Silk Paper On Both Type Rb1

I have what I hope are the 1871 proprietary 1c stamps, that is RB1a and RB1b. Are both the violet and green papers Silk papers please.

Both RB1a and RB1b are silk papers, yes.

Determining whether a first issue proprietary stamp is type a or b can be difficult if you don't have reference copies. The green paper of RB1b (and other "b" types) is a very vivid hue. There is an "intermediate" paper that while it looks "more green than violet" is actually classified as a violet paper, which muddies the water. I'll leave it to others to discuss the technical reasons why that's the case; I'm not an expert on the first issue proprietaries.

If you put the intermediate paper under UV, it shows up as violet. Only the true green paper shows up as green.

I have always had a concern about using UV lights. Is there a specific wavelength used by stampers that is in the safe range, or am I worrying about a non-issue please?

The required wave length depends on what you use it for. Fluorescence, mostly, can be detected with a long-wave lamp. Phosphorescence may react to short-wave, long-wave, or both.

Long-wave lamps should not be of much concern. I would not 'play scanner' with the lamp and hold it at a few centimetres from your eyes and look into it. But with 'normal' use, there is not much of an issue.

Short-wave lamps can damage your eyes. So, do not look into the light. But most short-wave lamps will come with protection so you can direct the light away from your eyes.

What wavelength and how powerful of a UV lamp is needed? I just tried both short and long wave on my Leuchtturm handheld (uses 4 AA batteries) and even in the dark and with fresh batteries it didn't reveal meaningful differences across 1st issue RBs.

I don't actually know the specifics of the lamp at the PF, which is the one I have used to tell the RB papers apart. The wavelength is the opposite of the one needed for seeing modern tagging.