On a recent visit to Jane Sanders’ EnerPHit Brooklyn brownstone retrofit, Floris took the opportunity to demonstrate the basics of Karsten tube testing. These tests are one of the ways to ensure the brick is good and ready for a high performance retrofit. Passing the test proves the brick is not too absorptive from wetting by precipitation. Conveniently, the building next door presented a great learning example of the evidence of freeze-thaw damage on masonry. For those interested in high performance masonry retrofits, learning to test brick with Karsten tubes is an essential part of the professional’s tool kit.