What's this under Sealant?

[matt_matt]

Currently removing old sealant around bathroom window frame and notice that in some places there is a gap between window and tiles, the gap is no bigger than 5mm width but tool does go down quite a bit but it's been filled in with something similar to sealant, is it just more sealant? it may well be but it's a different colour to the stuff that was on top. I've left some sealant on to show difference but its pretty much the same texture. Is it best practice to remove all of this? I know I'm supposed to remove all of the old sealant to make sure the new sticks fine, will the new sealant adhere to this or shall i remove it all and fill the gaps in again with the new sealant or some other stuff? Cheers

 

[CBW]

Silicone sealant or mastic sealant.

 

[matt_matt]

Silicone sealant or mastic sealant.

Will new sealant stick to this or is it best to try and get rid of as much of this as i can? It does fill in the gap between tiles and window so i'm guessing i'd have to get something to fill in the gaps again if i did take it out

 

[CBW]

Yes should go over it, be mindful of any parts of mould present, as you’d be trapping the mould