NuArc 26-1KS problem (Slow printing times)

[Loris Medici]

Hi all,

I purchased a brand new NuArc 26-1KS plate burner a couple of months ago, for the purpose printing with UV sensitive alternative processes.

I've just had time to use/test it and I think there's something seriously wrong with the device; I currently struggle with pop palladium (Li2PdCl4 + AFO or Na2PdCl4 + AFO, noble metal solutions' concentration 0.52M, AFO concentration 1.05M), and the exposure times are incredibly long.

I was using a bank of UVBL tubes before (Philips 40W, /05 series - not manufactured anymore, replaced with /10 series recently), and my standard exposure time (with a 31-step tablet) was 6:30, giving me 28 distinct steps including dmax and paper white.

With the NuArc, I print for 900 units (17:15), and the step tablet test says I still have to give 1 stop more exposure for being able to get 28 distinct steps, and more importantly I'm currently getting a pretty anemic result with low dmax. Awful. Something's wrong, WRONG!

What is your usual pt/pd (or any other print out iron process) printing time (not units, time!) with this unit? (Or, similar units?)

What could cause the problem? I'm suspecting the bulb (NP-80) but it's a brand new unit and I just don't get how could a brand new bulb work that much slow? (The visible light illumination is pretty strong BTW.)

TIA,
Loris.

 

[clay]

The NuArc units themselves are arbitrary, and can be adjusted by popping the top off the unit and turning the little plastic disk that covers the photosensor one way or the other to adjust the amount of light hitting it. But those times do sound long. When I had the 26-1K ( I have an Amergraph unit now ), my printing times for DOP pt-pd were about 300 units (again, arbitrary, depending on how the photosensor is adjusted) but were in the 5 minute range. Think that it is possible the unit is not getting enough power? What about the cover glass on the vacuum frame? Is it the original glass? I have heard of people replacing the glass and putting UV screening plate glass in its place and having exposure issues. Not much help, but that is all I can think of.

 

[Nicholas Lindan]

The sensor is normally set so that with a new bulb 1 unit = 1 second. If your machine hasn't been reset then your bulb output is a bit low as 900 units should take 15 minutes rather than 17 (however +/- 20% is within the setting tolerance of the sensor). This alone does not account for the discrepancy you are seeing.

Old bulbs are the #1 cause for long printing times. The bulb should be clear or with a light milky haze. If it is very milky, darkened or has a bulge then it is time for a new bulb.

To see if the frame glass is the problem, coat a small scrap of paper and lay it on top of the glass and expose it. If it turns black in a much shorter time then the glass should be replaced. The frame will most likely just have plain float glass, this isn't a problem in graphic arts applications.

Another problem may be your line voltage. If you have a volt meter then check the voltage when the unit is running. Some machines have adjustable taps on the transformer to accommodate low line voltage.

 

[sanking]

Also get a SPD of the bulb in your NuArc to make sure that it puts out radiation in the range where platinum/palladium is sensitive. NuArc made bulbs for diffferent types of printing and you may have one that is not effective for platinum printing because of the range in nanometers of the radiation. A SPD chart will show in what nanometer range the bulb is putting out radiation.

Sandy King

 

[Loris Medici]

Clay, I run the unit in a dedicated line and dedicated power regulator. Input is perfect; 220V 50Hz - this is a special unit manufactured regarding our electricity standard in Turkey. Thanks for quoting your experience, it seems that I need more than 1800 units with my plateburner. (Process: Ziaytype.)

Nicholas, 1 unit = 1.15 second with my unit/bulb. The unit is brand new (imported from the States, directly from the manufacturer) and the bulb is crystal clear (the wires also are clear - not looking old). No extra bulge (other than the original suction bulge) in the envelope. I'll test the glass as you say. BTW, the glass is the original glass which came with the unit.

Sandy I replied to that elsewhere but will repeat here for others. See the SPD here.

Thanks all,
Loris.

 

[Don12x20]

Loris
You didn't mention the negatives.
By any chance are you using a pyrocat developer?
(more later if this is the case. Bulb spectra may be significantly different)
Don

 

[Loris Medici]

Don, I think I mentioned I was testing with a 31-step tablet. Thanks anyway...

 

[Loris Medici]

I'm an idiot...

Dear all,

I'm an idiot; it wasn't my NuArc 26-1KS. I just found out that I was
trying to print on non-acidified Fabriano Artistico, hence the anemic
bad results and long printing times!!!

The problem is that I wasn't doing iron printing for a long time and
forgot that I had trimmed Artistico sheets and - due lack of storage
space - put them into an empty COT320 box! Therefore I confused
trimmed Artistico stock with COT320. I only noticed this only after
opening a new COT320 box.

Adage: Never put something different - than the original stuff - in a
container, and if you do so mark the container in a big / bold /
colored / eye-catching manner!

Thanks all for the suggestions. I have been an idiot really... (Blushing)

Regards,
Loris.

P.S. First test with good paper indicates that I'll get <=10 minutes
exposures; 6:30 or 8:10 or 10:20 - depending on your Dmax evaluation.
(You know, it's a little bit complicated with print out processes;
often, you won't have two merging steps in the step tablet test.) I
think I'm going to standardize on 8:10, which is ~ 420 units according
to my light integrator... (It will give me 29 / 30 steps incl. pure
white and black.)

 

[MVNelson]

I'm glad you figured out the problem. My first thought was that something happened with your process rather than the equipment. I had a similar experience early on when my first exposure times were 150 units (2.5 mins) and suddenly went to > 6 mins before I realized I had pulled the wrong paper off the self. My unit has 1000w , 3000w and 6000w settings so short times possible.

 

[Jim Noel]

The sensor is normally set so that with a new bulb 1 unit = 1 second. If your machine hasn't been reset then your bulb output is a bit low as 900 units should take 15 minutes rather than 17 (however +/- 20% is within the setting tolerance of the sensor). This alone does not account for the discrepancy you are seeing.

I have seen the reference to one unit = one second in other posts. Is this one unit, or one tenth unit whichis about the speed of mine.
ShouldI speed it up by adjusting the integrator?

Jim

 

[Loris Medici]

It's exactly one unit. The manufacturer's original calibration could off by +/- 10% - probably because of slight variations in the placement and swing angle of the eye...