Mohammed Fathi worked his brush gently over an icon of Virgin Mary and baby Jesus, removing soot from its surface inside a church gutted in an attack by Islamist militants this month.
"It takes a lot of careful work to do that," Fathi said. "We have to do a lot of tests with chemicals to try to restore the icon to its original condition."
The 26-year-old is one of a vast group of mostly Muslim craftsmen tasked with restoring St Mary's Church in the Cairo suburb of Imbaba after militants set it on fire on 7 May.
Egypt's military rulers have ordered its restoration at a time when tensions between Christians, who account for about 10 percent of Egypt's population, and Muslims are on the rise.
Attacks have triggered protests and pose a challenge for Egypt's new rulers, under pressure to impose security while seeking to avoid the tough tactics against Islamists used by deposed President Hosni Mubarak.
The ground floor of the four-storey church was gutted in the fire, destroying 10 out of 27 old icons beyond repair.
On Wednesday, a team of mostly Muslim restorers — working for one of Egypt's biggest construction firms known as The Arab Contractors — huddled in one corner, using special chemicals, paint and brushes to rescue the remaining paintings.
"My job is to restore historic art pieces, be they Muslim, Coptic or Jewish," Fathi said.
Malak Gerges, a 56-year-old church driver who was inside the church at the time of the attack, recalled how bearded Islamists led a group of young men into St Mary's, opened fire on icons and set the building ablaze.
He said he and his younger brother Saleh tried to hide in the corridor behind the altar but the militants found them.
"They dragged me out and threatened and abused me," Gerges told Reuters.
He said he did not know what happened to Saleh, an attendant who helped look after the church, until rescue workers found his burned corpse inside the church. According to an investigation report, there was a wound on Saleh's throat, he said.
Abdel-Aziz Mohammed, working on another icon, said he was angry at the people who burned the church. "I felt this was an act of vandalism," he said. "Islam does not distinguish between church and mosque — both are houses of God."
The 7 May attack caused an outcry in a country grappling with growing crime and lawlessness after an uprising forced Mubarak from power in February.
Egypt's ruling military council has vowed to punish those behind sectarian violence and promised to protect Christians by tightening security around places of worship.
Sectarian tension grew during Mubarak's three decades in office and accelerated in the chaos that followed his overthrow. Many Christians say the military-led government is being too soft on the Islamist radicals who whip up inter-faith hatred.
The governorate of Giza, where Imbaba is located, has pledged to pay for restoration of St Mary's church, expected to cost around 6 million Egyptian pounds (US$1 million).
For now, workers are busy plastering and painting its walls and sweeping out the dust, pushing to finish their work as quickly as possible.
"This work would normally require up to three months. We are doing it in 21 days," Ibrahim Mahlab, chief executive of The Arab Contractors, said while inspecting the work. "We want to show that no intruder can create a rift between Muslims and Christians."