Expert: Greg Scholl - 7/13/2009

Question
Hello Greg,
I have a problem with the exterior face of oak windows. Unwisely we applied a clear lacquer which led to some UV damage and ingress of water and some staining. We soon had to get the windows sanded and applied a sadolin varnish with a stain. Unfortunately the finish is not great and also the stain is breaking down particularly at the base of the windows (ie drip details). This was completed only 1 year ago. We realise these windows will require ongoing maintenance but surely not every year. Someone mentioned we should not sand down but use a sharp edge tool (similar to a planer) to remove the existing varnish layers and then re-apply with a good quality varnish with a darker stain. Can you offer any advice.
Many thanks. Jimmy

Answer
Hi Jimmy, I believe they were referring to a scraper, like a cabinet scraper which is basically a small rectangular piece of tool steel that gets sharpened to allow scraping. In my opinion the best course of action is a chemical stripper, though to be sure you get ALL the old finish off, down to bare wood. You'll also need to apply at least 3-4 coats of any exterior finish over an exterior stain, but typically varnishes and the like over a stain, and on Oak, won't last much more than you're experiencing because of the nature of the materials. Oak is very porous, and one needs to be thorough about encapsulating the wood and treating the end grain ,too, and of course since the trim is already installed, you can't get to some of it.....but the water can. I think I would steer you towards a penetrating oil finish, instead of a surface finish like Varnish, although I am totally unsure about what products you have access to there....here we have something like the Flood-CWF Oil or CWF Hardwoods, or Cabots, or Sikkens Cetol penetrating finishes, used for Decks, Outdoor furniture,Marine wood, trim, etc. They penetrate the wood and harden from within, instead of sitting on top of the wood, and they resist flaking or chipping because of that....they also are available with color in them which is a better system than stain and a topcoat in an exterior situation. Thesa will take maintenance too, but because they're penetrating finishes, it's a much easier job. Hope that helps a little- Post back if need be- Regards- Greg

http://www.nam.sikkens.com/product.cfm?product_id=3&product_category=exterior

http://www.floodco.com/index.jsp

http://www.cabotstain.com/products/product-type/Staining%20Products.html