First, Wait a Quarter of a Century

The profession of restoration has a very strict code of ethics that reads somewhat like the Hippocratic Oath:

1) First, do no harm.
2) Every step you take should be reversible.
3) Use the original material whenever possible.
4) Document your work thoroughly with before and after photos.

A friend told me today that construction of the church in Alamos was overseen by the Spanish crown, and the construction statutes of the era called for lime to be slaked for at least 25 years.

During the Roman Empire lime for construction was, by law, slaked for 3 years. When I worked on the frescos at St. Mary's College with Mark Balma, we used 200 year old lime from the Vatican lime pits to make the "bianco san giovanni," the white pigment. European builders and fresco painters in general have long understood that the oldest lime is the best, so they used to pass their lime pits from one generation to the next.

Interestingly, the Maya invented a shortcut. They added tree mucilage to the lime. The sugar content accelerated the slaking process, so the lime was ready for use in 2 weeks, rather than 2 years.

The old building tradition in Alamos called for adding the mucilage of a tree from the same family the Maya used.