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Red Green
The sumitsubo is a Japanese marking and layout tool similar in function to the Western chalk line. Although few Gentle Readers in Western countries have experience using this tool, it has much to recommend it.
In this post we will briefly examine this tool so prevalent in Asia. Our focus however, will be on the traditional wooden versions, not the modern plastic one, a version of less beauty but perhaps more utility
Sumitsubo is written using the Chinese characters 墨壷 which directly translates to “ink pot” and pronounced “sue/me/tsu/bow.”
The inkpot has been a common tool in many Asian countries since ancient times. Indeed, until recently, few craftsmen in Asia had even heard of the dusty chalkbox used in the West.
This is just conjecture by your humble servant, but the fact that nearly all writing and much artwork in many Asian countries during recorded history relied heavily on brushes and sumi ink, the black carbon reside of burnt pine sap, may be the reason the inkpot became the standard tool for marking straight (and sometimes intentionally curved) lines.
Using the Sumitsubo
The sumitsubo works on various surfaces including wood, stone, concrete, gypsum board, and other construction materials. It is not unique to Japan, but is found in one form or another throughout Asia. It is an essential tool for carpenters.
A thin line spooled around a reel attached to the sumitsubo passes through holes at each end of a “pond” or inkwell filled with absorbent silk or cotton waste soaked with ink. As the line is let out, and with encouraging pressure applied by the user, it soaks up ink from the inkwell.
In Japan, a wooden bob called a “karuko” with a sharpened steel pin is attached at the line’s far end. The workman pushes this pin into the surface of the wood being marked to secure the end of the line in place for marking.
To use the sumitsubo, the workman stretches the damp inkline over the surface of the object to be marked, secures it in the desired position at the far end using a pin, weight, or helper, reels out and stretches the line, picks up the line with his fingers and releases it snapping an inkline. There are other more subtle actions that the user must perform at the same time, but this is the essence.
Depending on the user’s skill and the available line, a perfectly straight line can be marked on a flat, level surface to many meters in length.
The ink line has several undeniable advantages over the Western chalk line. First, the line it leaves is narrower and less “ fuzzy,” sufficient for fairly accurate carpentry work, much more precise than the typical chalk line.
Second, it is not as easily rubbed off or blown away as chalk.
Third, while inks of various colors can be used, black is most common and contrasts nicely with most building materials, but red is another traditional color. Nowadays, ink can be purchased in a rainbow of colors, some in permanent ink and even some that glow-in-the-dark.
The standard variety of ink used with sumitsubo is not entirely waterproof and if applied to a non-absorbent material like stone or steel, will not endure a rainstorm well. There are waterproof inks available, however, and of course the standard trick of using a spray can of clear lacquer to seal the snapline works as well with ink lines as it does with chalk lines.
History and Design
As your humble servant has mentioned in previous articles, the marketplace development that makes it possible to purchase completed woodworking tools is fairly recent. In previous centuries and millennia, when material costs were high and labor costs low, craftsmen would commission a blacksmith to make the metal components of their tools, but would make the wooden components themselves. In Japan at least, the sumitsubo too was made by the individual craftsman and became an opportunity to display both his skills and imagination, yielding unique, beautiful, and even bizarre tools.
There is neither adequate time nor space in this insignificant little blog to go into the evolution of sumitsubo design in any detail, much less the design variations, but the Takenaka Tool Museum’s website has pictures of representative examples.
The style used for the last 200 hundred years or so is shown at the top of this post, and in the photo below. The major improvements include a larger ink pond designed to both hold more ink and to better accommodate the bamboo sumisashi inkpen used for layout, a larger, more exposed reel to hold more line, making it quicker to reel in, and providing better ventilation to reduce mildew, and a narrower, easier to grip tail containing the reel greatly improving functionality and reducing fumbling and damage.
The carving seen in sumitsubo has meanings, of course, which varied with the craftsman and popular whim. The most popular style nowadays has a turtle and a crane facing each other across the ink pond. In Japanese mythology, both are considered lucky, with the crane said to live 1,000 years and the turtle 10,000 years. The turtle normally has a hair skirt flowing behind.
