Re: old UV tubes less contrast?

Hi David.

8-10 mins. exposure time looks OK to me. My standard printing time for
"double coated" Vandyke with 8x40W BL tubes (matching electronic
ballasts) @ 1.5" is 8 mins.

The contrast loss that you mention; is it in the form of fogging? (No
clean whites) If so, you may try to mix a fresh batch of sensitizer (if
you're not already using fresh sensitizer).

Also, are you sure that your negatives are contrasty enough? (Have you
printed them before?)

Have you changed (or swithced to a new batch of) paper recently? Paper
change also may cause the contrast difference.

A change in your coating method also can cause a considerable difference
in the results you get (brush -> glass rod for instance or vice
versa)...

The life-span of BL tubes are quite long (around 2000-3000 hours). If
your unit wasn't used in a laboratory environment (but just used
privately), it shouldn't matter whether they're 1 or 5 years old...

Regards,
Loris.
________________________________________

From: david drake (daviddrakephoto@sympatico.ca)
Date: 03/01/06-01:08:24 PM Z

hello

I seem to remember in a past thread that as UV tubes get older they
not only loose speed but also contrast? I'm using a UV printing box
of which I have no idea how old the tubes are. It is also made up of
a motley group of at least three different brands (which is , I
believe, also a no no).
The VDB prints are taking somewhat longer than they should (8-10
minutes @ 3 inches) and, more importantly, the contrast is not quite
what it should be.
I'm debating whether I should buy all new tubes and then I've dealt
with at least that variable as it relates to contrast.

thanks
david

david drake photography
daviddrakephoto@sympatico.ca
Received on Thu Mar 2 03:39:13 2006