After four years and the formulation of 81 different recipes, they finally developed a suitable injection formula through repeated improvements.

With the "prescription" in hand, the next step was how to apply it.

Fan Zaixuan, a member of the cultural relics protection team, has been involved in the restoration of ancient murals for 43 years.

He explained that mural restoration demands extremely precise work and allows no room for error. Conventional tools are inadequate for mural restoration, so the team designed their own restoration instruments.

They replaced the plunger of a traditional syringe with an ear syringe, creating a device that looks like a needle with a balloon attached at the bottom.

"This was to allow for more injection material and to better control the injection volume," Su explained.

After eight years, the bottleneck issues in Cave 85 had been resolved.

"This was a process of going from zero to one," Su said.