Interdens is one of the oldest intumescent available in our collection but don’t let that make you think it is not up to the job. This product is a true pedigree in the world of intumescent seals. The key to its success is the little or no pressure created on its expansion, and that is right throughout its production of foam well into a fire test. The resultant char is an excellent insulator for the surrounding timbers and glass edge working to enhance their ability to restrict the passage of hot gasses. Not widely used in today’s competitive market but in our opinion, Interdens offers a highly competent performer for the modern glazing specifier.