Thread: GTOZ Alcolor dampening probelm

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thanks for all the info!
I'm just not ready to give up on Alcolor.
I tried to work with de-integrated water-ink units(that is, with the Z roller disconected) and needed less water to work... but...

Now i find impossible to find water-ink balance. I get to a point (#3 in potentiometer) where there is too much water(you can see it in the solids) and with the drop of only two 10th(that would be 2.8 in potentiometer) i start to get scumming in the plate. I'm not new to offset printing. Not even new to heidelberg printing. just new to alcolor printing and, by experience, i can tell this behavior can't be normal for a "built with precision, known for reliability" heidelberg press.

I'm willing to try and diagnose this problem by some experienced operator and/or demostrator over internet video(Skype) if someone feels that's possible and quote a fee for it.


Thanks again to all

hi,
better to check the roller surface properly, or change the roller and try. can u give me some more clear ideas about the problem

Maybe you have set the metering roller too hard on the water pan roller. Z-roller, is that the indermidate roller you are talking about?

I've tried metering roller at diferent pressures(from 1/4 turn to 1 1/4 turn) with same results. the intermediate roller is the one that can either connect or disconnect water and inking units by means of yellow ink roller.

Ombre, my question is : by Z-roller, do you mean indermediate roller? Make sure , that your alcohol doser is workink. Get a manual alcohol meter ang make sure that your alcohol percentage is 8-10%. What plate are you running? If you run plates like eg. Presstek you need a lot predampening at every startup, otherwise you get scumming. Try another additive. I prefer Prisco type 3551 plus2 at 7%. If you haven 't set the dampening rollers correctly, dont bother. But I believe that this is the first thing that you did.

By Z roller i mean the roller that touches the water form and can conect also with yellow inking form roller(i guess "intermediate" is the name for that roller, but not sure... would that be the intermediate roller?)

I'm rigth now at 9% according to our 1/2 year old Royse hidrometer.(i have to add like 11 real percent of alcohol to get that reading) The plate are fine, we run them on our other (non alcolor)presses. My problem is that i can not lower water enough on the plate in order to achieve balance(and a decent print)

Example: Since the beginning of the run i get a very shinny plate and, as i start to lower water amount, a very rare effect takes place: The layer of water on the plate starts to breake at one or several spots on the plate(it looks very much like the red sea breaking in the"THE TEN COMMANDMENTS" movie) and start scumming there while the rest of the plate remains with excess of water. I looks almost impossible to have scummnig in one inch of the plate and scumming in the very next, but that's exactly what is happening.

The setting of rollers looks fine:
water form to water distibutor(matte): 5 mm
intermediate roller to water form: 2-3 mm
Metering to water form: 5 mm
Water form to plate: 3mm

Thanks for the 1000th time
Moe

ΗΑΗΑΗΑΗΑ The ten commandments...Thanks my man!!

ok.. now..I didnt ask you if your plates are fine . I asked which plate do you use. I have seen a presstek plate running on a GTO 46 with Fleech dampening rollers with tab water and nothing else, but on alcolor you need predampening, like 15 cycles and 10% IPA and 8% additive (prisco that is)for the exact same plate. Your problem seems to be lack of additive. Get a handheld alcometer, the one that looks like a testtube, and get your chemicals right. I nad this problem twice, Once was lack of additive, and the other was lack of alcohol. When its lack of additive , the ph value isn' t wright, (get ph measure strips from your supplier, they are very cheap) and you also see small water lines on your metering roller


and, YES, that is the indermediate roller.

You're right about plates... I don't know the brand but i know they are filmed in a Bassys print UV setter, Violet plates. They might be agfa, but not sure.

One thing i do know is that they are very friendly as regards of water reception. I mean that you don need that much of pre-dampening in order to start clean from the beginning, and if it gets dirty, it cleans very fast during run. We also run with Xante polyplates and that's a diferent story. They do need predampening.

I see those water lines in the metering roller and see the exact same lines in the plates.

I'm in the process of getting a handheld PH, conductivity tester, but not yet here. I'll get also a alcometer.

If i go with more water additive... How much more should i use? Right now i use 5 oz (or 145 ml)

Thanks

P.D. I want to say that the above movie is one of the best i've ever seen!

I missed to reply, sorry.I dont know oz I use metrical system. I dont know how big your circulator is , so 145 ml doesnt tell me anything. You need a ph value of 5 to 5,5 max. GET the little measuring strip indicators, that tell you the ph value.