Non Valk-House mold-where to begin?

[Zep]

I own a 104 year old home.  Two story stucco.  Plaster walls.  Beautiful home.  Northeast corner house.  Second story.  From the top of the wallboard up 18 inches  and about three feet either way there is mold coming through the wallpaper.  Wall feels solid.  No other mold elsewhere I can find.  Anybody know first steps to take, and, or what source I can go to to learn about and treat this?  Thanks.

Zep

[laserpat]

Typically mold is caused by a water leak possibly roof, walls, windows, plumbing so the frist step is to find and fix the cause. then remove the moldy area. Bleach kills most molds but if the mold is inside the wall you will need to open it up

[Kingbee]

Considering the age of your home, and your geographic location, the mold could also be caused by condensation due to poor insulation.  Some wallpaper adhesives can be a breeding ground for mold and mildew if exposed to moisture, which could actually be activated by moisture on the room side of the paper, and then growing through the paper and appearing in the room.  Is this problem near a corner? Is this a room that's fully heated? Is your humidity too high for a given outside temperature? Got enough air circulation in this room?  Just some things to think about.

Yeah, I was a painting contractor for 36 years..............

[Blackduck KS]

Try using clorox bleach on it use a sponage or rag, let it set after dried for a month or so see if it returns but it shouldn`t if there is no leak anywhere had this problem in daughters basement do to  damp mioster humidifyer helps to prevent it also.