I have used thin oil (baby oil) in the past, and while it worked very well for smoothing the action and flushing the old swarf away, the smell is unbearable. I find perfumy smells completely repulsive, but thankfully you can buy unscented baby oil in most towns, just not here. I used mineral oil thinned with unscented (haha!) mineral spirits. It works just fine and also seems to prolong the life of the sandpaper that I was using, much better than water. Interesting... Is the oil actually lubricating the abrasive grains and reducing the amount of shear forces being applied, reducing fracture? Is the water having a mild solvative effect on the abrasive itself or perhaps the reducing the adhesive bond? It FEELS like the oil had a greater cushioning effect, even when thinned to water consistency. I don't know if one works better than the other.
What I DO know is that oil is messy. VERY messy and and somehow spreads black nastiness everywhere. I also have a peculiar autonomic response that is triggered every time that I get my hands dirty, which makes my nose or eye itch. I've heard that others experience this odd phenomena. I guess that I am just not neat enough. At least oily tools don't rust as fast. That said, after I sharpen a tool I wipe it OFF using an old towel and then typically wipe ON a light oil. Talk about two faced. It is CLEAN oil, I suppose.
Mystery brown, soft Ark?, surgical black, medium Ark?, slate.
Also, as I may have mentioned, I found these stones to be more effective after creating a VERY thin slurry using a diamond stone. With no slurry they felt pretty lifeless, like not much work was being accomplished. So if you assume slurry, I'll spare the "before" photos.
Here is the medium Arkansas? with an example of a thin slurry. This was enough to completely change the feel of the stone.
Soft Arkansas? I liked this one. Tolerably fast, good feedback and left a finish comparable to a 800-1000 grit waterstone.
I also tried using the side face of this stone to set the bevel on this old 1940's Japanese kitchen knife. My wife's grandfather brought it back after being stationed in Japan after WW2. It is laminated construction just like the chisel, with a very soft backing iron that tended to load up and clog the stone but was easily cleaned using soap and more water. It WAS quite a bit faster cutting than the top face, but slightly coarser, maybe 600 grit. Also interesting is that out of all of these stones, only the slate brought out the contrast between the hard steel and soft iron. The Arkies made the lamination line less distinct.
Medium Arkansas? A fair bit harder, slightly finer finish (1200'ish) but feedback was vague and the cutting action was pretty slow.
This mystery stone is a light/dark, mottled brown, possibly a hard Arkansas? So hard that neither Brandon nor I had the patience to do a first-class job of lapping it flat. It was probably a fair bit lighter in color before decades of oil and steel residue soaked in and turned it dark, and is not quite translucent. The grain structure seems more fine then the Novaculite. It is very dense and fine on the top face, kind of glassy feeling but polished nicely to around 3000 grit or higher. The side face was much faster and had better feedback, but again was more coarse at about 2000 grit.
This is a little slip of slate or very fine shale. VERY fine with faint sedimentary layers, this guy produced a finish of approximately 8000, and if continued, up to about 10000 as the slurry broke down. Speaking of slurry, this stone made its own, a very creamy viscous light gray and the stone was pretty hard for slate. A beautiful polisher, I would love a piece of this in a larger size. Brandon will keep this one for carving tools (smart man).
Surgical black Arkansas (with an Umehiro chisel) and lots of ODC slurry.
Different chisel, different slurry (diamond, I think)
This is a big, beautiful, surgical black Arkansas stone from Hall's sharpening stones. I was REALLY curious to find out what kind of edge I could get with this guy. VERY hard and glassy. Using water and no slurry, this stone had just a hint of feedback to tell you that it was doing something and gave a very polished edge, but felt more like burnishing than actual cutting. No depth to the look of the steel.
This stone has been used and lapped with diamond stones, but even so, STILL has the factory lapping/scratch marks visible! REALLY hard! Fortunately it is pretty flat and should stay that way, oh, pretty much forever. Do not let one of these get dished out!
Using a diamond stone to raise a slurry was a lot of work and the slurry did improve the feedback a bit, but as the slurry degraded, that was it. No new slurry was produced, the stone is THAT hard. It does cut though, just very slowly. I tried making slurry with a few different types of stone: bare (poor), diamond (this would be surgical black slurry, fair), soft Arkansas (good, but didn't last long enough), mystery brown (fair), slate (good for polishing), and ODC (volcanic tuff, good).
The best slurry was made using the ODC nagura and used in the classical straight razor fashion. Make up a fair bit and just keep at it, allowing the slurry to degrade and dilute until you are finishing on just the bare stone itself. VERY polished edge! This would be a good stone for razors and, like a true razor hone, you would just need a variety of slurry stones to get the type of edge that you want. I found it too slow for tools, with one exception. It is GREAT for lapping backs of chisels and plane irons. Because it is SO hard, you can apply all of the force that you want, with no fear of dishing out gouging the stone.
If you just want sharp tools without spending much money, you can't beat old oilstones. An old soft Arkansas (or an India stone synthetic), a hard Arkansas, and a piece of very fine slate would be perfect for classic carbon steels. Some say that once treated with oil, they are ruined for water use forever. That MAY be true to a degree, but is mostly a load of crap. They still do work. They work well enough for me, anyways. Old, used ones are ridiculously cheap because they are not currently "cool". What you get is sharp tools forever and a stone/tool that will last for GENERATIONS! There is NO higher ROI (return on investment) than that of sharpening stones.
Fancy, new steels need more extreme measures, but I don't need that stuff. It WILL get dull sooner or later, and then you need to sharpen. Have fun with that! Learning to sharpen, REALLY sharpen, had been the MOST valuable skill that I have learned. I can't emphasis this enough, it has been a game changer. I wish that I had learned sooner, like 30 years ago. Back then I just wanted to build things, not spend a bunch of time polishing edges. I mean, if it cuts wood, it's sharp enough, right?
I feel like I've been sitting in a dark room and have just figured out that there is a light switch. What will I see when the light comes on?