Aluminum is the most commonly used material for filters. It has good mechanical properties and provides a wide bandpass while also excluding visible light. Its bandpass characteristics are often modified by the addition of carbon or titanium.
Tin and Indium are used to provide bandpasses at the longer wavelengths. However, tin and indium have relatively short shelf lives, and require proper storage.
Boron and Carbon are used to provide a bandpass in the shorter wavelengths, but they do not provide much visible light rejection.
Polyimide has an EUV bandpass similar to carbon but offers greater mechanical strength. It is used for very large filters and those used to support pressure differentials.
Although most metal foils are free of any pinholes, some submicron foils may develop microscopic “windows” which appear to be pinholes when strongly backlit. These “virtual holes” are relatively transparent low-grade oxide, whose transmission is principally in the red. They tend to occur at only a few discrete points in the foil. If your research requires it, Luxel can “plug” these pinholes when necessary.