Attention optics/film experts

[Javelin]

A company I'm involved with makes a few renewable energy products. I can't say very much here but I have client question I need to answer by the weekend.

what we have is a parabolic reflector that focuses on a narrow band on a special pipe where we make steam inside. the question is whether the reflector reflects beyond the visible spectrum of light and into near infrared. they require infrared up to 1800nm wave length. So I need to test this. what come to mind is not only can it reflect that wavelength but is it still focused or is it scattered. I don't have any tools like a spectrometer or anything so I intended to use IR sensitive film and make a small emitter and test this in the dark. I hope to see a narrow band of exposed area in the middle of the film. but I don't know how to see that would I need to get the film processed?. I'm pretty sure I can get sheet film from Kodak or Fugi (I built machines for both companies for packaging these film sheets) and i'm not sure if I have to ask for it to be sensitivve for a certain wavelength or not. I already tried my F717 on the reflector and know it is reflecting at least up to 940nm and pinsharp (using nightshot) but I'd like to be able to know for sure for the rest of the range. Any other ideas whould be great too.

[Javelin]

I was hoping just to be able to expose the film

[Javelin]

I think your right. Alao at some point mid IR become heat rather than light. some say between 1400nm and 1mm it's all heat.