Better Safe Than Sorry
The Importance of Cleaning Tests
When done right, cleaning can greatly improve the appearance of a historic building. As a result, many restoration projects focus on cleaning. While cleaning may seem like a rather straightforward process, when done wrong it can cause irreversible damage.
Therefore, testing and mock-ups must be performed before any large-scale cleaning is undertaken to determine the most gentle, yet most effective, cleaning product(s) for the project - every time.
After years of experience, lessons have been learned, many of them the hard way.
Testing is helpful in establishing a level of cleanliness that meets the client’s expectations while respecting the age of the building.
It is difficult to predict how a substrate or soiling condition will react to cleaning agents. Even if a product has been successfully used on the same substrate with similar soiling for another project does not guarantee that it will work this time.
Not all soiling is the same. Different soiling conditions may require different products. In addition, different substrates may require different cleaners for the same soiling condition. The before and after images below perfectly exemplify that not all cleaners work the same on all materials. While the goal is to find a single product that works well on each substrate, it cannot always be achieved.
Companies can change the formula of cleaning agents without notice. A product that was tested a year ago may not be the same product that is purchased today. This is especially true for paint strippers that have undergone formula changes in recent years due to stricter environmental and safety regulations.
A product’s effectiveness can vary greatly depending upon environmental conditions. Temperature and humidity can have a significant effect on the performance of a cleaner or paint stripper. Products that were effective when tested during cooler temperatures may be too harsh when used in warmer weather. Conversely, products that worked well when tested in warmer temperatures may not work as well in colder weather.
Hence, no matter the reputation of a cleaning product or the experience of the conservator or contractor, cleaning tests and mock-ups should be performed every time a project is undertaken. After all, it is better to be safe than sorry!
Figure 1: Before a cleaning test is performed on brick, limestone, and granite.
Figure 2: Brick, limestone, and granite after the cleaning test.