Hello! My name is Silvia Lob, I am an intern at the NCPTT, and I am working on a project to evaluate commercially available products marketed to prevent efflorescence on masonry. I have a masters degree in physical chemistry from the University Pierre and Marie Curie in Paris, and I have always had an interest in cultural heritage. I worked in France prior to moving here to the NCPTT to conduct research focused in historic building preservation.

This project aims to test a variety of commercially available products marketed to prevent efflorescence, with aim of determining which products perform the best without causing damage to the substrate Commercially available products were selected for testing because the goal of this research is for the results to be publically available and applicable not only for National Park Service staff charged with caring for cultural heritage, but also private citizens.

The 5 products tested are:

-Cathedral Stone Products (CSP) Guardian Water Repellent: a stable, VOC compliant, water based silane/siloxane blend water repellent. It is designed to treat bricks from efflorescence, with a good stability and a long term durability.

-Siloxa-Tek 8505: a nanotechnology driven, high performance stain resistant water, salt and oil repellent, designed to protect against water-soluble deleterious materials oily substances and freeze/thaw cycles. Its interaction with the substrate should create a shield that aide in a dramatic reduction of chloride and water absorption.

-Dry Treat Meta Crème: a sealing technology for protecting natural stone and masonry, designed to provide protection against efflorescence.

-Efflock TT, Topical Efflorescence Treatment: a liquid topical treatment for pre-existing concrete and masonry surfaces designed to eliminate both primary and secondary efflorescence.

-Aqua Mix Eff-Ex: a non-acid (pH 7.4), heavy-duty cleaner designed to remove and inhibit efflorescence.

The experimental design of the project was begun by Lucy Midelfort. I began working on this project in the realization phase along with Elle Farias, a fellow intern at NCPTT. We are each working on separate approaches to a similar project:

-The first project is a salt efflorescence study on brick and mortar wall assemblies subjected to simulated ground water and driving rain.

-The second project is a salt efflorescence study on single bricks subjected to artificial Q-UV weathering.

Elle and I built the walls together. You can read more about our test wall building process on Elle’s blogpost “Building Masonry Test Walls”. Constructing Historic Masonry Test Walls

Silvia (me!) leveling the bricks

Elle (my new bestie!) applying mortar

construction of the 7th and last wall

In the next phase I will focus on applications of treatments and recreating efflorescence on the seven test walls. The salt solution was determined in the design development phase by Lucy Midelfort and was based on correspondence with Hilde de Clercq, from the Institut Royal du Patrimoine Artistique in Brussels, who specializes in salts and their interaction with historic buildings. The salt solution will be mixed then poured into the plastic tubs within which the walls are standing. This process will allow the salts to migrate through the brick walls and then to effloresce at the surface.

N.B.: the walls have been painted with a white waterproof paint (Laxon XP, waterproofing masonry coating, extra white), on the backside and both left and right sides, so that the moisture containing the salts cannot evaporate from those surfaces. Our goal is to test the front side of the walls only. And to do so, we need to prevent efflorescence from forming anywhere else.

control test wall with a clean front side

control test wall with sides painted in white






The salts mixture that will be used in this experiment is a sodium chloride (NaCl) + sodium sulfate (Na2SO4) solution at an equimolar concentration of 1.1mol/kg. This means, for every  1L of water there is 32,14g of NaCl and 78,12g of Na2SO4. The plastic tubs we built our walls in, have a capacity of 60L. 15L of the sodium chloride and sodium sulfate solution will be added below each wall in order to fill the tubs to approximately half capacity.

Now, let’s watch the moisture rise and see y’all in the next blogpost!


National Center for Preservation Technology and Training
645 University Parkway
Natchitoches, LA 71457

Email: ncptt[at]nps.gov
Phone: (318) 356-7444
Fax: (318) 356-9119