word of caution, something I just learned

[rayknight]

Had a pair of cherry Federal sidetables, ebony  corner edging and fan inlays, was real proud of the matched pair of tables. the top surface was urethane finished. Used  them beside my bed for several months. Nothing on the table except a small battery powered alarm clock with lit time display.  A  week ago, found a black stain material on the top surface, the stain appeared to be on the top, not in it. you could feel the edge with your fingernail. Talking to all family members and the cleaning lady, no one seemed to have an idea what it was.  I tested a range of solvents, none of which seemed to touch it.  I  then took a cabinet scraper and began carefully scraping it  off the top of this finish (or so I thought). As I scraped it carefully it became obvious it actually extended through the urethane finish and even into the wood.  What the bejeezus was it. Closer inspection of the clock, showed AAA batteries in the   bottom of the clock, with a ribbon, that serves to help remove the batteries. The ribbon was protruding from the bottom of the clock, it did not appear to have any substance on it. the shape of the protrudingd ribbon closely mirrored the  shape of the black stain. But removing the batteries showed a thin rim of breakdown on the tip of one of the batteries. A friend   dropped by and said  he was aware  batteries can do this.was there local microcircuits burning into the urethan or w as it  a  chemical thing. 
     Have any of you had a similar problem.  I will never a again place a battery operated device on a wood finish, without a  pad. I will be able to refinish the spot, but it will be a slight divot  from the scraping and a small bit of the black stain will remain in the wood. 

Ray Knight

[fredhargis]

Bummer! I haven't had that happen or read of similar problems. (Many) Years ago i did have clock leave 4 black dots on a factory nightstand. Turns out back then they had plasticizers in the rubber feet to keep the compound soft. Those same plasticizers could also soften and discolor finishes.

[jteneyck]

There are a lot of materials that can damage a finish.  The only sure-fire way I know to protect a tabletop is to put a piece of glass on top.  Not too attractive, however.

John