let it cool before you put it in your tank (sounds obvious but you never know). I usually stick mine in a 5g bucket of water until the next day. Be prepared to weigh it down in case it doesn't sink with large rocks or something.
i have a mopani wood and even after letting it stay in a tub in water and boiling for hours it still releases the tannins.. the look your tank gets is nice maybe for the first 2-3 days after a water change but then it can get pretty dark and your tank light will seem dull.. just do water changes and try purigen