i,m a builder so i use clear glazing silicone it does nt have acid .i found this method one day in shed when i was looking for some to get the black engine high heat silicone offmy hands after using it to seal around exhaust flange.i grab,d some petrol to wash it off thinking it was like washing off grease but it just smudged it on my hands and i thought hang on petrol doesnt affect silicone so try,d it on tank decals and worked ,just get a tube in a gun ,but i always punch holes about 2-3mm in decals to let breath and smear silicone very thin and even .then gently with wet rag or turps wipe out excess till sitting flat .it works great and they dont come off.