Precision Resistors - General Thread

[sahko123]

Is there any particular reason certain oils are used? Is because of corrosion issues? Or even humidity issues?

[leighcorrigall]

Is there any particular reason certain oils are used? Is because of corrosion issues? Or even humidity issues?

Some oils spoil or are corrosive because of contamination. Other factors are heat transfer and high-resistance insulation.

[bsw_m]

I has measure diameter of glass insulated cast microwire from 100 MegaOhm resistor.
Wire without insulation: 2um 
Wire with glass insulation: 14um
Sorry now I cannot take the microwire photo from my microscope when I don't have the photoattachment for my microscope.

P.S.
I try take photo from eyepiece with phone camera. Quality not good, but..
625x magnification.

[TimFox]

Is there any particular reason certain oils are used? Is because of corrosion issues? Or even humidity issues?

Some oils spoil or are corrosive because of contamination. Other factors are heat transfer and high-resistance insulation.

Before I retired, we used Shell Diala^TM transformer oil for insulating high-voltage supplies.
So far as I could tell, it was basically pure motor oil, with BHT (or similar) added to retard oxidation.
Butylated hydroxytoluene is an anti-oxidant, whose use in food is controversial.
(For high-voltage purposes, it was necessary to pump a vacuum on top of it to remove bubbles.)