Skip to main content Skip to footer

Hidden Treasure Behind the Milling Shop: Turning Spalted Wood

Moldy wood may look like trash, but woodturners know a treasure when they see one. In this blog post, Mary Tripoli turns a bag of moldy birch found on campus into stunning spalted bowls. 

Posted on December 21, 2023
by Mary Tripoli

North House staff cleans up the alley between the fish house and milling shop at the end of every season. Litter usually consists of detritus from outgoing interns, basket materials, unfinished carvings, etc. I was on campus a few weeks ago and Alex offered me two OLD garbage bags. One bag had split black ash; the other, moldy split rounds of birch. The ash was in decent shape and I’ll definitely use it for chair legs or rungs. The birch didn’t look great.

BUT I know a treasure when I see one!  Many woodworkers covet moldy wood. Fungi cause discoloration in many species of wood, which when worked (carved, planed, or turned) leaves dramatic lines and discoloration in the final piece.  

Here is a bowl that I turned with fresh green birch:

Now, here is birch that has been sitting in a plastic bag for 8 months.  And the resulting bowl!  

This process in wood is called spalting.  As you can imagine, different wood species will react differently to all the different fungi that exist in different regions of the world.  There are just a few things that I consider if I’m going to use spalted wood:  

1) The unique part of the piece I’m working on is the spalting. I would keep the form simple (if I were carving a spoon, I wouldn’t add a finial or add decorative chip carving). For a bowl, I would do a single fairly curved shape. I have been practicing round, slightly closed-rim forms lately.  

2) Wood that has spalted too much will just fall apart and not work at all for any project. Even though these logs feel quite stable, I will turn the bowls a little thicker than I normally would, to give a bit more strength.  

I’m very grateful for the windfall of turning blanks, and feel especially excited as they are special due to their wild designs and colors. That they came from a moldy bag that had been sitting forgotten is particularly satisfying!