Using Nu-Arc 26-1ks
- --- In PPLetterpress@yahoogroups.com, "Elizabeth Gross"
>metal halide machine. Results? Vague timing?
> Has anyone used a Nu-Arc 26-1ks for polymer plates? It is the newer
Liz, I used the Nu-arc 26-1K for years. It is not ideal, but it works.
Exposures are longer than with a bank of UV tubes; as I recall it, for
a solid or reverse I used 125 light units, 250 for a medium image, and
for finely detailed type 400 to as much as 800 light units. That's
something like 40 minutes. And exposure times increase as the lamp
ages. For non-critical images I also made a tube of index stock and
placed it over the glass to concentrate more light--which also
broadened the slope of the beard.
Consider also the glass contact frame--you can't massage out any
air bubbles as you can with a flexible cover sheet. Matte-emulsion
film (or a matte plate like Rigilon HX) will improve drawdown. But
most important is trimming all four edges of the plate so there is no
lip. (The lip forms on the outside of a cut, and interferes with
When the drawdown is complete, and you can see the Newton's rings
between neg and glass, every single speck of dust or hair becomes
visible. Make sure none are in the image area!
--Eric Holub, SF
ps-the unit has a vacuum relief valve. Leave it open until the blanket
is drawn up to the glass, then slowly close the relief valve until you
get full vacuum.