It could be that the older stain has faded over time. Even though most
stains contain finely ground pigment, they can also contain a dye that
may fade in sunlight. We've noticed this on our floors when we rolled
back a carpet.
You might dilute the stain with solvent until you get close to the tone
valus of the old work. The eye conpensates for small differences.
Joel Jacobson
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