I have a bay window that had some old crusty sealant filling in the gap between the plastic window panes and the original oak internal window sill. I am not sure what type of sealant it was, but does appear to have been painted over at sometime. It is pretty rock solid so I don't think it's silicone ( unless that's what happens to 50 year old silicone sealant?) if I heat it with a hairdryer it does give just enough for me to remove it bit by bit ( becomes slightly stretchy) . Any ideas what this is ?
I need some advice on what to use to refill this area, the gap is fairly large ( up to 8/10mm at some points along the window ) . It would also needs to be mould resistant and water proof and relatively easy to apply ( plus something that would last as I really don't want to be doing this again for a long time ! ) Any advise or recommendations would be really appreciated.