Since the weather outside has been nice, I decided to open some windows and air out the house. The bottoms of the window frames in the kitchen, bedrooms and the bottom wood frame of my french doors all have black moldy looking mildew stuff on them. I used Tilex to clean it off then read that it wasn't supposed to be used on wood so I wiped it off well with paper towel. What is this gunk and how do I keep it from coming back? Thanks, kjh9835

 

You were correct in thinking it is mold / mildew. It is likely, however, that it is nothing to worry about, healthwise. Mold spores are present in every square inch of air we breath, and they will only grow in places where the climate is just right- in this case, the bottom of your window sills and doors.

Most forms of mold can only grow in places where the relative humidity is 60% or greater. If sweat forms on your windows, that means the humidity there has reached 100%, and condensation has begun to form. (The pemperature in those locations is so low, it has reached the dew point).

The best thing for you to do is likely what you have already done- clean it off. The best thing to use is a soapy detergent that will not harm your woodwork. TSP is a product sold in most hardware stores that works well for this sort of thing. Detergents usually leave a microscopic slick film behind, which is also beneficial, because slick surfaces usually resist mold growth.

The mold likely formed because of the cold weather outside, and warm moist temperatures inside. Keeping your woodwork polished with furniture polish or wood oil will help, or if the finish on the woodwork is worn thin, another coat of varnish or polyurethane might help those surfaces remain mold free next time. At the least, they will wipe up easier in the future.

Best wishes!

 

This same subject was discussed a few weeks ago- you can read it at: http://forum.doityourself.com/showthread.php?t=197616

 

Thanks for your time to reply. Have a great day!