- 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.
- What is the difference between the RockStar series and the KUROMAKU series?
The RockStar series comprises solid 10 mm sharpening stones, available as either standard models (with no case) or together with a stainless-steel storage case.
The KUROMAKU series comprises solid 15 mm sharpening stones, which come with a plastic storage case. Both series are available in ten different grit sizes, but the lineup differs.
- What is the difference between the RockStar series and the GlassStone series?
The RockStar series comprises 10mm solid sharpening stones of a high quality equivalent to those in the GlassStone series.
The GlassStone series products feature 5 mm tempered glass laminated to 5 mm sharpening stones.*
The RockStar series has 10 different models, while the GlassStone series has a total of 17 types.
*Product no. 50106 features 5 mm tempered glass laminated to a 10 mm sharpening stone.
- What do the markings on the side of RockStar products stand for?
The type of stone, the country of manufacture and the lot number.
- What does 'class' refer to?
It indicates the approximate median particle diameter (size) of the abrasive material in the product, in micrometres.
When expressed in words rather than numerically, 'COARSE' represents the largest median particle size class, and 'NANO' the smallest.
- What does 'type' refer to?
It indicates the type of abrasive contained in the sharpening stone.
HA: Mono-crystalline fused alumina
PA: Pink alumina
WA: White alumina
A: Regular (brown) alumina
CA: Calcined alumina
HPA: High purity alumina
- Which face of the KUROMAKU series sharpening stones should I use?
You can use either face, but we recommend that you start on the side where no letters have been printed.
- 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 are sharpening stones made of?
Sharpening stones are made of abrasives such as alumina and silicon carbide, combined with binders and other compound materials.
- 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 of 40 micro and above (320 or below), then sharpen it using a succession of stones, moving from coarse to fine.
- Why do I still see scratches on the blade even though I have sharpened it with a KUROMAKU fine stone?
If you polish it with a finishing stone after sharpening it with a medium stone, but there is still slurry adhering to the blade or your hands, the blade may be scratched by the rough abrasive agent of the medium stone. Because of this, when changing whetstone and moving to progressively finer sharpening steps, it is important to wash off any dirt produced in the previous step. It is not enough merely to rinse the blade and your hands: you should carefully and thoroughly wash off any films of dirt on your hands, fingernails, and the surface of the blade.
- 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 of 40 micro and above (320 or below) used for?
Coarse stones are designed for adding an edge or removing large nicks on an existing edge.
- 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.
- Should the Lapping Disc be immersed in water before use?
There is no need to immerse it in water in advance, but do wet it when using it.
- Which of the surfaces on the Lapping Disc should I use, the flat one or the one with grooves?
You can use either surface - the grooved surface will give a slightly finer result.
- How do I use the Lapping Disc to perform 'dressing'?
First wet the entire surface of the sharpening stone. Next, take the Lapping Disc in one hand, and dress the entire stone surface by making small circular motions, but without applying too much force. There is no need to dress it for a long time: only one layer of 'skin' needs to be removed for the sharpening stone to regain its original performance.
- Do I need to keep water running constantly while sharpening a blade?
There is no need for a steady stream of water - you can sharpen your blades with just a splash of water on the stone surface. However, if you do let the water stream constantly, it means your hands stay clean while sharpening.
- Does a build up of slurry create any problems when sharpening?
It is fine to sharpen blades without washing away the slurry, but as Shapton sharpening stones have a high abrasive content, they can be used equally well with no slurry present.
- The GlassStone series includes two types each of the 4000, 6000 and 8000 sharpening stones. What are the differences between them?
They use different abrasive agents. GlassStone series 50603, 50703 and 50803 are recommended for sharpening composite steel blades, where steel has been forge welded with another metal.
- Are any of the KUROMAKU sharpening stones recommended for normal household knives?
We recommend the Orange Medium (1000) sharpening stone and Wine Fine (5000) finishing stone. If you intend to use only one stone, we recommend the Blue Medium (1500) sharpening stone.
- My sharpening stone no longer sharpens as it did when first bought - it slips and slides. What should I do?
It may have become clogged. We recommend that you try using a lapping plate.
- When I use "KUROMAKU Purple" for sharpening, it feels wrong.
"KUROMAKU Purple" is designed to give an optimum, unprecedented cutting feel to the blade tip (around 1 mm), so it may feel strange if used with conventional sharpening methods.
- I want to try using "KUROMAKU Purple", but the 'Precautions' state it should be used after "KUROMAKU Melon" － would it be OK to use it for sharpening after "KUROMAKU Yellow" instead, as this is finer?
That would be fine with high hardness steel, but for blades made from softer materials, please do use "KUROMAKU Melon". This is due to the stones' physical characteristics.