Sealing Nagura

Full Nagura Set Sealed 1

Sealing Mikawa Nagura might seem superfluous. While some people feel that these stones don’t need to be sealed, I believe that sealing them can only be a good idea.  More often than not, I soak my Nagura a bit before using them, and when I’m honing my hands are always wet – these stones get soaked and dried repeatedly each time they’re out for a honing session. Sealing them keep the tops and sides dry which will help prevent them from crumbling. 

I’ve had a few Nagura shed small bits from the sides of the stone. A few times, I was lucky and managed to notice before the edge ran into the pebble. A few times I was not so lucky and it created a lot of extra work.  I hone a lot – so I’d like to avoid this as best possible. Some Nagura seem to come with built-in distractions; small holes, little fissures, cracks, sand lines, etc.  Sealing all of the above seems like a good idea to me and I believe it’s worth the added effort. 

Another point is that the Asano Stamps are prone to wearing off over time, and continued wetting and drying exacerbates this. Protecting those ink stamps is important to me; it’s a visual aesthetic and a historic concern also. That mine is closed, the new pieces on the market are being cut from existing stock, and at some point there will be no more Mikawa Nagura to stamp.   

In the past I was sealing the stamps with garden-variety clear nail polish. It’s inexpensive, and it seems to work pretty well. Recently though, I’ve moved towards sealing all Jnats and Nagura with Cashew Lacquer; it’s stronger, and it’s more of a traditional type of approach. 

Cashew lacquer is not easy to purchase here in the USA, and it is significantly more expensive than nail polish. Cashew has a pungent odor, it’s a bit difficult to apply, and it takes a while to cure. Sounds like fun, eh?  

Right out of the can – Cashew is too thick to use properly.  It can be used like that, but it will go on very thick and getting a nice looking and even layer is nearly impossible. A 50/50 mixture of Cashew and high quality turpentine from an art store is a good starting point. Starting out thinner is better than having it too thick. You can always adjust the mix but if the first layer on the stone is too thick it won’t look good. 

When mixing or applying Cashew, I highly recommend using gloves, in a properly ventilated area. The lacquer is quite pungent, and so is the turpentine. I make the mix in a very small mason jar, which works well. To transfer the Cashew from the can to the jar is tricky, pouring it out of the can will create quite a mess. I use a wide straw, but I’ve been told that disposable cake icing syringes are good to use also. I put the Cashew in the jar first, then add some turpentine and mix slowly with a cut down chopstick. Letting it sit for a day or so seems to help it dissolve better, which helps me get a smoother coat. I haven’t perfected all of this yet, but it’s coming along pretty well.  

After the mix of Cashew/Turps is set up,  I’ll stir it up a few more times to make sure it’s as smooth as I can get it. For applying the lacquer, there are ‘official’ Urushi brushes available, but I use a simple hobbyist grade paint brush. I do think a higher quality brush would help apply the lacquer more evenly though. 

The translucent Cashew isn’t clear, it’s actually a warm amber color. It’s said to be stronger than the colored semi transparent colors but I haven’t experienced any differences in durability or hardness. The manufacturer claims this is so due to the fact that there’s no pigment in it; the coating will be pure lacquer when cured. A base coat of clear followed by a coat or two of a semi transparent color is, theoretically, a good compromise. I’ve used red Cashew on Nagura and it seems to be very strong though – so I don’t know that the strength consideration is all that important when sealing stones. However, for my own peace of mind – I’ll seal an Awasedo with at least two coats of clear before I consider using any color on top. 

Mikawa Nagura, along with some Jnats and Tomo Nagura, are very porous. They will soak up a couple or even a few layers of Cashew before a good even coat remains after curing. I suppose a thicker mixture would help get the job done faster but I’d rather work with several thinner coats than fewer thicker layers. 

When fully cured, which usually takes a couple of days; I find that the lacquered surface is a tremendous advantage. It offers a bit more grip to the Nagura when it’s wet, and the stone just feels more ‘solid’.   

When all is said and done, the process is involved, not all that simple to execute, and somewhat more expensive than some other options.  

As my friend Nelson says - “Sometimes, the price of keeping it real is high.”

You can check out Nelson’s blog by clicking here

Click here if you have any questons or comments. 


© Keith V Johnson 2014 - 2018