Had the same problem on my SCT. Sap, with pollen all around it. I tried Kodak cleaning fluid and got streaks. Tried 90% isopropyl and got streaks. By then I had gone through half a bag of cotton. Then, I breathed on the streaks and wiped. They disappeared. Don't worry about scratching, I wiped like a Neanderthal after awhile. I was sure I had ruined it, but all is well.