The Fascinating Transformation of Walnut Heartwood: A Deep Dive into Nature's Color Magic
Hey there, friends of Hazel Oak Farms! It's Ethan here, owner of Hazel Oak Farms in Eastern Iowa. If you've been following us on Instagram (@hazeloakfarms), you might have caught my recent post showcasing some freshly sawn walnut slabs straight off of our sawmill. The response was amazing—folks were captivated by how the wood seems to "come alive" with color right before their eyes. Today, I wanted to expand on that in this blog post, sharing the science, beauty, and practical side of walnut heartwood oxidation. It's one of those natural wonders that makes working with local lumber so rewarding.
The Fresh Cut: What You See Right Off the Saw
When we mill a black walnut log, the heartwood—the dense, inner core of the tree—doesn't immediately show off its signature deep tones. Instead, it's often a lighter shade, sometimes with a subtle greenish or pale brown hue. This is the wood in its raw, unexposed state, full of potential but not yet transformed. In my Instagram post, I shared a close-up of these fresh slabs, still damp from the cut, to highlight that initial appearance. This lighter color is common in freshly sawn black walnut. The sapwood (the outer layer) might even show bluish stains due to immediate reactions with moisture and air.
The Oxidation Process: Turning Brownish-Purple Over Time
Here's where the magic happens: exposure to air triggers oxidation, a natural chemical reaction where enzymes in the wood (polyphenol oxidase - PPO) interact with oxygen. When the walnut is cut, this enzyme is exposed to oxygen and catalyzes the oxidation of phenolic compounds to quinones. Within hours, that pale heartwood starts darkening, evolving into a rich, deep dark brownish-purple hue. It's not just a subtle shift—it's dramatic and beautiful, often revealing streaks of purple that make each slab unique. Why purple, you ask? In some cases, it's influenced by the tree's growing conditions, like mineral-rich soil or proximity to water sources, which can infuse the wood with those distinctive tones. Sunlight and further exposure can refine or even fade these colors over time. If you've ever seen a piece of aged walnut lighten slightly in a dim room or bleach under direct sun, that's the ongoing dance of these elements. In our Instagram photos, you can see this progression in action. We captured the slabs right after sawing, showing how the color intensifies without any stains or finishes—just pure nature at work.
Why This Matters for Our Handcrafted Furniture
At Hazel Oak Farms, we turn these transformed walnut slabs into one-of-a-kind pieces like live-edge tables, desks, clocks, and countertops. The oxidized heartwood's depth adds character that's impossible to replicate with stains or dyes. Whether it's a waterfall coffee table or a simple side table, that brownish-purple glow brings warmth and elegance to any home.We've been busy milling walnut lately, as you might have seen in our social posts—everything from book-matched sets to massive logs yielding 10-12' slabs. Our custom builds highlight these natural changes, and we love working with clients to select the perfect slab for their project.
Nature's Gift in Every Slab
We hope you enjoyed learning about this amazing natural process, and maybe it makes you appreciate wood even more. If you haven't checked out the Instagram post yet, head over to @hazeloakfarms and let me know what you think in the comments! Interested in your own walnut piece? Browse our collections on the site or reach out for a custom quote. We are always sawing, building, and shipping nationwide. Thanks for reading, and stay tuned for more behind-the-scenes from the farm.
Until next time,
Ethan Morford
Hazel Oak Farms
Ethan Morford
Hazel Oak Farms
P.S. Here is a video of us cutting some other walnut logs for you to see.
