storage of urushi-coated koshirae

[Marius]

Dear All,

 

what is your experience in storing urushi? I am acquiring an Edo koshirae in very good condition, and I would like to keep it according to the best practice. I live in a country where winters are cold and centra heating dries up the air a lot.

 

How should I proceed ?

[Veli]

Hi Mariusz,

 

This is a constant source of concern for me, too. I keep my blades and koshirae in a glass/wood cabinet, with a tight lid and consequently very slow moisture exchange with the ambient air. The moisture has to penetrate slowly through solid birch sidewalls, or through the plywood bottom. During the cold and dry season, I regularly insert a 30 cm lenght of clean wood that has been stored outside in a shed and thus has something like 30 mass-% of water in it. This piece of wood slowly evaporates moisture into the air inside the cabinet, and keeps the moisture at a tolerable level. I would hesitate to insert liquid water into the cabinet. The moisture will rise too much/too rapidly, and in the liquid itself there is a possibility of mold growth.

 

Recently I decided to leave one of my shinsa-destined blades behind when travelling to Tampa Shinsa, because the blade has koshirae only, and the rapid moisture change from 1% to 80% would probably have damaged the saya.

 

Despite of these measures, I prefer buying blades in shirasaya instead of high-quality lacquered koshirae.

 

Veli

[cabowen]

Many times I have seen a half full glass of water in the display cases at museums in Japan when lacquer ware is displayed....

[Marius]

Gents, do you think one could store urushi koshirae in a paulownia box?

[Curran]

Consider (cigar humidor) Humidity Crystals.

Also be careful of the container, as Veli discusses.

 

I spent almost half the year in New York City, and the rest of the year in Florida. Veli spoke of Tampa at the most dry part of the year. It gets much much much more humid during high summer.

My small collection travels with me, so I am careful about the humidity levels and shifts.

 

Collecting wine for a decade was an initiation into this, but antique wood and lacquer are a more serious game. Basically below the 25% and above the 70% level, be very careful.

I find even the larger paulownia boxes struggle a bit in the shifts.

[Lindus]

Interesting, I was under the impression that it was pretty much impervious to any thing. Have had some superb lacquer items in the past with no problems, is it that lacquer on Saya is different from say cabinets,Box's etc?. I live within a mile of the sea is that perhaps a problem solver.....

Roy

[Guido]

If the item is entirely coated with lacquer, i.e. the wood or paper or whatever is the core is thus sealed, exposure to light, especially sunlight, should be the only problem. The inside of a Saya, however, is raw wood that absorbs and/or evaporates moisture, which can lead to a cracked or warped lacquer coat.

[cabowen]

Here is a good explanation on why humidity and temperature changes can harm any piece of lacquer:

 

"Understanding this layering of material that is used in lacquerware gives us a better understanding of why environmental changes can affect it.The core of the problem comes from the substrate. Wood is the most common substrate for lacquerwork, but it happens to be an environmentally sensitive material. Wood will expand, contract and deform relatively quickly in response to changes in the environment and most specifically changes in humidity. In an atmosphere of higher relative humidity, wood will expand, and when there is lower relative humidity, wood will contract. Increasing the complications is the fact that wood will not necessarily contract completely back into its original shape or size after expansion resulting in distortion.Once urushi is applied to the wooden substrate and cured, it creates an effective moisture barrier for the short term. However, although urushi does create a good moisture barrier, it is not completely impermeable. When there is an imbalance of moisture on either side of the lacquer layer, water vapor will gradually diffuse through the the lacquer through the process of diffusion until the moisture is equalized on either side of the lacquer layer3. This process can take years depending on the thickness of the layer of lacquer and it is because of this slow nature of the process that typical fluctuations in humidity and brief immersion in water or fluid will not damage a piece of lacquerware.A problem can arise in two situations however. The first is when a piece of lacquerware is placed in an excessively desiccating environment. In this type of environment, the specific conditions will cause an extremely high moisture differential and more quickly draw moisture from within the core of a piece of lacquerware. Damage can in this way occur in as little as a few days to a few weeks. However, this type of environment is rare to encounter in most situations.The other situation where damage may occur is when a piece of lacquerware is moved from an area of high average relative humidity to a place of low average relative humidity permanently or for an extended period of time. Although the moisture equalization in this situation will take significantly longer–a few years to a decade–it can still cause irreversible damage. Japanese made lacquerware is often more susceptible to this problem because of the high average relative humidity of Japan. Wood seasoned in Japan will have its internal moisture equalized to the higher humidity levels of the country. Because of this, when a piece of lacquerware is brought from Japan to a country with a lower average relative humidity, the imbalance of moisture between the two sides of the lacquer layer will cause the wooden core to dry out4. In a case where this happens very slowly, and also depending on the species of wood used, the core may not shrink or distort enough to cause any problems. In this case, it is best to maintain the piece of lacquerware at the same relative humidity in which it has equalized. Attempting to return such a piece to an environment with a higher relative humidity may cause expansion of the wooden core and may cause cracks in the lacquer layer5.Nevertheless, such damaging changes in atmosphere and humidity would usually not be encountered by a typical admirer or collector of lacquerware and is more typically encountered by museums and galleries where the proper atmospheric conditions for lacquerware does not coincide with the proper atmospheric conditions for other artifacts. Even if a piece of lacquerware is to be brought to a place with a particularly low relative humidity, the general cycle of use will typically prevent damage as moisture from washing or from the hands during use will help mediate the problem. If a piece is to be left in storage for an extended period of time in such an environment however, it is best to leave a cup of water in close proximity of the stored lacquer piece to prevent damage. However, do not keep a piece of lacquerware immersed in water or leave a piece in an area of very high relative humidity for an extended period of time as excess water over the equilibrium may cause degradation by oxygen. For most Japanese produced lacquerware it is best to maintain a relative humidity of the immediate atmosphere of approximately 60%6.Furthermore, lacquerware that does not contain a wooden core is typically less susceptible or invulnerable to damages caused by changes in relative humidity. Substrates such as plastics or ebonite do not react to environmental humidity and will not be susceptible this type of damage. Dakkatsu kanshitsuwares will also be generally unaffected by changes in relative humidity.However, most types of lacquerware are susceptible to damage from another environmental factor. In a very similar reason to the damages caused by changes in humidity in lacquerware with a wooden core, frequent, large changes in temperature may damage a piece of lacquerware. This type of damage is not bound to specifically a wooden core, but to various other juxtapositions of materials in a piece of lacquerware.

