Vietnamese Natural Lacquer is produced mostly in mountains of Phu Tho province, which located North West from Hanoi. The climate which never goes down 12 degree C even in winter, and the red soil in this region are said to be the ideal condition for Lacquer plantation. The element of Vietnamese lacquer which gives itself a beautiful glow, durability and cohesiveness is called Laccol, while respective element in Japanese lacquer is called Urushiol. The lacquer trees in these two countries are two different spices. Japan imports Vietnamese raw lacquer in small scale but it is considered as low quality lacquer which gives poor glow and dries too slowly. However, these problems only arise to Japanese craftsmen who work under less humid atmosphere. To be precise, lacquer does not dry but it hardens by chemical reaction with moisture in the air. Therefore, significantly humid climate in Northern Vietnam is ideal for Vietnamese lacquer. If craftsmen use Japanese lacquer in Vietnam, it will dry too fast for them to work with.
The inferiority of glow derives from the fact that Vietnamese lacquer contains less magic element described above and it contains more gum. As a matter of fact, this is also a great advantage for Lacquer Painting technique. The gummy substance helps lacquer to stay soft enough for artists to sand complex layers smoothly.  The enzyme within lacquer continues to cause chemical reaction with the help of gummy substance even after artists finished their work. Therefore, clarity, glow and hardness of painting enhances as time passes.
As you can see, Vietnamese Natural lacquer is mysterious material which breathes just like us and it ages just like quality wine.