Dragons are another mythological motif seen in sumitsubo, being a fierce but noble and benevolent creature in Japanese tradition
The reel end of the sumitsubo typically incorporates water or wave details, perhaps related to the ancient Japanese motif of wagon wheels in flowing water.
The last sumitsubo maker in Niigata Prefecture was Mr. Tamaki (RIP). Those Gentle Readers who have visited Kezuroukai competitions in Japan may have seen him doing exhibitions. Here is a link to a video of him making sawdust.
Here are a few links to videos of sumitsubo in use: Link 1 Link 2 Link 3
Here is a link to a video of a huge (2.3 shaku = 700mm = 27.4″) sumitsubo by a famous Niigata craftsman named Ichimonji Masakane. The size brings the carving details into focus. This is of course not a practical tool, but was created for decorative purposes. Once, every major tool store had a similar sumitsubo on display. If you visit Suiheiya in Tokyo you can see similar examples.
The sumitsubo is a tool Western woodworkers could benefit from when making straight layout lines because it’s not only cheaper, more convenient and more reliable than a long steel or wooden straightedge, it produces a finer, easier to see, and more indelible mark than a chalkbox can.
The sumitsubo was once said to be the symbol of the master carpenter, the craftsman that created the design and performed layout of major aspects of a construction project. Even today, older carpenters prefer the wooden sumitsubo and inist that it does a better job. I suppose every generation in human history had similar attachments to older ways and older tools. But I have a hand-carved Zelkova wood sumitsubo mounted under the lid of my toolbox. Does that make me an old fart?
A drachma for your thoughts.
YMHOS
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Covington & Sons Tools 
Great write up, and I love the Red Green quote opening. 🤣
Something I’ve been wondering is how long does ink last before it dries out in a sumitsubo? I’m a hobbyist so I wouldn’t be using it daily, as much as I’d like to be — my job ends up commanding most of my time. Haha.
I’ve been debating the trade offs recently between exploring a sumitsubo, a fine point pen or a marking knife.
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Good question. It depends. It used to be that a craftsman wanted his ink to dry quickly to avoid fungus growth. Modern inks usually contain anti-fungal chemicals so they can remain wet a long time without growing fuzzy and walking away. This is especially important with the modern plastic sumitsubo with better containment and which dry slower. If you won’t use it frequently, a plastic sumitsubo like those made by Tajima work best when combined with commercial inkline ink. That’s what I have used for decades. Not sexy like Brian Holcombe’s planing robes, but practical. In any case, it is best to store a sumitsubo you want to stay wet in a plastic bag. Fungus can still happen so be careful in warm, humid climates. Stan
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I wondered about the ink drying out, too. If it does, just add water or is another solvent better?
I also would like to know more about using a bamboo marking pen with a sumitsubo. I’ve seen videos of carpenters dipping the pen in the sumitsubo pool to ink mortise and tenon layout lines. But I have not yet found information about how to make the pens.
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When you first attach a line to your sumitsubo you need to do some simple prep. First, soak the line in a bucket of warm water and a little dishwashing detergent. Don’t put it in a washing machine unless you intend to donate the line to your cat as a toy! Ah memories….
Then, before the line is entirely dry, thread it through the pond and roll it up onto the spool. With the spool removed from its axle and lifted out of the body, drip ink onto the line. Don’t make it dripping wet, just saturated. Replace the reel. Add ink to the wadding and away we go.
If the ink has dried, adding water and prodding the dried wadding with your sumisashi pen will usually get it working again, but eventually the mark will become too grey, so you will need to add more ink. Please use ink intended for sumitsubo, not the cheaper stuff sold for calligraphy.
Sumisashi are clever tools. You must use one to make a traditional open sumitsubo function. They won’t replace a marking knife, carpenter’s pencil, marking pen, or ball point pen for some tasks, but for timber framing they are the bee’s knees. Even when timber framing, a carpenter’s pencil with a chisel point and red and black marking pens are necessary IMO.
There are lots of videos on NoobTube about making sumisashi. You need bamboo. Here are a few.
