It sounds like you might need more water too, I typically use 3L for about 300g of bark. at 500g I bet the bark sucked up all the water, so the naphtha is going to be difficult to seperate, add more water, at least 4L, or until you see your naphtha, and more base like house said
Expect nothing, Receive everything.
"Experiment and extrapolation is the only means the organic chemists (humans) currrently have - in contrast to "God" (and possibly R. B. Woodward). "
He alone sees truly who sees the Absolute the same in every creature...seeing the same Absolute everywhere, he does not harm himself or others. - The Bhagavad Gita
"The most beautiful thing we can experience, is the mysterious. The source of all true art and science."