 

As seen in the earlier diagram, the layers of urushi in a piece of lacquerware are frequently not homogenous. Different materials are combined to create the piece as a whole. While most of the materials used in lacquerware will not have this problem certain plastic substrates as well as some inlaid decorations may be susceptible to this type of damage.

 

Damage caused by changes in temperature are also caused by expansion and contraction of materials but in this case, not specifically of wood. All materials have a different rate and amount of expansion when subjected to temperature changes. When two materials are bound together but tend to have different rates or amounts of expansion, problems may arise. One material will expand or contract differently from the adhered material causing delamination or cracking of the material. This may happen to the lacquer layer in general or specifically to inlaid decorations.

 

Such damage, however, is exceedingly rare and generally care must be taken only for highly decorated inlaid wares or low quality lacquerwork which use a plastic core.

 

In general practice, many of these problems will not occur. Harsh changes in average relative humidity or frequent, large changes in temperature are difficult to encounter in the every-day use of a piece of lacquerware. Nevertheless, care should be taken, and the general knowledge of what can damage a piece of lacquerware should be known to prevent damage if the situation arises. However, this care is very simple and should not require a radical change in behavior or use of a piece of lacquerware."

 

….

 

read more please visit http://www.hakuminurushi.com

[DirkO]

Here's what the Bishop museum in Hawaii thinks (no idea where I got this .pdf):

 

Urushiconserving.pdf

[Guido]

Here is a good explanation on why humidity and temperature changes can harm any piece of lacquer: ...

A good explanation indeed - at least in theory. However, not being aware of all that, my Inrô and other lacquer wares didn't care, and survived constant changes in relative humidity between 5% and 90% sor far without the slightest damage.

[cabowen]

A good explanation indeed - at least in theory. However, not being aware of all that, my Inrô and other lacquer wares didn't care, and survived constant changes in relative humidity between 5% and 90% sor far without the slightest damage.

 

Let me repeat the relevant section:

 

"However, although urushi does create a good moisture barrier, it is not completely impermeable. When there is an imbalance of moisture on either side of the lacquer layer, water vapor will gradually diffuse through the the lacquer through the process of diffusion until the moisture is equalized on either side of the lacquer layer. This process can take years depending on the thickness of the layer of lacquer and it is because of this slow nature of the process that typical fluctuations in humidity ...."

 

 

Perhaps the time at the different humidity levels in your situation is relatively short and precludes significant diffusion, or perhaps your time horizon is a bit short to make an accurate assessment as it can take many years in some cases before any effects are apparent, or perhaps you are just lucky, so far....

 

The important fact is that lacquer is not completely impermeable, so regardless of whether or not the base is completely covered or not, humidity and temperature fluctuations as noted in the article can be harmful.

 

So unless one is lucky or simply likes to tempt fate, maybe it would be a good idea to heed the above and take steps to properly care for one's lacquer treasures, in all forms....

[Justin Grant]

When I built the display case for my armor, I did not seal it 100% from the outside air. It is sealed pretty well, and I put in a thermometer and hygrometer. It will tell me the inside and outside temp and the humidity. If the humidity drops lower than the room I can add a humidification device like they use in a humidor.

 

The goal was to allow the armor more time to react to the temp changes and not a blast of cold or heat, but a gradual change. A drastic change will cause the urushi to crack and flake off, and once this happens, it is all down hill.

[Guido]

Let me repeat the relevant section:

Thank you so much! True, with me one can never be sure if I actually read beyond the first sentence of a post.

Perhaps the time at the different humidity levels in your situation is relatively short and precludes significant diffusion' date=' or perhaps your time horizon is a bit short to make an accurate assessment as it can take many years in some cases before any effects are apparent, or perhaps you are just lucky, so far....[/quote']I'm schlepping around at least 3 of my Inrô since 1988 through 8 international moves. I guess I'm really lucky. Let's call it dumb luck in the light of the (partially twice) qouted article.

[cabowen]

Let's call it dumb luck....

 

Ok, that works for me....

[Marius]

Sorry Gents,

 

I miss a conclusion regarding storage of urushi coated items in paulownia boxes... Forgive me if I am too insistent, but I have a beautiful tanto koshirae and a paulownia box (scroll box) and the two fit ideally.