Improvements relating to methods of casting solventless synthetic resins

An electrical component such as a transformer is encapsulated by placing it in a moulding vessel which is located in a chamber connected to a vacuum pump, a supply of toluene and a supply of uncured solventless synthetic resin. The chamber is evacuated and the transformer heated to remove moisture &c. The vacuum pump is then disconnected and a small amount of toluene admitted to the chamber which is immediately filled with toluene vapour owing to the low pressure therein. After the vapour has permeated the transformer, the chamber is again evacuated and the moulding vessel is filled with resin. The pressure in the chamber is then raised and the resin cured. As the pressure is raised toluene vapour in any cavities in the resin condenses and mixes with uncured resin which sets as the resin is cured. The chamber may be evacuated and filled with toluene vapour several times and the moulding vessel may form a permanent casing for the transformer.