In this video, notice how he uses the heel of the wide end as much as the toe. Much stiffer and more precise. Notice also how he uses the narrow tail end to write column line and other marks designating location where the member will be installed in the frame.
Here’s Bayashi23 making a sumishashi. Not quite as down and dirty as the other version, but the results are good. https://www.youtube.com/watch?v=J9HCxeTwkfY
This video is by an instructor at a woodworking technical school. More details about how to use.
BTW, here(s a cool video I just found of a guy planing a daikokubashira, the most important post in a building. Nice work. https://www.youtube.com/watch?v=PdtbFSnwq3c
A well-done video of a guy laying out and cutting a shachihiki toyuutsugi joint using a sumisashi, handtools and powertools. FYI, after the Kobe earthquake, this connection is not permitted for structural purposes without steel hardware reinforcing it. It’s clever and looks cool, but removing that much wood leaves the joint relatively weak and very susceptible to rot. https://www.youtube.com/watch?v=H5d_mTj0xkM
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Something I have been wondering about for a while re: sumitsubo and sumisashi is the relationship between the ink line and the intended cutting plane. Since an inked line has width, one has several options as to where cut relative to the line (inside edge, outside edge, through the center-line). Is there a standard practice in Japanese carpentry regarding where a tool engages an ink line across its narrow width? Thanks.
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An excellent point. I think the correct answer will depend on the craftsman and the situation. One solution, of course, is to split the layout line. The other is to select one side of the layout line and cut so as to leave the layout line in place. In the case of a mortise connection, for instance, this may mean to cut to the inside of the line for the mortise hole, leaving the line intact, Of course, assuming the same dimensions are applied to the tenon, it too must be cut inside the layout line minus half a whisker. The craftsman needs to make some layout rules/procedures for himself and apply them consistently. For general carpentry, I think most people aim to consistently split the line. On the other hand, the inkline has width, as you observed, so there are limits to how precisely one can layout of cut using an inkline. Where greater precision is required, marking gauges with knife blades and marking knives are a better solution. Stan
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Where can one purchase the proper ink? I am in the US and I have looked on eBay and Amazon and have only found the calligraphy inks. Hida tools have Sumitsubo but I have not found ink there.
I have read that the ink contains rabbit skin glue in addition to the pigments.
I would try to make my own if I had a formula but would much prefer to purchase it.
I’m looking to attempt some timber joinery and I see a real advantage to a thin accurate line as opposed to chalk that will be rubbed off in the process of cutting the joints.Knife lines need a straight edge and are more of a juggle for me than snapping a line.
Thank you for the articles and your time.
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I’m in Tokyo and have never purchased sumitsubo ink overseas. Bur it appears Highland carries it. https://www.highlandwoodworking.com/blackinkfortajimaink-ritesnapline.aspx
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I’m left handed, & have used right-handed sumisashi for years, but recently made some left-handed from bamboo in my yard. The bamboo is not quite big enough so the pen is narrow. I’ll look for larger bamboo.
Do you come across this?
Also, sumi tsubo with a crank is strongly right-handed, with the crank in the way of the hand and cannot be easily reversed. What do left handed Japanese carpenters do?
To Gregory Smith above, I have purchased ink from Hida- years ago, but I think they have it currently. Might have to call.
Cheers, Jay
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For sumisashi, you really need the bigger sections of bamboo, as you noted.
I have never seen a left-handed sumisashi or sumitsubo, although I have no doubt craftsmen have made them for their own use. It was once SOP for carpenters to make their own sumitsubo, of course, and when human creativity and imagination are set free interesting things happen. In fact, some pretty wild examples survive in collections.
Regarding left-handedness, the Japanese see it as almost a birth defect, disapprove of it culturally and train their children out of it.
Another option is to adopt the sumitsubo detail common to Western Japan of no crank, just use the palm to directly rotate the reel. They have a point: the crank is often clumsy, inconvenient and functionally inferior. But the same can be said for most human endeavors. Best of luck.
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Thank you for your comments about sumi tsubo & left-handedness.
Much appreciated. Jay Wood
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