Replies

1. 
   yotonyb | Oct 13, 2008 07:40pm | #1

   The sap wood will not change color.  Sap wood lacks the tannin necessary to react with the ammonia that causes the color change.

   That said, if there were a way you could introduce tannin into the sap wood, perhaps you could mimic the natural reaction of the tannin-rich heartwood...and there is!  Check with a local brew shop or winemaking supplier.  They sell powdered tannin (used as an additive in wine) and you can make a solution to paint on the sap wood prior to fuming. 

   This past spring I tried this technique on some test pieces.  It worked, but the color shift wasn't nearly as pronounced as on the heartwood.  I used some powdered tannin leftover from winemaking season last fall, and I wouldn't exactly call what I did a controlled experiment.  But the sap wood washed with the tannin solution did change color after fuming relative to the untreated sap wood.

   The more traditional system is to use a combination of stains and dyes to color the sap woods.  But the sapwood will absorb stains and dyes differently than the heartwood making the the difference between the two just as pronounced if you simply start slapping on different finishes. 

   These are definitely the kind of experiments with test pieces necessary to achieve predictable results.  It's not something I'd try on your final piece for the very first time.

   Some very early projects (two table tops come to mind) feature very pronounce sapwood stripes as a result of my poor finishing background.  Since that time I've worked around the sap wood for this very reason.  None-the-less, learning to tone the sapwood to produce the same finish as the heartwood is a tremendous finishing skill, one that can help you overcome an obstacle that stops others (like me...) and one that can stretch your material and utilize more of what you have rather than working around a great resource.

   tony b.