Jacques,
You should have no problems whatsoever, with standard plastic developing
tanks. I develop Kodak high Speed Infrared, Konica 750 IR , and Kodak
Ektachrome Colour IR slide film, in standard plastic tanks (Paterson,
and Jessops) and have never had any trouble.
I have checked the opacity of these tanks ( Infrared sensor inside tank,
and a one kilowatt tungsten light source outside tank) No Problem!.
It is essential, however, that you load camera,and tank in ABSOLUTE
darkness especially when using the two Kodak films. If you do have any
doubts about your developing tanks, develop in subdued light
With regard to the light in your darkroom fogging the film even when
switched off, you may consign that to the file labelled nonsense!!
For unless the light source when extinguished remains at a temperature
in the region of 300 - 450 degrees celsius, it is highly unlikely to be
emitting Infrared in the sensitivity range of the films. A standard
darkroom safelight will present no problems when switched off.
Alex.
-- Alex Nanson alec@norlex.demon.co.uk Gloucester. UK