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Undercutting Slurry – Pictures, anyone?

Tok

Well-Known Member
Hello,

I´m very interested, what "undercutting slurry" exactly means. I still don´t get the point. I´d be very interested to see pictures of it, if that´s possible. This might be a great help for other Newbies, I guess.

Kind Regards,
Tok
 

BlueDun

Well-Known Member
Ok buddy, here's a quick try:

Click the picture.

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You will see that on some parts of the blade the slurry covers the edge and there are some "clody" slurry puddles further up the blade. As you pull the plade over the hone, undercuting means that you scoop up the slurry and it flows up the blade towards the spine.
On the right side there is no undercutting. The blade just glides over the hone but the slurry stays below the edge as it passes.

Cheers
BlueDun
 

Bart

Well-Known Member
Thank you Rico. :thumbup: I edited your post so it shows the picture at full size. I hope you don't mind.

I think that is a perfect illustration of undercutting slurry. We should include it in one of the articles of the sharpening academy. Any suggestions where it would be most "in place".

Kind regards,
Bart.
 

danjared

Well-Known Member
How about under "Fluid Behavior" in the Advanced Feedback Markers article? That seems like the best fit to me.
 

chti_lolo

Well-Known Member
Very interesting pic, Rico:thumbup:

I will be also interested by a picture showing the fluid behaviour (if available) in the finishing stage with water only.


Regards


Laurent
 

tat2Ralfy

Well-Known Member
Wonderful explanation and great picture :thumbup:

the effect is just the same when using water only

Best regards
Ralfson (Dr)
 

Paul

Well-Known Member
tat2Ralfy said:
Wonderful explanation and great picture :thumbup:

the effect is just the same when using water only

Best regards
Ralfson (Dr)

I start to get excited when I see the blade undercutting water :sleep:
 

chti_lolo

Well-Known Member
But what about the other side of the blade, is it something like a negative ?

tat2Ralfy said:
the effect is just the same when using water only
I thought that running up water was also a good marker, is it necessary to undercut the water?


Laurent
 

tat2Ralfy

Well-Known Member
undercutting water means it will run up the blade, thats exactly what we looking for both with the slurry and water stages

Best wishes
Ralfson (Dr)
 

chti_lolo

Well-Known Member
Sorry, this may due to my poor english:blush:
I thought that "run up" was more a kind of accumulation in front of the edge


Laurent
 

Paul

Well-Known Member
chti_lolo said:
Sorry, this may due to my poor english:blush:
I thought that "run up" was more a kind of accumulation in front of the edge


Laurent

Well, you want the water to be pushed along the entire edge, but as it gets closer to finished, it will run onto the blade.
 

shaved

Active Member
Just my 2 cent:

It's a good indicator for bevel and stroke but just like the hht it requires interepretation imho.

Slurry breaks the surface tension making it easier to get a false positive.

Moving the blade faster also helps to get water on it.

The water will also flow easier up once the upper side of the bevel is wet.

Using the blade at an angle will allow the water to flow easier from one side to the other.

Rasing one side of the stone when holding it does the same thing.
 

BlueDun

Well-Known Member
shaved said:
Just my 2 cent:

It's a good indicator for bevel and stroke but just like the hht it requires interepretation imho.

Slurry breaks the surface tension making it easier to get a false positive.

Moving the blade faster also helps to get water on it.

The water will also flow easier up once the upper side of the bevel is wet.

Using the blade at an angle will allow the water to flow easier from one side to the other.

Rasing one side of the stone when holding it does the same thing.

shaved, I will agree with everything you say.
However, the undercutting really is helpful, beacause if the razor does not undercut, you can be damn sure that you're not even close to a positive HHT ;)
But serious, I use it during the dilution phase every other dilution step or so. It will tell me quite reliably if I went too fast on the dilution or not. If so, I'll throw in another couple x-strokes until I'm there and then move on with the next dilution step.

Cheers
BlueDun
 

Bart

Well-Known Member
Indeed, these are excellent observations.:thumbup: I rely on watching what the fluid does a lot when sharpening razors.
 

Bart

Well-Known Member
The idea is that a keen edge will cut between the fluid and the surface of the hone. The thiner the coat of fluid, the more difficult this is for the edge. Only very keen edges can cut under a thin coat of fluid. Less keen edges, will run over the fluid, or they will need a thicker coat of fluid.

With proper experience, these kind of observations can tell you something about the keenness level of the edge.

You can also observe the contact point between the edge and the fluid in front of it, as guidance for your honing stroke. A good honing stroke first pushes the fluid in front of the heel, then in front of the middle part, and near the end of the stroke in front of the tip. That's a good stroke.

Kind regards,
Bart.
 

BlueDun

Well-Known Member
Bart, I would actually put the picture in the "Advanced Feedback Markers" section, right in the fluid behaviour chapter.
 
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