Abstract: Empirical studies have shown that over 30% of electrical machine failures result from insulation failure. The temperature-rise, which electrical machines may safely withstand is determined by the limiting temperature of the insulating material used in them. This study presents, the experimental results of a research to qualify some paper insulating materials thermally by determining their insulation class. Ten sample varieties of Nigerian paper products were experimented with to determine their insulation classification. The samples were cut into definite dimensions and weighed. Each paper product was made into two samples, one sample was left in its ordinary state while, the other sample was impregnated with insulating varnish. Both samples were subjected to a heat run in a sealed industrial oven, while, measuring the insulation resistance of the given sample at regular temperature intervals, until the sample burns out. The measured values of weight, insulation resistance and temperature are shown in tables. Curves were plotted to show the variation of insulation resistance with temperature. From the experiments, seven of the paper products require impregnation to be suitable for class Y insulation, whose maximum permissible temperature is 90°C. The other three paper products are unsuitable for class Y insulation even when impregnated.