insulating properties of silicone

Oh yes! In my TV servicing days I used to seal the CRT EHT connector with silicon rubber sealant between the cap and connector, especially where the set was installed in a mobile home or house where they used a calor gas type heater. The clear stuff was excellent but I had a load of comebacks from a short period when I used white bathroom type silicon sealant. Black tracking marks right acoss the inside of the cap through the sealant, in one case it was so bad that the arcing had etched the glass around the crt connector! I only ever used the clear stuff after that.

Roy

Right but isn't the bathroom stuff "caulk" and not 100 percent silicone?

Right but isn't the bathroom stuff "caulk" and not 100 percent silicone?

Some is, some isnt. The "texture" seems to vary a lot. Some are like the stuff used for sealing around double glazed window frames i.e. rubbery, others are definitely pasty in texture. The pasty ones are a definite no go electrically. However, the white stuff that I used was the rubbery type. Evidently the white colouring included in it was enough to promote the arcing. I only ever used the clear stuff after that and had no further problems. Having said that, I have seen white stuff used by manufacturers on flyback transformers and EHT rectifier slabs apparently with no problems.

Roy