Furniture dealers often talk of "patina" a gradual darkening of the wood over the passage of time. I don't think this is a natural ageing process but more likely the gradual accumulation of dirt trapped on the surface.
In your restoration project you fail to mention what type of cabinet - kitchen cabinet etc - and neither do you say what the existing finish is.
It may be French Polish - Varnish - Wax - Oil - nothing.
Cleaning methods are Sandpaper - Chemical Strippers - Caustic Soda which will all remove the finish completely and require major restoration. For light dirt you can seek out some 0000 grade wire-wool - very, very fine - and gently clean the top surface with gentle rubbing and a lubricant like white spirit. Sugarsoap would be a more gentle first approach and you may do best to begin with the gentle touch and progress to the more severe if required.
Traditional Hardware stores sell specialist wood restoring products for a price - these may be worth investigating.
Good luck...
Peccavi, May 2010
