you can get a sealant remover normally messy as it just makes silicone go tacky
best way is stnley knife
new sealant depends on what type of windows they arre example pvc = low modulus silicone
alumiuim = highmodulus silicone i could have them mixed up it says so on the tube
but mastic is best for wood tremco is brilliant but takes ages to dry months sometimes
mark sneyd
June 2009