#2101 Narutaki Giant Iromono tomae
Air Raid Shelter stone

This stone is what is called a Grade (size) #24 toishi which means that an average
adult person who worked at the old mine sites could carry 24 of these stones in
a back carrier down the mountain side to the work shop below. Grade #24 stones
are at least 218mm long x 78mm wide with a thickness that is appropriate to the
shape of the stone.

A really excellent knife or tool stone the iro mono pattern is made upof kiita yellow
and aka red in a cloudy or foggy background. The kiita color is very clear and
matches up perfectly with the best kiita tomae strata stones. Only medium hard
it will self slurry with a blade like a knife, chisel  or plane blade.

The sides and ends are shaped using hand saws, the back is hand chiseled
with a geology hammer of the kind that was common for stone workers to use
up until the 1950s. The top has been lapped and polished and the top edges beveled.

With a splash of clear water the stone when used with a knife or tool will peal away
black steel swarf easily leaving the hard steel of any kind leaving a shiny chrome
surface. If a slurry base is created the cutting powers are accelerated and the
slurry turns jet black in just the first few strokes as you can see in the video below.
I have also honed several western straight razors on this stone which produced
very keen edges resulting in barber close shaves.

All of the stones in the Air Raid Shelter were from the same era
but I suggest several different mines. Each stone is totally unique
to the other and are not like any processed stones that I have
found in the past 39 years that I have been buying natural
stones from Kyoto. These stones were cut and finished, judging
from the hand cut saw sides, before 1920 and most likely in the
Meiji Era from 1850s to the early 20th century. The colors, shapes
and granular patterns of the hoard are much more organic then the
20th century stones that most of use are familiar with. I have found
and you will feel by testing this stone that the sharpening qualities
are not like the plain monolithic generally colorless stones that are
on the market in this first quarter of the 21st century. These stone
have all been superior in both cutting speed and fineness to the
modern processes stones and the hardness factor is a notch below
the current flood of stones too. These stones are very much
User Friendly as my clients are reporting back to me.

I would recommend that any and all of the Air Raid Shelter stones
be sealed on the sides and the ends and the backs could be an option
if any vulnerable cracks or inclusions appear. I will be willing to do this
for you is you wish.

The stone (toishi) has been lapped perfectly flat and the corners and
edges beveled unless otherwise noted.  All of my stones come with a
tested and appropriately sized tomonaguara slurry stone, and a money
back guarantee minus the return shipping.
All stones are sold with a
money back guarantee
minus the return shipping.
Grit Fineness
9++ to
with slurry
Size 232-87-58/60
in mm
Price $3200

    Japanese Natural Stones sharpening characteristics.

    H or Hardness Scale Explanation.
    H Level 6-8 is medium hard and these stones will self slurry under a blade with pressure.
    A drop of water placed with a finger tip will sit proud for one minute and then begin to
    flatten and seep into the stones surface, within five minutes the drop will be gone.
    When using a diamond plate (DP) to lap or make a slurry the action is easy and fast.

    H Level 9 is hard and requires concerted pressure and effort upon the blade to self slurry.
    A drop of water will sit proud for one half hour and then begin to soak into the surface.
    With a DP the stone feels hard and the slurry is thin even with 10 strokes.

    H Level 10 stones are the hardest and will not self slurry even under extreme hand pressure.
    A drop of water will sit proud and round on the surface for one hour or more.
    A DP glides over the stone, abrasion happens but very slowly and only with much pressure.

    PS or Particle Size Scale Explanation.
    PS Level 1-3 (500 to 2,000 grit) for bevel creation are best found in synthetic stones
    or with greater difficulty using Arato coarse stones from Japan from areas outside Kyoto
    or from individual or successive nagura types stones with appropriate grit levels.
    At this grit level steels will brighten but with dull finishes. With laminated blades some
    contrasting finishes can be created especially if slurries are utilized.

    PS Level 4-6 (2,000 to 4,000) leave medium deep scratches that are easily removed.

    PS Level 7-8 (4,000 to 8,000) leave finer scratches that are easy to remove and difficult       
    to see with the naked eye but can be seen with a quality 15x loupe. These stones can
    a high carbon steel blade looking like polished aluminum to dull chrome.

