He used to rest every other hour while working, but now Kuang says he needs to rest every 15 minutes or so, and slap pain-relief plasters on his shoulders.

Although pencil is not the only drawing tool that Kuang has mastered, he insists on using it for his hutong drawings, saying, "The hardness and grayness of the pencil is best suited to drawing hutong's typical characteristics".

To make the picture more lively, Kuang sometimes adds small aesthetic touches, such as a birdcage or a stray dog at the entrance of a siheyuan. But he never compromises the authenticity of a hutong, saying being truthful to his subject is more important than artistry.

To record the look and feel of a hutong in different seasons, Kuang makes repeated visits to the sections he wants to draw. For example, he visited his favorite Yandaixiejie, or Pipe Street, more than 10 times, merging into the hutong scenery.

In winter, the southerner is armed to the teeth as he ventures out in his cotton-padded clothes and pants, 1.5-kg shoes, three pairs of socks, two pairs of gloves and a woolen cap that covers his whole face, save his eyes.

His outdoors gear is the loving work of his wife, Jian Hanli, who shoulders all the housework so Kuang can concentrate on his drawing. "We used to quarrel a lot about it. But seeing him wrapped in a quilt in winter, drawing, I began to understand his persistence," Jian says.

In 1997, after six years, Kuang and his family moved out of Beixin Hutong to a high-rise building. But he continued recording the stories of the hutong through his drawings.

In 2008 Kuang published his second album of pencil drawings, called Fading-Away Hutong, featuring 113 hutong in Beijing. Unlike his first album published in 2003, Kuang placed a photograph of the changed landscape of the hutong besides each drawing, revealing the dramatic contrast.

Shu Yi, former head of the National Museum of Modern Chinese Literature and son of renowned Chinese writer Lao She (1899-1966), has called Kuang's album a historic record.

Kuang says his albums are the best textbooks for later generations, presenting a history that goes beyond words.

"If only the Forbidden City survives, our children will wonder where ordinary people lived," he says

When asked about the new look of the hutong he used to draw, Kuang is silent for a while.

A view of Beijing's Dongsi Batiao Hutong in winter by Kuang.

Slowly, he says that while he is happy that hutong residents can now finally use central heating, have access to a private toilet and a kitchen in high-rise buildings, the loss of the beauty of old Beijing pains him.

He says the breakneck speed of development in Beijing leaves him with a great sense of urgency. If a hutong were to be pulled down before he can draw it, Kuang feels like he has failed the hutong.

"It's like a senior family member has died before I can draw his or her portrait," he says.

In 1996 Kuang realized that his pencils could not keep pace with the bulldozer and began to take photographs of every hutong so he could refer to them in his drawings. He now has more than 10,000 hutong photos and plans to devote the rest of his life to preserving them on paper.

"I wish I could do more to keep hutong alive," he adds wistfully.