Preservationists believe the Montanez Adobe, built near the Mission San Juan Capistrano in 1794, once had a straw roof and floors made out of mud, straw, water and cow's blood.
So this Saturday, at 10:30 a.m., the public is invited to watch preservationists use the Spanish colonial technique to lay a new adobe dirt floor, curator David Whittington said.
The mud floor will take 30 to 60 days to dry. Then a second layer of sand, finely chopped straw, water, horse manure and cow's blood will be slathered on top of the dirt floor to form a surface so hard it could be waxed, Whittington said.
The city's Cultural Heritage Commission next month will be asked to approve the use of the process in the second stage of the project.
"Any time you talk about blood and guts, it always gets you in trouble," Whittington said. "But there is evidence of blood in the plaster. It was used to harden and make plaster."
Information: (714) 488-8941.