Vary nice generic and generalized information.

If you need or want information on the exact nature of any Wratten filter, then consult the Wratten section of the Handbook of Physics and Chemistry. There you will find any and all details of stability, life and spectral range (including lab made filters, these are the non-gelatin materials, made with liquid and glass containers,) such as polarizers and neutral density, called atuators*.

To bring a fine point to it, the only designated 'blank' filter is the basic gelatine filter marked as the 01 Wratten that is just the gel base itself and there is a density, spectral values and optical displacements and stability/life of the unit. That is technical support that is of value, the rest is just hear say.

*The atuators are designed to pass almost all visible light and will stop 'equally' the specific volume of visible light. This is why a polarizer or ND will remove the visible spectrum but will pass much of the IR, so with a digital camera set up for IR work can still be used to 'mix' visible and IR areas for creative control in general photographic work.

The old IR film that is still made, falls into this category. Without ND or a polarizer, the IR is too low in sensitivity, but with ND and polarizers, one can make the film mostly or totally IR responsive. Mixing the two (IR and Visible spectrums delivers powerful visual results to the photographer) creates a powerful tool for IR work that goes beyound the simple range of just IR imaging.