A RECENT exhibit at the Saint Paul Metropolitan Church's Museo de San Pablo sparked a question on the preservation of Vigan City's Heritage Village. Should the ''skin'' of old churches be used for the remodeling of the 19th century walls of old houses in Vigan? ''Palitada'' is the term used for the lime mixture applied on walls of old Philippine churches. Back when there was no cement, apog or lime was mixed with sand (as salt-free as possible) to form a binding mixture in a process called argamasa.

The roving exhibit, ''Palitada: The Skin of the Church,'' by the Ayala Museum Foundation, with the help of Fundacion Santiago, Tawid ti Ilocos Foundation and Grupo Farola, brings to fore this old masonic art. To make the palitada more durable, egg white, molasses and plants were added to the argamasa. Plants included the puso-puso or batikuling (Litsea glutinosa), its leaves chopped and soaked in water before they are added to the mixture to make the palitada waterproof. The extensive use of egg white and egg shells made it necessary to use the yolk as well, that is why we still have egg-based desserts like pan de Nicolas, yema, tocino del cielo and leche flan.

In areas without lime, churches are made of piedra bituca (literally, stone intestines) produced from gravel, coral and stone. The San Agustin Church in Intramuros, Manila, is made of adobe. Other churches are made of adobe, volcanic stone and coral stone or piedra de Visayas.

Bricks

Monsignor Thaddeus Mercado of the Saint Paul Metropolitan Church said most churches in the Ilocos region are made of ladrillos or bricks.

He said kilns in Pagburnayan village in Vigan City used to bake these bricks for the churches and houses in Vigan and neighboring towns. Included in the exhibit were ladrillos from the churches of Narvacan, Santa Maria, Bantay and San Ildefonso towns.

When there was no more use for ladrillos, the kilns were used to churn out jars and figurines.

The palitada was applied over the church walls as ''the skin of the churches.'' Mercado said the traditional palitada should be revived for the finishing of the Vigan houses to make them more authentic and, more importantly, to keep the heritage site status of Vigan's Heritage Village.

''Now almost all use cement instead. The Unesco (United Nations Educational, Scientific and Cultural Organization), which granted Vigan the status of a heritage site in 1999, is very strict on authenticity. We could be delisted if we don't follow the palitada on our houses,'' he said.

Heritage

The Unesco chose Vigan as a heritage site since it represents a unique fusion of Asian building design and construction with European colonial architecture and planning. Vigan, it said, is an exceptionally intact and well-preserved example of a Spanish trading town in East and Southeast Asia.

The Palitada exhibit, incidentally, included the unsightly errors made in preserving Philippine churches. These included painted cement to make them look like simulated wood, peek-a-boo bricks, simulated coral stone over real coral stones, stripped palitada to expose the bricks and laying bricks over stone tiles.

Vigan Mayor Eva Marie Singson-Medina said the possibility of a Unesco delisting is the least of their worries.

She said the National Historical Institute (NHI), in its guidelines, gave a formula of lime and cement for the plaster in restoring the walls of the Vigan houses.

''We are abiding by the NHI guidelines,'' Medina said. It was former first lady Imelda Marcos who ordered the whitewashing of the Vigan houses in the 1970s, giving them a ghostly but unnatural sheen.

''I still believe that the original Vigan houses were colorful,'' Medina said.