Quote Originally Posted by Gerald C Koch View Post
There is no difference between 99%, 91% or 70% isopropyl alcohol other than the percentage of alcohol in the mixture. Since 70% is so much cheaper, often on sale, just use a bit more.
My experience is different as I have found there to be some sort of mineral oil in the 70% with coats my negatives, leaving an oily sheen. Perhaps it is just the brand I purchased but for the extra 73 cents between the 70% and the 99%, I would get the better stuff. I actually purchased 4 bottles at Costco for $5.75 which should last 10-15 years. I also use it for cleaning (along with q-tips) as it evaporates almost instantly.