What is mill glaze on new cedar siding and how do I remove it before priming and painting on a New Brunswick home?

Mill glaze is a shiny, hard surface layer created during the lumber milling process when high-speed planer blades compress and burnish the wood fibers. This glossy surface prevents primer and paint from properly adhering to new cedar siding, leading to peeling and adhesion failure within 1-2 years if not properly removed before painting.

Mill glaze forms when cedar boards pass through industrial planers at high speed. The friction and pressure from the metal blades compress the wood fibers and natural oils to create a glass-like surface that looks smooth and appealing but is terrible for paint adhesion. Fresh cedar siding straight from the lumber yard almost always has mill glaze — it's that unnaturally smooth, slightly shiny appearance that feels slick to the touch.

In New Brunswick's climate, mill glaze becomes an even bigger problem because our freeze-thaw cycles will quickly lift any paint that isn't properly bonded to the wood surface. The combination of Maritime humidity, temperature swings, and UV exposure means that paint applied over mill glaze typically starts peeling within the first winter.

Removing mill glaze requires mechanical abrasion — you need to physically roughen the surface to expose fresh wood fibers that primer can penetrate and bond with. For cedar siding, use 80-100 grit sandpaper and sand with the grain direction, not across it. A palm sander speeds up the process significantly compared to hand sanding. You'll know you've removed the mill glaze when the surface loses its shine and feels noticeably rougher, with visible wood grain texture.

After sanding, clean all dust off the siding with a tack cloth or compressed air before priming. Cedar contains natural oils that can also interfere with paint adhesion, so use a high-quality oil-based or shellac-based primer specifically designed for cedar and other resinous woods. In New Brunswick, popular choices include Zinsser Cover Stain or Benjamin Moore Fresh Start primer.

Timing is critical in our Maritime climate — only remove mill glaze and prime during dry weather conditions between mid-May and mid-October. The wood must be completely dry (below 15% moisture content) before sanding, and you need at least 24-48 hours of dry weather after priming before applying your finish coats. Never sand cedar siding in the spring when it's still absorbing moisture from snowmelt and rain.

For a full house of new cedar siding, mill glaze removal is definitely a job for professionals. The amount of sanding required is substantial, and achieving consistent surface preparation across hundreds of square feet of siding requires experience and proper equipment. Professional painters have pneumatic sanders and dust collection systems that make this work much more efficient and cleaner than DIY methods.

Find local painting contractors experienced with cedar siding preparation through the New Brunswick Construction Network directory — proper mill glaze removal is essential for a long-lasting paint job on your new cedar siding.