e. where flattening has been performed correctly.

How many times can a Diamond Glass Lapping Plate be used?

A Diamond Glass Lapping Plate is usually good for around 1,000 to 3,000 applications.

Can a Diamond Glass Lapping Plate be used to flatten sharpening stones of any grit?

The DGLP is suitable for flattening fine stones, of the 25 micron class or under.

What should I do if my KUBO's sharpening ability declines?

Diamonds do get worn out over time. If the KUBO's performance has declined, we offer a diamond re-electrodeposition service.

I flattened some fine sharpening stones (2 micron class or below) with a brand new KUBO, but the finished surface was rough, not smooth like a mirror. What can I do?

A brand new KUBO has diamond projections from the surface. Before using it in this way, use the KUBO to flatten some sharpening stones of the 6 to 25 micron class several times.

I flattened a sharpening stone with NAORU and fine lapping powder, but the finished surface was rough, not smooth like a mirror. What can I do?

Use some medium lapping powder and remove the softened parts, then thoroughly wash off any dirt, before finishing the surface with some fine lapping powder.

Where can I apply for the KUBO Re-electrodeposition Service?

For KUBO Re-electrodeposition you can either call a Shapton dealer or Shapton directly.

A fine stone (3 micron class or below) seems to have lost some sharpening ability since I flattened its surface. What might be wrong?

When flattening fine stones of the 3 micron class or below, please use a lapping plate such as KUBO, DGLP or NAORU with fine lapping powder.

My NAORU seems to have lost the ability to flatten sharpening stones. What should I do?

We can correct NAORU flatness.
To make use of this service, please call a Shapton dealer or Shapton directly.

Can I use KUBO to flatten sharpening stones of any grit?

No. KUBO can only be used for flattening fine stones below the 25 micron class.

Can I use Shapton lapping plates such as KUBO, DGLP and NAORU to flatten diamond sharpening stones?

No. These lapping plates are not recommended for use with diamond electrodeposited sharpening stones because the surfaces can be damaged.

Maintenance

I feel a stone's sharpening ability has declined since I bought it. What might be wrong?

One possible cause is deformation of the surface. We recommend you flatten it, to keep the sharpening surface in prime condition.

What should I do if a crack opens up on a sharpening stone?

Cracks can form when a sharpening stone is not used for some time, or if usage precautions are not observed. The main causes are sudden drying or extreme changes in temperature.
Shave off the surface at the cracked part. Cracks get deeper as they get wider, so it is important to do this at an early stage, while the crack is still small. If the stone is used in an extremely dry environment, we recommend keeping it in a plastic bag or a sealed plastic container, to prevent acute dry-out after use.

What should I do if a sharpening stone gets clogged?

We recommend using our Lapping Disc, a dressing stone.

How should I take care of my stones after use?

After using a stone, wash any dirt off with a sponge or similar. If dirt is left adhering to a stone, its sharpening ability can decline.

What's the best way to store stones?

Don't leave stones outside or expose them to direct sunlight - both can cause weathering and cracks.

Is it OK to use sandpaper to flatten a sharpening stone's surface?

No, abrasive paper can leave a stone clogged, with the result that the blade slips and it is impossible to sharpen it.

What should I do if the surface is no longer flat?

Sharpening stones start deforming the moment they are used to sharpen a blade. Repeated sharpening then causes the flatness of the blade to be damaged too, mirroring the deformed surface of the stone.
Use a lapping plate such as KUBO, DGLP or NAORU to return the surface of the sharpening stone to its flat state.

Is it possible to flatten stones by lapping them on each other?

Lapping stones against each other can be OK but is not recommended. It is better to use a lapping plate, which enables more accurate flattening.

Is there anything I can do if a fine stone (3 micron class or below) has become soft?

It is likely that storage conditions caused the stone to soften and its quality to change. In such cases, shave off the softened parts with medium lapping powder, wash off any dirt completely, then finish the stone surface again using fine lapping powder.

Is it OK to use your Lapping Disc to dress a sharpening stone of the 20 micron class?

Yes. The Lapping Disc is designed for dressing sharpening stones coarser than the 8 micron class.

Miscellaneous

How much do Shapton products cost?

We do not specify the retail price of Shapton products: please ask your Shapton dealer for their current price list.

Can Shapton stones be used outside Japan?

Yes, Shapton stones can be used anywhere. However, please note that particularly dry areas can cause the stones to crack.