    PS Level 9-10 (8,000 to 25,000) leave the finest scratches at the lowest levels ie. 8k to 12k
    of particle size are difficult to see with 15x, under most optical microscopes at 100x are    
    easier to see. The scratches at 12k to 25k or natural stones judged to be on par with
    these grit levels are difficult to see beyond the 15k level with most optical glass.
    The carbon steel or stainless will be bright and polished like a mirror.   

    S or Cutting Speed Scale Explanation.
    S Level 1-5 at the lowest level have no abrasion power but instead act as burnishing
    stones and the upper 5 Level are very slow to abrade tough steel.

    S Level 5-7 will cut steel and remove previous scratches easily.

    S Level 7-9 will cut steel and remove previous scratches easily and quickly.

    S Level 9-10 will excel in the above and at the 10 level will amaze.
    Cutting speed can be quantified for personal reference by stroke count.

    Japanese Stone Sizes Explanation
    Stone sizes in Japan are in millimeters and referred to as "grades" and the sizes stated are
    the minimum dimensions which takes into account variables in Length and Width only.
    This grade system has its roots at the mine entrance, and is based on a working adults
    ability to carry a certain number of grouped and graded by size stones down an average  
    mountain trail on his/her back to the valley floor. Working adult refers to a man of average
    strength. Women and children also labored but some adjustments of course made.
    Grade             Length     Width              Equivalent in inches.
    #24 pieces     210mm       78mm             8.26         3.07
    #30                205             75                  8.07         2.95
    #60                185             70                  7.67         2.75
    #80                180             63                  7.08         2.48
    #100              160             58                  6.29         2.28
    Razor            136              82                  5.35         3.22
    Koppa            are by definition bits & pieces and are usually in small sizes

    Sharpening Characteristics Explanations.

    If all things are equal: a grit rich or silica rich stone will remove a measured amount of
    steel faster than a grit poor stone will.
    A soft grit rich stone will remove a measured amount of steel faster than a grit poor
    hard stone.
         Like wise if all things are equal: a coarse stone will remove a measured amount of steel
faster than a finer stone will.
    In the same vain a slurried stone will remove steel faster than a non slurried stone will.
    And again a stone used under running water (that rinses away any loose grit/slurry particles)
    will act finer than a stone with standing water, with or without a slurry.

    Japanese natural sharpening stones are unique in the world of sharpening for handfuls
    of reasons and one of those is their ability to take on different characteristics while in a
    state of being used dry, wet, with a slurry or under running water like at your kitchen sink.

    One example of this would be that if any one particular high Hard Level Jnat (Japanese Natural)
    is used dry and without water their sharpening qualities are diminished and they will act more
    like a burnishing stone, but if that same high hardness level stone is used wet it will act as an
    abrasive stone. The same goes for coarse stones. Japanese awase-do (aka awase-to, tennen
    toishi) really only cut with advanced actions when wet.

    And about to slurry or not to slurry. A slurry comprised of loosely bound grit particles suspended
    in water, often acting as bundles of bound grit will act coarser and cut faster strictly depending
    upon the mechanical action that created the slurry. A #400 diamond plate will make a coarser
    acting slurry than a #1200 diamond plate. A nagura or slurry stone cut from a similar piece of
    tennen toishi can if harder than the base stones encourage the base stone to contribute slurry
    more freely, or if the nagura is softer it will itself provide the majority of slurry particles. This is
    the principle for which the Nagura Progression System is based and this system will only work
    marginally well with other base synthetic or natural stones like Coticules, Arkansas and the other
    slate stones.The Japanese dedicated natural nagura tend to favor being paired with the natural
    awasedo found near Kyoto because both the base and nagura components will encourage the
    crush of the clays that release the silica grit of each other.

    In all the world the Japanese tennen toishi are unique because of the slurry component and the
    way it can be exploited. For centuries the clay binders that comprise the glue that holds the
    stones grit in place has been manipulated by sword polishers, carpenters and barbers to suit
    their needs and requirements. No other stone will react with such characteristic and predictable
    ways as the natural stones that the mountains in and around Kyoto offer.

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                        cannot be duplicated without written permission