There can be confusion between sapwood and heartwood that has not darkened in antique wood. As living trees mature they develop heartwood around the center. Pine heartwood has more resin than the surrounding sapwood. As mentioned in an earlier posting the heartwood darkens over time. In large antique pine beams it is common for this process to progress through out the entire piece. Occasionally however we find beams that still have yellow portions within the heart. These areas are called yellow heart. The picture has a board that was just surfaced showing areas that have changed color and areas that have not. The question is sometimes asked if these yellow sections are sapwood, but they are not. The sapwood is on the outside of the heart wood. If you look at the curvature of rings and the yellow has heartwood outside of it the yellow part is heartwood. Over time the light heartwood sections will darken and blend in.