Re: Cyano as the first layer for color gum prints? BL or BLB bulbs...

On Mon, 19 Sep 2005, ryberg wrote:

> Carmen,
> Both BL and BLB tubes are essentially the same except the BLB tubes
> have a blue coating which cuts out almost all of the visable light. There
> are two reasons for this. The main one seems to be so the light is not seen
> but the effects of it are in stage productions and partys. Paints which
> react to UV glow brightly but everything else is in near darkness--quite an
> effect. The other reason is that the filter is thought to filter out much
> of the damaging effects of the UV on eysight--I doubt this to be true, but
> have read it in several places.
> Charles

Thank you, Charles -- at last, fact not opinion. I'd add just one point...
dichromate is ALSO sensitive to wave lengths within the visible spectrum,
that is, wave lengths that are cut out by the coating on the glass to make
special spooky effects in night clubs. Which is why the plain BL bulbs
that do emit some visible light are indeed faster -- as my side by side
tests (testing with borrowed BLBs) showed consistently.

I realize that some folks claim there's no difference -- possibly with
some emulsion/paper/bulb combo I haven't tried, but not IME.

If it matters -- which I doubt it does since the difference was (as i
recall) never more than 1/3. However, I don't recall the rating on the
blue light, it's possible that is MORE damaging to the eyes, since the
lower you go the more harmful, n'est-ce pas? And with the lower visible
light you might be off guard.

Which is to say, keep your eyes out of ALL of it, including incandescent.

(Is that more than one fact?)

Judy
Received on Mon Sep 19 22:21:26 2005