Machines for grinding ink

Grinding solid ink sticks to make ink can be a time consuming task, especially if you need a lot of ink (such as for larger works, or lots of practice). This is why ink grinding machines (墨磨機) were invented. While there are different models from various companies, such machines usually come in two types, which I will be touching on in this post.

The first type is the revolving type. Here, an ink stick is held in place and the ink stone revolves under it, grinding the ink. (There is also a version where the ink stone is stationary, while the ink stick revolves above it.) Here, the revolving "ink stone" is usually not an actual ink stone; that would be too heavy and require too large a motor to drive efficiently. Instead, it is usually a round plate with a grinding surface inside.

Model SS Sumi-suri Shokunin (墨磨職人) from 墨運堂

 

The advantage of such a system is that the walls of the grinding plate can be made higher to hold more water. This means more ink can be made at one go. The disadvantage is that the grinding plate is a consumable; the grinding surface wears down over time and eventually, you need to get a new grinding plate. Of course, such replacements probably take place once every few years or even decades. The problem is, the company may no longer be making such parts or even be in business by then, which is a risk that you have to take when using consumables. (For the revolving type where the ink stick is the one that revolves, there is no such issue and the ink stone used is usually a normal round ink stone.) Another issue is that the mount holding the ink stick usually cannot hold ink sticks beyond a certain size.

The other type is the piston type, where the ink stick is mounted on something like a piston, which is then used to move the ink stick horizontally back and forth on an ink stone.

Tetsujin (鉄人) from 墨運堂

The advantage of such a system is that you can use a normal ink stone (but it has to be quite large) and the mount can usually fit most ink sticks, even very large ones. You are more or less getting the same ink as if you are grinding it yourself, although you cannot really vary the amount of force being applied. Another disadvantage is that the amount of water that an ink stone can hold is usually quite limited; if you need a lot of ink, you may need to grind in batches. Piston-type machines are also much larger than size compared to the revolving ones.

Here is an example of the revolving type. It can hold up to 40ml of water, so I usually run it for 2 hours, then dilute with another 40ml of water to get about 80ml of normal-concentration ink.

For the piston type, while my ink stone can hold about 20ml of water, the piston action causes the water to splash all over the place. So I usually use only 15ml of water, then run the machine for 2 hours too. After which I dilute it with 65ml of water to again get 80ml of normal-concentration ink.

In the end, the sweet spot is around 2 hours of running the machine. This gives you about the same amount of soot and you just need to water it down. For the piston type, running it beyond 2 hours gives ink that is too thick to "collect" from the ink stone. Meanwhile, I am sure I can run the revolving type for 4 hours with 40ml of water, then water down with 120ml of water to get 160ml of normal-concentration ink. I try not to do that, though, because the motor may get too warm from continuous operation; in the end, I run it for at most 2 hours, then give it a break if I need to run it for another 2 hours.