The destiny of egg whites & egg yolks in cultural heritage preservation
The idea of eggs being mixed into lime mortar is a narrative in oral tradition we would hear from generations past. But as Spanish colonial churches, supposedly built with eggs as masonry material, continually deteriorated due to constant exposure to the elements and the natural aging process, the art and science of restoration started to attract more and more professionals and students interested in taking up heritage preservation as an actual academic course.
In the study of lime plaster restoration in the Philippines, the question of the mythical egg white’s presence in masonry at some point resurfaced, eventually calling for an investigation. It was then revealed through materials analysis that there was a very great possibility that egg whites were indeed mixed into the lime mortar used as the protective strata for stone churches.
Egg yolks, on the other hand, were said to be disposed of in nearby rivers.
Oral tradition has it that in the 1700s, churchgoing women were bothered by such a waste of food that it motivated them to formulate recipes— desserts in particular—to include egg yolks. And this, it is said, is the origin of well-known and well-loved classic desserts like yema, leche flan and tocino del cielo. The name “tocino del cielo,” in fact, originates from the 1300s, when nuns in the city of Jerez in Spain were given the leftover egg yolks after the egg whites were used to clarify wine.
The dessert’s name, “tocino,” which translates to “bacon,” came as a result of the bacon-y shade of brown the dessert acquired after the sugar had caramelized. And because they were made with holy nuns’ hands, the sweet, smooth and creamy dessert was named “tocino del cielo”—“bacon from heaven.” So, where egg yolks were concerned, the “myth” has physical evidence.
More scientific data is called for to determine what it was in egg whites that defined it as an inescapable “ingredient” in lime mortar, specifically for churches built during the Philippine colonial period. To name a few of them rumored to have egg content in their mortar are the Holy Rosary Church in Pampanga, Daraga Church in Albay, and Baclayon Church in Bohol.
Professor Ricardo Trota Jose, who has authored several extensive discourses on churches, notes that as early as 1780, duck egg whites were believed to be added into the mortar mix to render it more binding. But he does raise some questions: “Were duck eggs preferred to those of chickens? How many fowls were needed to produce the quantities needed?”
Various research abstracts state that, for one, duck eggs are bigger than chicken eggs; duck eggs have less water content than chicken eggs and therefore have less-runny whites; duck eggs contain more fat—an average of 9.6 grams versus 5 grams; and duck eggs also contain more protein, the binding agent necessary for lime plaster adhesion. Still and all, it does not contribute to the presence of egg whites in mortar… yet.
Lime plaster is termed “palitada,” a plaster made from broken limestone pieces (or in some areas, seashells), and burnt to a certain degree for a scheduled time. After it is “cooked” (in Italian, “calce viva”) it was soaked in water (slaked) and kept moist and stored in a shady area for a minimum of three months before using.
In other countries like Italy, lime is considered at its best after 10 years of slaking. The “cooked” and slaked lime, technically known as hydraulic lime, is then mixed with river sand, which has no salt content. If sea sand is used, it is soaked in clean water—sometimes for a year—or left under the rain, or rinsed many times over to rid the sand of salt, which is a destructive and corrosive element to lime plaster and stone.
It is at this point that egg whites are said to be added to the mortar. To date, experiments have been conducted on the veracity that the protein in egg white does increase the durability of lime plaster and enhances a faster drying period. Before he left to finish his PhD in Analytical Chemistry with a major in the analysis of cultural heritage at the University of Tartu, Estonia, Jan-Michael Cayme attempted experiments to determine the presence of those certain proteins.
“A few years ago, we made model mortars where we intentionally added different ratios of egg whites with lime to test whether the basic chemistry techniques we are familiar with can detect proteins in lime mortars. Indeed, we detected them after the extraction, but we are not satisfied with that yet.”
Future experiments with more advanced chemistry equipment and techniques will seek to find “trace amounts of egg white proteins in real-life historical lime mortars,” says Cayme.
While other countries, like India, have had conclusive lime experiments, the Philippines still has to examine the possible varieties of limestone content with different material compositions, given that we are a country of 7,100 islands. The location of the stone contributes to its properties.
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In the meantime, it remains imperative that eggless lime plaster applied on stone surfaces, especially, remain pure and devoid of any added percentage of modern cement, which some restorers follow to guarantee a faster drying time. Lime mortars set more slowly, but the addition of cement compromises the lime mortar’s flexibility, making it less sympathetic to masonry. The addition of cement can stiffen lime mortar and trap moisture within the stone, leading to even more destructive results, like the solid chipping off of the mortar from the stone substrate.
So, as the egg whites’ future place in cultural heritage still remains uncertain, the egg yolks’ presence in gastronomic heritage of sinful desserts basks in festive occasions. In Pampanga, celebrated pastry chef Atching Lilian Borromeo’s heirloom recipes that utilize egg yolks galore are popularized in several of her cookbooks and YouTube cooking demos that eschew diets and support a sweet tooth. She is even featured in the ultimate global foodie guide, Gastro Obscura. A visit to Pampanga is not complete without dropping by Atching’s restaurant and loading one’s vehicle with sucrose-raising pasalubongs.
Despite historical records attesting to the use of egg whites to form a kind of mortar called “argamasa,” there is, so far, no tangible laboratory proof of the existence of eggs in historical masonry. It would be very interesting to reach a eureka moment when solid evidence proving egg white content in lime mortar is conclusive.
Contrary to widespread beliefs that cultural heritage is exclusively for elitist scholars, think again. What you may be having for breakfast could be a significant and historical heritage-preservation material, scrambled or sunny side up.