Student record there observations as the "acid rain" interacts with their "stone column".

Student record there observations as the “acid rain” interacts with their “stone column”.

On April 24th NCPTT’s Materials Conservator Jason Church taught a lesson to two fifth grade classes (total of 56 students) from Northwestern State University Elementary Lab School. The students looked at how acid rain is produced and how pollution affects cultural materials.

As part of the lecture Church discussed experimental design and the scientific method. The students were given an assignment sheet and the problem of how acid rain would affect an outdoor sculpture. For this experiment each team of students (divided into pairs) were given a section of “stone column”. For this experiment the “stone column” was a section of chalk. To reinforce the experiment Church showed the students photographs of historic building columns in various states of weathering.

For the “Acid Rain” each team was given a small container of vinegar and a pipette. Each team had to hypothesis how many drop of acid rain it would take to see determination of their column and how many drops before their column disintegrated. Most of the teams pick 5-10 drops will cause total disintegration. After the teams have placed a few drops on their column, Church again discusses how weathering takes place over a long period of time.

Unknown to the students each class had one team whose “stone column” was coated in a polymer of Acryloid B-72. This polymer treatment coats the caulk giving it a slightly glosses appearance that was not noticed but any of the students. This polymer coating sealed the caulk not allowing the vinegar to react to the calcium carbonate of the caulk.

"Stone column" treated with a polymer.

“Stone column” treated with a polymer.

During the experiment the team with the coated “stone column” was slow to call the instructor over and finally asked; “after 30 drops our column does not look like everyone else’s column ”. At this prompt Church invited all students to inspect the treated column and hypotheses that made it different. Most guess were that it was a different material or that the vinegar was different. The lecture then turned to what is a polymer and how could it help slow weathering on cultural materials. Sealants, coatings, and consolidates for stone were discussed.

In addition to their experiment students looked at marble and limestone samples under the microscopes to compare both newly quarried stone and naturally weathered stone that was once part of an historic monument. Students also looked at how the stone is composed through thin section petrography.

Students compare weathered and unweathered marble samples under magnification.

Students compare weathered and unweathered marble samples under magnification.

 

 

 

 

 

 

Student looks at limestone in thin section.

Student looks at limestone in thin section.

Limestone in thin section.

Limestone in thin section.

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