New test methods were developed to characterize the high temperature durability of intumescent mats that are used to mount ceramic catalyst supports in stainless steel cans. The key attribute of these tests is the use of an electric resistance heating method to maintain a temperature gradient through the thickness of the mat when a cyclic or constant shear stress is applied to the mat interface. These tests are simple to perform and do not require expensive equipment or highly skilled operators. Using these new test methods, the durability of ceramic preconverters mounted with 4070 gm/m2 intumescent mat was studied. The results of these tests indicate that a preconverter package with 4070 gm/m2 intumescent mat can perform satisfactorily in the close-coupled application where temperatures exceed 900°C.The mat performance can be quantified in terms of applied stress and test temperature by utilizing the experimental methods described in the present study.