It took countless days to prepare the wood for the firing process for making wood-fired teacups. The process of firing in a wood kiln takes hard labor over many days, requiring a constant feeding of the fire. The temperature of the firing must be controlled consistently at high temperatures (up to 1200 Celcius) to removes any unwanted elements and produces a stronger surface. The unique firing process results in unique marks of flame and ash which lead to beautiful distinct variations in color.
The ash falling on the glaze gives the surface a beautiful iridescent metallic appearance. Perfectly sized for gongfu style tea tasting. No one cup is the same as the others.
So why do you want to invest in a wood-fired teacup? If you are drinking tea with a lot of mineral flavors tea like oolong tea, a cup like this will improve and bring out even more of the minerality of the tea. If you drink green tea, it will take the astringency out of the green tea. If it's a black tea, it will soften the tartness you normally get from a black tea.
Unfortunately, it is not easy to know which tea works best with which cup. One thing for sure, avoid any herbals or flavored blended teas to use with the teacup. You don't want to leave the strong floral or fruity flavors in the cup. And only hand wash this kind of cups.