Vinegar and Pennies as Wood Stain

I thought this was such a cool idea and a great green way to get color into your wood without all of the chemicals.   We put the "handful" of pennies into vinegar and let it sit for one week.  As you can see from the pictures below this did not work at all.  I am not sure what a "handful" of pennies meant but maybe my "handful" was not big enough.  I have a suspicion that the stains with berries and coffee would work a lot better and will try those out next, but as for the vinegar and pennies,  it did not work at all.

RESULTS
PINS DOWN
**-ease
*-effectiveness
**-cost
*-time
*-practical