In most cases, the correct way to differentiate would be to talk about pure metal foil vs. metalized foil for the conductive element. Meaning if the cap is made with a pure metal foil, such as copper or uses a metalized foil where a very thin layer of metal is damped upon a foil, which could be polypropylene, paper or otherwise.
And to talk about paper dielectricum vs. plastic dielectricum. Which as explained by Tempo is the insulating layer.
Then to say if a cap is wet or dry. A wet cap could be a paper in oil, a dry cap a normal metalized polypropylene.
And in the case of a wet cap to say if the impregnation happens under vacuum, or is simply "poured" into the cap.
This is of course very rough, an infinite numbers of papers could be written on the subject... :)
And to talk about paper dielectricum vs. plastic dielectricum. Which as explained by Tempo is the insulating layer.
Then to say if a cap is wet or dry. A wet cap could be a paper in oil, a dry cap a normal metalized polypropylene.
And in the case of a wet cap to say if the impregnation happens under vacuum, or is simply "poured" into the cap.
This is of course very rough, an infinite numbers of papers could be written on the subject... :)