Thread: My razor is too sharp???? I like a duller edge??

Originally Posted by Seraphim

That's a pretty smooth edge (Dovo Renaissance stainless). I used a hanging cavas strop.

That's pretty smooth if you're used to looking at 1 micron diamond. But it's pretty rough by 0.5 micron chrome oxide standards. Look at verhoeven's paper, page 27, figures 32 and 33. These were taken at 600x and 3,000x (with an inset detail at 10,000x) taken with a scanning electron microscope, and in the 600x shots the bevels look like a perfectly smooth plane. In the 3,000x shots the details look similar to yours - but at that point he's at six times your resolution. (If the angles look steep in these photos that's because they are. IIRC he's at honing at 48 degrees).

For comparison, here's a shot of an edge honed with 1 micron diamond, taken from pg 42, figure 48(b). 600x again.

Originally Posted by randydance062449

I agree with this. The diamond pastes leave the edge/bevel just to harsh for my skin. It feels like the 0.5 chrome ox smooths down the scratches left by the diamond pastes.

What type of diamond (spray?/paste? micron?) are you using Randy and what are you using it with? Leather? Cotton? Felt? I find significant differences in the types of diamond and media used where I could not say that they all produce harsh results.

Thanks,

Lynn

Good point about crystal shape, diamond vs the round shape of Chromium Oxide.

The points made above about purity are important. Paraphrasing, if the average particle size is 0.5 micron, but there are significant numbers of particles ranging up to 2 microns, then all bets are off! I asked Kremer Pigments about this very point. I am including their reply below.

Basically, they guarantee a high level of purity. So, if there are larger (or smaller) particles, there aren't many. But, they do acknowledge that larger particles exist, because if I understand correctly, residue is left after sieving.

My only other comment about the 0.3 micron Kremer Chromium Oxide is that EVERYONE who has used anything by Kremer believes that they produce very quality products, with a very high level of purity. After spending a long time with my microscope viewing a blade after 0.25 diamond, 0.5 chromium oxide and 0.3 chromium oxide, and lately 0.09 micron iron oxide, I have to agree that the Kremer products are quite pure.

Here's their letter...

Hello Larry,

Our chemist in Germany which answers very specific questions, Eva Eis, forwarded this email which she thought she previously sent you. I have attached it to the body of this email.


Dear Mr. Andreassen,

I am sorry, but we don´t have any data about largest and smallest
particles. It is difficult to measure these fine pigments and usually only
the predominant particle size is given. Agglomerates may be larger, as you
can read from the sieve residue of 0,02% in a 45µ-sieve. Purity of the
pigment is approx. 99%.

Best regards,
Eva Eis
Diplom-Restauratorin


We definitely recommend tests prior to the final application, we can not
guarantee for any instructions given.


--
Kremer Pigments Inc. NYC

Phone (212) 219-2394
Fax (212) 219-2395
1 (800) 995-5501

USA Store Location:

247 West 29th Street
New York, NY 10001
(Btw. 7th & 8th Aves.)
Open:
Monday - Saturday 11:00am - 6:30pm

Ultimately, magnification is not just about the lenses. You also have to factor in the camera resolution, as well as screen size and resolution for the viewer. I'm looking at this thread on a 15.4" laptop, someone else may be using a 26" monitor, the images are going to be different sizes depending on this and screen resolution, thus effective magnification is different.

Does yuzuha post here? She had this all explained a few years ago, but it's not something I know all that well.

Originally Posted by mparker762

That's pretty smooth if you're used to looking at 1 micron diamond. But it's pretty rough by 0.5 micron chrome oxide standards. Look at verhoeven's paper, page 27, figures 32 and 33. These were taken at 600x and 3,000x (with an inset detail at 10,000x) taken with a scanning electron microscope, and in the 600x shots the bevels look like a perfectly smooth plane. In the 3,000x shots the details look similar to yours - but at that point he's at six times your resolution. (If the angles look steep in these photos that's because they are. IIRC he's at honing at 48 degrees).

