I've thought about the under water technique. I used that on a needle hone that belonged to my grandfather honing a knife.

There is nothing objective about honing, a bit of pressure, no pressure, light slurry, dense slurry, fast and slow stones, there is no definition.

I have 7 citoticules i think, they all behave different, but they can all provide hht5+ edges on a proper knive. Some stones reach that with dilucot, for some i need to finish under a running tab. With charnley forrest, welsh slate, esher,... this feels overhoned but with jnat and coticule scary sharp remains soft.

But, scary sharp and soft is a dangerous combination. You can shave with any angle and some pressure without causing any irritation, but suddenly, no warning you cut yourself.
Hht3/4 shaves nicer, the beard is shaved just as efficient/ short, but with more soundfeedback, you dont need to make scything movements, but you can, you dont need pressure but you can use it,...

A few passes on Crox and certainly feox kill the unique softness of a coticule a bit, you cant press your thumb on the edge anymore without cutting yourself, but it remains a soft edge. After some stropping the edge changes anyway.

On crooked blades a pasted strop can be so much easier,...

But if you prefer cf or welsh slate after cotucule, go ahead, mixing stones, why not,... after 5 shaves and some stropping i have a hard time to guess what stones i used for honing, but the difference between a dovo kern juchten and japanese cordovan becomes more obvious,...

Thanks - this gives me a nice comparison I think.

When you reach hht5+ are you doing that with a single coticule all the way through? If you are finishing under water, is that after a dilucot progression?

The running water is part of the dilucot, in general with the same stone. I start on slurry, 20 strokes and a drop of water, 18 strokes,....... and after a while a drop after each stroke a start with a dripping tap and end with a ligth running tap. The endpoint is different for each stone. I have a stone where i prefer to finish on light slurry, and i have a stone that needs a dripping tap to get hht4, but that still reaches stupid scary sharp.
But i use stupid scary sharp for chissels, not for razors.

I use whatever stroke i think is needed,cirkles half strokes, x strokes, rocking, flat,..

I hardly use the cf and welsh slates, just enough to keep the feeling, eshers also rather seldom, jnat sometimes and the majority of the honing happens on coticule or the bbs back end of a coti,...

Please explain how running water is different from spraying water on the coticule? Thanks.

I have a Lovely French Barbers Finishing Coticule...I Use Running Tap Water...Holding the Stone in My Hand...I Dont Want Any Swarf or Slurry as its a Finisher...It Keeps the Stone Clean & the Blade Seems to Suck Down Better & I get a Better Feel...Thats Me Talkin Mind...I Reckon this Stone is around a 10 K + Finisher with Water...I Use Tallow Lather to Finish & Reckon it Pumps Out around a Good 12 K + Edge...

A Smooth Finishing Coticule is Not Easy to Find...French EBay is the Place where I see a Lot of Proper Barbers Coticules...This Particular Stone is as Consistent as a Synthetic for Me...I Will Pre Finish on a 12 K Naniwa Super Stone then Finish on My Coticule...

I Usually Use it for Thinner Ground Sheffields or Some Thinner Ground Carbon Solingen Blades...In Sum..I Am Lucky..I Have a Good Un..And its a Keeper for Sure & the Song I Got it for...Many are Way Over Priced & Not Fit for Finishing SRS...I Love Using it..

Billy..

Thanks Billy.

As ever great information and reference points. I think I have one of those cotis from France, but so far best results have been from oil - like Tim describes further up. I will try it moving from a 12k.

The La Grise works well under water.

Tallow lather- is the tallow significant do you think? I've used regular lather and it makes the stone feel gritty.

Fully paid up hand held honer after advice from you and @Arnout last year. It transformed my honing - belated thanks for that.

My stones are so small, I have to hold them...LOL!!

I Use Vitos Tallow Soap...Similar to Cella...Its Oily & Fatty..I Use it on My Escher Thuri as Well..Funny Enough is Does Feel More Gritty But it Sure Picks the Edge Up with Very Light Strokes...For Me Anyway...Never Used Oil on My Coticule..Just Do what Works for Me...Oh..Forgot..I Add Glycerin to the Tallow Soap...The French Barber I Got it from Used the Same Method as Did his Father and Grand Father...I Spoke to Him on EBay about it..

Thats Me Talkin Mind..I Just Do what Works for Me & My Particular Stone & Delighted with the Results...I Only Use this Stone as a Finisher with a Superb Shave Ready 12 K Naniwa Super Stone Edge as My Pre Finisher So Ta Speak..

I Use the Coticule as a Post Natural Finisher if there is Such a Thing as I Use a Synthetic Progression...Just Made that One Up for Me...

Billy..

I am with ya @Billyfergie

I am a Coticule Finisher also, Chosera 1-5-10 and into the finish is the norm

Done the whole Grindercot and tried it out, just don't see it as any better, of course, I have a good finish Coti and not a good cutter so that could be the difference

Right... Hopefully I will get this right. I just checked the physics with an engineer. I am repeating what I was told, please no-one shoot me down if I get it mixed up

Generally you use water or oil to remove swarf as you hone, allowing the stone to abraid the metal evenly according to interaction of the surface with the metal.

Water has a surface tension that creates a kind of pillow that kind of gets in the way. The surface tension also creates a suction if the metal becomes smooth enough against the stone. Two matching surfaces will force any air out and the water acts like a seal. You can see this easily with a fine grit slip stone on a matching stone. Try raising a slurry from a Charnley Forest slip stone on a Charnley Forest. You get an extreme amount of suction.

The pillow effect is reduced if you break the surface tension. You can do this by diluting with soap or glycerin, or by increasing water flow.

If you hone under a dripping tap, when you reach the point where the two surfaces + the amount of water between them are starting to seal you feel resistance and suction. This indicates you have reached the point where the two surfaces are most matched given that tension of the water between. If you increase the flow from the tap (faucet) you break that level of surface tension, reduce the "pillow" and you get a closer contact between the steel and stone. It works like a grit progression but at very very fine levels. Progressive suction at lower and lower surface tension, polishes out the scratch pattern at finer and closer levels.

I think this generally works under running water because you need the water to be coming over the blade (like airflow over an aeroplane wing), although I think I have felt it with just a lot of surface water. The problem with just spraying is you don't break down the surface tension enough to get the finer polishing.