Gutta-percha sheets are also used and answer well.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler
5. Gutta-percha bougie, for dilating the opening of the teat.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler
No dry insulation of the nature of indiarubber or Gutta-percha will withstand the high pressures that are brought to bear upon the circuits of an oscillation transformer.
"Hertzian Wave Wireless Telegraphy"
John Ambrose Fleming