Rot Doctor


Subject: Wet Window Frame
Date: Sat, 22 Sep 2001

Dr. Rot, I hope you can help me. I have three windows in my bathroom that are solid pine. The pine was treated with your standard stain and standard varnish almost 10 years ago. I noticed this past year the bottom of the window frame and the adjoining sill were starting to turn black. It appears that the steam from the shower was hitting the cold windows in the winter (we live in Chicago), condensing and the water was sitting on the window sill. I have stripped and sanded the lower part of the window frame and the sill. There is a lot of black still in the grain, but what bothers me is the bottom of the window frame is wet. I have left the windows open for three or four days, but the wood is still wet and soft. I wanted to get the black out, dry the wood, re-stain and varnish. Is that possible?

Thank you for your help,



The blackness you are seeing is the residue from bacterial degradation of the wood. It’s basically wood rot, but with bacteria rather than fungi being the destructive agents.

What you should do here is allow the stripped wood to become reasonably dry (you can often enhance this process by propping a hair dryer in place and putting it on low heat/high fan)). Drying can take some time, but you won’t ever be able to proceed with treatment/refinishing until it dries.

Once reasonably dry, go to a hardware store and buy some wood bleach, and bleach the blackness out of the wood. Sand smooth afterwards, and then stain with a wipe-off type stain. Allow this to become thoroughly dry. Then come back and treat all stained wood with our CPES (Clear Penetrating Epoxy Sealer). Give that a day or longer to cure, and then re-finish with whatever clear coating you are using.

A word here about the CPES treatment. What is happening to your sill is that the condensed water is seeping under the finish and getting into the wood. CPES protects wood against degradation by either bacteria or fungi, and so to the extent that you can get the wood stripped clean, including the seams and junction edges, and treat it with CPES before finishing you will be giving your sill great protection against this sort of thing happening again.

You can apply your clear finish directly on top of the CPES-treated stained finish.

And come on back if you have additional questions.