Yes the carbon is great or at least it was for SWIM, the ratio was 3 part FB to 1 part carbon. SWIM used naphtha for this but had heard reports of others using 99%IPA. SWIM noticed a small loss in product but it seemed to be impurities only. The carbon type SWIM used was stone activated carbon from an online distributor. Also be sure to use a fine filter SWIM noticed the carbon had some dust on it that stained the filter lightly, I would think a cotton ball in a normal funnel would work well but he used a buchner filter with slow/fine paper.