From GROK
Mill glaze refers to a smooth, shiny, or polished surface that can form on wood during the milling or planing process, particularly with softwoods like cedar or pine. It occurs when the cutting blades of milling equipment compress and burnish the wood fibers, creating a hard, glossy layer. This layer can make the wood less absorbent, potentially causing issues with paint, stain, or sealant adhesion, as the glaze may prevent proper penetration or bonding.
Key Points:
- Cause: High-speed planing or milling generates heat, which, combined with the wood’s natural resins or sap, polishes the surface, closing the wood’s pores.
- Appearance: The wood looks glossy or slick, often feeling smoother than untreated wood.
- Impact: Mill glaze can lead to uneven staining, peeling paint, or poor adhesion of finishes, as it acts as a barrier to absorption.
- Solutions:
- Sanding: Lightly sanding the surface (e.g., with 80-120 grit sandpaper) removes the glaze and opens the wood’s pores for better finish adhesion.
- Cleaning: Using a wood cleaner or chemical stripper can also help.
- Weathering: Allowing the wood to weather naturally for a few weeks can break down the glaze, though this may not be practical for all projects.
- Context: Mill glaze is a common concern in woodworking, decking, or siding projects where proper finishing is critical for durability and aesthetics.
If you’re dealing with a specific project involving mill glaze, let me know, and I can provide more tailored advice or search for additional insights!
