What To Do When Paint Peels From Mill-Glazed Western Red Ceder/Redwood Siding

When paint peels from mill-glazed western red cedar and redwood siding, don't replace the siding. Learn how to return the wood to its original beauty.

If you're looking for the ultimate in durability, it doesn't get much better than western red cedar or redwood. Both are superior choices for decks, furniture and siding. The most common problem associated with these woods is mill glaze.

Mill glaze (also called planer's glaze) is not a finish added to the wood at the mill; it is a condition common to western red cedar and slightly less common to redwood, and it usually originates at the mill. Western red cedar and redwood contain water-soluble oils. These extractive oils can rise to the surface of the wood during the planing and drying processes. The dried oils coat the wood with a hard, varnish-type finish. The most common explanation for extractive oil rising to the surface at the mill is excessive heat caused by dull planer blades.

Professionals have been unable to verify with certainty that mill glaze occurs in flat-grained woods as a result of the planing and drying processes, yet the explanation persists. This conclusion, while controversial among lumber industry experts, is the most frequent explanation offered by the paint industry. Whatever the cause, the result is that primer and paint do not adhere well to woods afflicted with mill glaze.

When your painted cedar and redwood begins to show signs of peeling and cracking, you won't know whether mill glaze has caused the problem or whether some other cause is the culprit. While improper surface preparation and the presence of mill glaze are the most likely culprits, weathered wood--wood exposed to the sun's UV rays for more than two weeks before painting or finishing""also causes paint to adhere improperly. Skimpy coats of primer and paint are also responsible for peeling, chipping and cracking. In each case, the extractive oils rising to the surface are the root cause.

Rough surfaces require more primer and paint than flat, smooth wood surfaces, but the paint adheres better and lasts longer when applied to a rough surface, sometimes lasting twice as long. While smooth finishes decrease the life span of the final paint job, mill glaze decreases it further.

When your siding begins to display signs of peeling, chipping or cracking, you need to correct the problem as soon as possible to avoid blistering and weathering. If the problems are confined to small areas, you can usually prepare, prime and paint only the affected areas. If you pressure wash all of the siding, you should be able to match the finished color. Take the following steps to correct the situation:

1. Remove the paint and primer. You can sand the wood, pressure wash the wood, hand-scrape, or you can use a no-wax chemical stripper. Pressure washing may not remove all of the residue, but it will remove loosened paint and debris.

2. When using chemical strippers, take necessary precautions, wear protective clothing, and keep pets and children away.

3. If you use a chemical stripper, sand the wood after removal to create a rough surface.

4. Remove any residue, including sawdust, paint particles, dust and dead wood fiber.

5. Wash and rinse the wood. If the wood is stained from extractive bleeding, or if it is grey from weathering, wash with a special solution specially formulated for cedar and redwood. Ask your local building center for suggestions and help.

6. Allow the wood to dry thoroughly for a day or two.

7. Apply one coat of primer, and allow it to dry thoroughly--at least overnight.

8. If you notice staining after the first coat of primer dries, the tannins from the wood have risen and penetrated the primer. Add a second coat of primer, and allow the second coat of primer to dry thoroughly.

9. Apply one or two coats of latex or solid-body paint. Allow the first coat to dry completely before applying the second coat.

If mill glaze is absent or removed before the wood is finished, and if the wood is properly primed and painted, you will enjoy many carefree years from your western red cedar or redwood siding.

© High Speed Ventures 2011