Silicon carbide kasumi diy

[refcast]

I was asked by ethompson to explain the sic powder kasumi so here's a DIY demo guide. Be careful of course.... It's very easy to slice myself doing this and I have a lot of cuts from it. Always wear gloves.

Needed
1. 220 grit sic (silicon carbide)
2. 220 grit 3m sandpaper
3. 5mm creatology foam cut to about 1.5 in x 1 in
4. Oil of choice. I used almond oil
5. Disposable gloves
6. Paper towels
7. Foil to catch spilled oil

Process
1. Put on gloves and put foil over work area
2. Tear out sandpaper in a 1.5 x 1inch rectangle
3 Cut out foam about the same size. Big enough to fit under the thumb comfortably
4. Apply oil to blade. About a teaspoon
5. Add sic powder onto oil
6. Mix and distribute over blade
7. Put sandpaper face down on blade on oil/sic mixture
8. Put foam down and press so that it sticks. Push down for a bit to remove any oil that might get trapped between foam and sandpaper. Sometimes adding a little paper towel between them helps. And or Sic powder as well.
9. Rub the foam pad/sandpaper "fingerstone" on the blade. When the sandpaper is worn through, get a new piece of sandpaper. When the Sic feels like it dulls, wipe the blade clean. Check your progress. Add more Sic and oil and repeat.

FAQ
1. What grit can I sand from?
Answer: I started from 400 grit and it took me an hour or two total to remove most of the scratches. 400 grit is doable but make sure all the scratches are as shallow as possible on the stone before moving to the sic kasumi, so save time. I'd also recommend sharpening the core steel to 1000 grit or 3000, since the steel is slower to abrade, and it's harder to sand the edge without dulling it or cutting yourself.

2. How do I hold the blade while sanding?
Answer: I'm right handed and I hold the blade with my left hand and sand with my right. I sand about 2-3 inches, which give me more control and reduces the chance of cutting myself. If I'm sanding near the edge I only sand away from myself in one long motion with less pressure.

3. I'm chipping the edge or dulling it, how to I prevent that?
This is inevitable but you can take precautions against it. Use less pressure near the edge. Wherever you see the grit move, there's abrasion. Use a higher grit sandpaper, 320 is less likely and less able to catch on the edge. Have the sandpaper overhang less over the edge. Have the foam directly over the sandpaper.

4. Does this work on honyaki?
Yes it does, see my honyaki gyuto sale post where I painfully tried to do this over and over.

5. How long does it take?
It took me 6 small pieces of sandpaper for each side and about 2 hours total from a 400 grit stone. The sic and sandpaper method is very abrasive and about as fast as a 1.5k-2k stone. Geometry will smooth and flatten as sanding continues

6. What grit finish does it leave?
It's about a 3k finish but it's very shallow.

7. Is there a difference based on how much pressure I use or time I sand?
Yep. Lighter pressure makes lighter scratches and more sandblast finish. The grit breaks down over time and sandpaper dulls so the finish gets finer

8. What are those little grainy things on the iron or steel?
That's alloy banding. The sic method can show them subtly but surely on iron and steel.

9. How can I finish finer?
Use oil and loose 220 sic powder and gloved hands to move the grit around. Aluminium foil can work too over the foam, but I haven't tested it. This can get pretty close to a mirror. Then 1000 grit aluminum oxide and oil can get to a bright clean mirror. See my honyaki gyuto sale post for an example of this finish. No metal polish or diamond paste needed. Finer finishes stick more and are less grippy for pinch grip

10. How is this better than sandpaper?
The scratches are more uniform by far, and it's faster. Powered sanding is faster though.

11. Deep cracks are appearing on the steel, what's wrong?
Congrats, it means your working on honyaki lol. If you use SiC or AlOx and oil applied by gloves on honyaki, cracks can appear. These are just super deeper scratches that get opened up more and more by each pass of the abrasive. The scratch is abraded preferentially so it gets wider, so that's what it is. To avoid. . . Idk hahaha. I forgot I how I solved that one.

12. Can I do this on ura?
Yes, sure can

13. I'm polishing hard steel and some spots turn darker. What's going on?
It means that those spots didn't harden during the quench.

Result

 

[dehory]

What do you think about Micromesh vs the foam and sandpaper combo?

 

[refcast]

@dehory I had micromesh a while back but I always seemed to just use it up. Either it clogged or dulled I'm not sure but sandpaper seemed to work better for me and I havent tried micromesh in years

 

[Choppin]

@refcast only saw this post now - very interesting and knife looks great.

the finish looks finer than I'd expect given the 400 grit... is this because the abrasives in the SiC and the sandpaper abrade each other, thus getting finer than only using sandpaper?

this seems specially useful when removing scratches from thinning / coarse stones... it's always the longest step for me in a polishing progression. I'll try adding SiC next time to speed things up.

 

[refcast]

@Choppin the abrasive grains in the sic aren't pressed very hard into the blade with foam and sandpaper. When I used a thin brass backing instead of sandpaper and pressed harder, then I would see deeper scratches.

 

[KenjiF]

Wow, that looks awesome! Thanks for the post

 

[knspiracy]

Why the gloves? Many bench stones are SIC based... gloves not needed?

 

[tostadas]

Gloves are always nice to keep your hands clean.

 

[refcast]

XD.

I used no gloves before too. Then I sliced myself over and over again. Gloves helped to greatly reduce that, even if they were just black nitrile gloves. I apply the sic to the core steel too, so I do go right next to the edge.

Moreso, when I want a finer kasumi or polish, I apply the sic with oil, but no sandpaper. So I rub it on the blade, with gloves. With no gloves I tried, but I abraded off my finger pads and they started bleeding

 

[Logan A.]

This is great! I’m going to give it a try. Could you link some pics of the honyaki that you did?

 

[refcast]

https://www.kitchenknifeforums.com/threads/240mm-honyaki-gyuto.56656/
@Logan A.

 

[refcast]

It's also possible to use soapy water instead, but moisture management is more sensitive. I dip my finger into the sic powder and add it to the blade as I work on it to adjust the water:sic powder ratio, until I feel it cutting fast enough

I used water instead of oil for this project

https://www.kitchenknifeforums.com/threads/210mm-heavy-tapered-chef.70039/

 

[SammieM]

@refcast
Great job mate!
Say do you have to prep the knife the way you’d prep it for finger stones?
Also, is the foam you use similar to EVA or is it softer?
Thank you!

 

[refcast]

@SammieM

Prep -- not too bad, of course more is better. It can get out some 400 grit scratches. Slower on steel so polish it more or so more prep on it vs iron

Foam is a sense closed cell foam -- has some give but doesn't completely collapse. Helps it go around curves and inconsistencies

 

[SammieM]

@SammieM

Prep -- not too bad, of course more is better. It can get out some 400 grit scratches. Slower on steel so polish it more or so more prep on it vs iron

Foam is a sense closed cell foam -- has some give but doesn't completely collapse. Helps it go around curves and inconsistencies

Thanks mate! I might give it a go in my Migaki Yoake…

 

[refcast]

Also danger! If you cut yourself while doing this you can give yourself a silicon carbide tattoo under your skin . . . Speaking from experience

 

[SammieM]

Also danger! If you cut yourself while doing this you can give yourself a silicon carbide tattoo under your skin . . . Speaking from experience

Thanks for warning me bud. I’ll wear some gloves and see how that goes. I have access to some high quality surgical gloves that fit better than the nitrile variety.. They are more difficult to cut as well…

 

[refcast]

Correctional to post #14
*dense close cell foam

When I press it down for refinishing it reduces in height by like 25% or so