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Surprising part of lacquer in that it dries better with more humidity


Lacquer has strange characteristics which exceed the imagination. Due to the unique characteristics of lacquer, the higher the humidity, the better it dries. Also, once it dries, it becomes a hard substance that cannot be dissolved again.


These abilities have something to do with the main ingredient of lacquer called urushiol. Urushiol is closely associated with the unusual characteristics of lacquer.


Lacquer does not dry in a usual manner
Normally, the drier the air gets and the higher the temperature becomes, you would think that the moisture content of the liquid would better evaporate and solidify. But, lacquer does not solidify in this manner.


At zero degrees Celsius (32F) when water becomes a solid, lacquer stops solidifying. When the temperature gradually goes up, lacquer will start drying.


But it only dries up to 40 degrees Celsius (104F). If the temperature goes over 40 degrees Celsius, lacquer will stop drying. This state continues up until 80 degrees Celsius (176F). Once it goes over 80 degrees Celsius, lacquer will start dying again. Lacquer dries or stops drying depending on the temperature.


The time required to dry significantly varies according to the location and climate where you apply the lacquer. Typically, it is said that lacquer dries in five to six hours, but this depends on the conditions when collecting the lacquer as well as its refining method.


Furthermore, it poorly dries in cold regions such as Aomori Prefecture. It will not dry in hot and dry areas such as the desert. So where you apply lacquer is also critical. This is why the quality of lacquerware with coatings performed in Japan is different from the ones with coatings performed in other areas even if the same lacquer was used.


Lacquer dries differently according to the conditions, and there are seasons in Japan when lacquer more easily dries and other seasons when it does not dry well. Lacquer is difficult to dry in the winter, but it dries well in the rainy season.


This is due to urushiol, an ingredient in lacquer. Normally, the moisture content evaporates and then dries, but lacquer does not dry in this manner. When lacquer absorbs oxygen, it undergoes oxidation and transforms from liquid to solid due to this chemical reaction.


Thus, a certain level of humidity is required in order for lacquer to dry. Because humidity promotes an oxidation reaction, it dries best during the rainy season. The fact that lacquer has difficulty drying in winter is largely affected by both the low temperature and the dry air.


Adjusting the drying speed
For lacquer, which dries in an unusual manner, you can adjust the drying speed. For instance, in cases where the drying process needs to be expedited, an oxidizing agent is sometimes added. This is because lacquer solidifies due to an oxidation reaction as described earlier.


At other times, water or alcohol is added. Water or alcohol is sprayed into a tightly-sealed container in order to make it more humid and then the lacquerware is put inside the container to dry. Compared to the case where an oxidizing agent is added, this method enables the lacquer to dry effortlessly.


On the other hand, there is a way to delay the drying process. When lacquer is exposed to temperatures at or above 100 degrees Celsius (212F), an enzyme, which is associated with an oxidation reaction, will be inactive and lacquer will stop drying. By mixing this “non-drying lacquer” with normal lacquer, you can delay the overall drying speed.


For example, in making lacquerware, sometimes powdered gold is scattered or other decorations are added. If you take too long for this step, lacquer will solidify and you might not be able to create the work the way you envisioned. Once lacquer solidifies, it will never go back to its liquid form, so you will need to start from the beginning.


In order to avoid such situations, it is important to delay the drying speed of lacquer. Lacquerware is created while considering the climate of each case.

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