Fehling's solution is a staining formula I used in enhancing tree ring identification. It is a product of Forest Products Laboratory, Madison, Wisconsin. It appeared in an article in 1962 entitled "Color Tests for Differentianting Heartwood and Sapwood in certain softwood tree species. USDA Forest Service, Report No. 2246." Fehling's Solution is 3.5g copper sulfate, 17.3g potassium sodium tartrate, 6.0g sodium hydroxide with 100.0 ml water. Brush on after sanding sample and leave dry overnight.

A microscope mounted to a table with a movable top provided us with the technique to identify tree rings and measure their widths from tree cross sections. Data is automatically transferred to a computer file.

Cross section of ponderosa pine showing growth release in response to thinning. Picture is credited to W.K. Olsen, 1998 Advanced Forestry. http://www.advancedforestry.com