You want a ceramic-based glue (eg: active ingredient is sodium silicate - aka rope glass) rather than silicone.
Ceramic based sealants will transfer heat, whereas silicone ones usually will not.
If the resistor is too small for the hole in the J-head block, I tack the end of a strip of aluminium foil to the body of the resistor with ceramic based glue, then wrap it around the body of the resistor to fill up as much of the remaining space as possible. I then trip off any excess foil, so the fit is snug. The alu foil will conduct heat a lot better than silicone (or even the ceramic-based glue), so use the alu foil to fill up as much space as possible.
Some options for such glue:
1. Makergear ceramic adhesive (ships from the US tho).
2. Fireup Pyrogrip - Sodium Silicate based. I'm in Victoria (Aus) and bought a small 200g bottle for ~$10-12. Supposedly rated to 1200 Deg C.
If you're searching for someone/something local, look for Sodium Silicate, high temps 800+ Deg C (we don't rely on the temp, but it means the components are suitable for the job). Most of this stuff is used for fire prevention work (eg: securing fibreglass rope seals on fire heater doors, etc) so places that specialise in that sort of stuff are a good place to start.
Note: Some sodium silicate products are slightly conductive, so protect the leads of the resistor from contact with the glue. Ideally, you don't want the glue on the ends of the resistor at all - you want a tiny amount on the device to hold it in place and that's it.
Ceramic based sealants will transfer heat, whereas silicone ones usually will not.
If the resistor is too small for the hole in the J-head block, I tack the end of a strip of aluminium foil to the body of the resistor with ceramic based glue, then wrap it around the body of the resistor to fill up as much of the remaining space as possible. I then trip off any excess foil, so the fit is snug. The alu foil will conduct heat a lot better than silicone (or even the ceramic-based glue), so use the alu foil to fill up as much space as possible.
Some options for such glue:
1. Makergear ceramic adhesive (ships from the US tho).
2. Fireup Pyrogrip - Sodium Silicate based. I'm in Victoria (Aus) and bought a small 200g bottle for ~$10-12. Supposedly rated to 1200 Deg C.
If you're searching for someone/something local, look for Sodium Silicate, high temps 800+ Deg C (we don't rely on the temp, but it means the components are suitable for the job). Most of this stuff is used for fire prevention work (eg: securing fibreglass rope seals on fire heater doors, etc) so places that specialise in that sort of stuff are a good place to start.
Note: Some sodium silicate products are slightly conductive, so protect the leads of the resistor from contact with the glue. Ideally, you don't want the glue on the ends of the resistor at all - you want a tiny amount on the device to hold it in place and that's it.