security inks

[kbarz]

having problem with coin reactive in.. after about 6000 sheets the back row of the plate goes blind, makes no difference if it is 6,9,12,16 up on sheet, the back row goes blind .. we are not baking or plates in an oven,( will this help)... normal blankets,0.78 bottcher, ro water with bottcher sub and acid.. any advice would be welcomed... kbarz

 

[Cornishpastythighs]

Unbaked Plates should last a lot longer than 6000 impressions so baking is not the answer.
Has the image actually worn off of the plate?
What kind of ink coverage are you running, probably very little if its security ink.
Are the press operators running minimum ink/water?
Check your plate/blanket squeeze and you should be printing with around .005" Thou or the metric equivalent. Of course you should check the other usual suspects like your ink form roller settings and durometers and that your blankets are nice and tight.
Have you tried the ink in another unit to see if you get the same result? Do you have any issues printing regular ink in the print unit you are running coin reactive ink.
Here is a troubleshooting guide for you that lists both plate blinding and image wear.
Just some suggestions for you.
http://www.monochrom.gr/UserFiles/SFTSG.pdf

 

[kbarz]

if printing 4 up on gripper edge then moving to the tail end the last 4 images from the 12 up form, the plate is visually weaker than the others. This was on man Roland 300 coin on first station, but this also happens on 40 inch 700 Roland,, trying to print with .004 total plate and blanket. .002 +.002..blankets good rollers good enough to print any thing else in shop. in deep shit client rejected 9,000,000 cartons... fellow pressmen it is very hard to print invisible ink,turst me...tks kbarz

 

[Cornishpastythighs]

We run these coin reactive inks a lot and do not see the issues you are experiencing. On very low coverage image areas we have to keep our dampening to the very bare minimum, it seems even more important with this 'invisible' ink. If this issue is happening on both of your presses I guess we can rule out mechanical issues. Is this the first time you have run this type of ink, if not has anything changed since you ran this ink before? different FS,different ink supplier?
Here's some more info on Plate Blinding.

Problemart or all of image on plate does not take ink.

Plate Blinding - Chemical
Plate Blinding - Chemical
Cause:

Fountain solution too acidic
Excessive gum in fountain solution
Plate cleaners and/or scratch removers have dried on plate image
Fountain system contaminated by detergent
Excessive fountain solution in ink
Improperly developed plates; gum adheres to image area


Solution:

Adjust fountain solution to proper pH/conductivity (pH 4.0-4.5)
Re-etch plates and rub up image areas with press ink; replace fountain solution with tap water; if image returns, replace tap water with fountain solution containing less gum
Rinse plate well after cleaning
Thoroughly rinse all washed parts before re-installing in press
Reduce dampener setting to minimum level; consult ink manufacturer Wash plate thoroughly; remake if necessary

 

[kbarz]

tried to talk my boss into going back to the basics in offset printing ,,, but nooooooooooooo... we ran with no problems until we were forced by headquarters to use some off the wall plate.. we were using Fuji withy no problems.. we went trough all that you suggest , but plate manufacture wants us to buy an oven to bake them in.. and only the tail end of the image is going blind. was not looking for another reason to drink but found one ... tks fellow lithographer ,, I will let you know on the next press run how she runs and what we do to help this... kbarz

 

[kbarz]

as stated before,, would let fellow printers updated on coin reactive ink problem.. we shook the tree so to speak, now we are going to have full blown test done on press.. ink company blames ,water mix ,,water mix people blame ink,, both wonder if its the blankets...very tangent,,,, but behind closed doors they blame operator.. results of testing to come soon...kbarz