Honing at 48 degrees?

That' s a cakewalk compared to what staright users must contend with (as you well know).

Yeah, the depth of the sawtooth effect the abrasive will have on the edge is greatly increased as the angle is lowered, plus worrying about microchipping. Finish on the bevel sides should be pretty consistent, I would expect.

Originally Posted by Seraphim

Honing at 48 degrees?

That' s a cakewalk compared to what staright users must contend with (as you well know).

Yes, he mentions that in his paper.

pg 14

The effects of changing the 2β edge angle are illustrated by comparing the blade of Fig. 17 which had 2β = 70o to Fig. 16 where 2β = 50o. ... The larger angle produced noticeably more breakout along the edge, an effect which was confirmed to increase as the angle was increased over the 3 values studied, 50, 60 and 70o.

and pg 21

...however, sharpening a blade with the 2β edge angle of the razor blades, 17o, is more difficult than a blade with the 2β edge angle of 40o.

Which brings up an interesting question: why is the standard honing angle for straight razors is 17 degrees and not 20 or 30 or 40 like knives? FWIW both the Gillette blades he tested and the straight razor he tested had 17 degree honing angles.

The answer for straight razors may simply be the weight of such a heavy spine, or maybe the necessity for shaving with a lower angle and the wide spine would get in the way. But I'm not sure that either explanation is sufficient. Framebacks solve the weight issue (and given the popularity of the big 8/8 wedges clearly weight wasn't *that* much of a problem), and a 40 degree honing angle is only 20 degrees either side which doesn't seem unworkable given that 25-30 degrees is a common angle for shaving. So why 17 degrees? We've seen that going much lower than that makes for an edge that is simply too weak to hold up, so that explains why it isn't lower, but why isn't the standard angle much higher? And Gillette certainly didn't have to worry about weight or spine thickness, yet they went with the same angle. The Feather has a final bevel angle of 25 degrees, yet their primary bevel is I believe right around 17 degrees (I can't find Zowada's post where he gives the angles for the various bevels on the Feather, so if somebody runs across that post please feel free to correct me).

Originally Posted by hardheart

Yeah, the depth of the sawtooth effect the abrasive will have on the edge is greatly increased as the angle is lowered, plus worrying about microchipping. Finish on the bevel sides should be pretty consistent, I would expect.

Neither Verhoeven's photos nor the photos from other guy a few months ago that posted SEM photos of his own edges showed any evidence of sawteeth at 3000x. Verhoeven's photos show sawteeth from honing at coarser grits, but not once you get up to the sorts of abrasives that we use - once the depth of the scratch marks is lower than the edge width then they may as well be farm furrows running off the cliffs of Dover.

Can I vote this the greatest thread ever?

Originally Posted by mparker762

Which brings up an interesting question: why is the standard honing angle for straight razors is 17 degrees and not 20 or 30 or 40 like knives? FWIW both the Gillette blades he tested and the straight razor he tested had 17 degree honing angles.

Cutting - or better: chopping - a hair: is forcing a steel wedge in between the keratin cells of the hair. As we already discussed, the width of the tip is very important for penetrating the outer cells. But also the width of the steel that follows the very apex of the cutting bevel is important. The greater the bevel angle, the faster the bevel beefs up. That will have an effect on how easy the wedge cleaves the cells.

I believe, the smaller the bevel angle, the easier is will cut, but at a certain point, the long and thin bevel becomes too weak, so a compromise needs to be made.
I looks like that compromise centers around 17 degrees.

I also think that an edge with of 0.3 micron is much keener than an edge width of 0.4 micron. It might be a small difference to grasp, because we are not accustomed with dealing dimensions that small, but for severing organic structures, 0.3 is 25% keener than 0.4
I am adding this, because I think that having a keener edge width at the very tip can to some extent make up for having a bigger bevel angle.

Bart.