Ink Coming through

Hi there,

I’m not sure what I’m doing wrong but the Ink is showing through the back-side of the paper even with a 300gsm cotton paper. What Am I doing wrong?

Vanessa
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Is the tympan dirty, or are you flipping pieces to print on the back side? The latter can cause the ink to offset onto the tympan, and then onto additional pieces.

What kind of ink are you using?

Vroooom has some good points. Here are some more: Is the image on the back the same as the front, you might be placing the printed sheet with wet ink on top of the other sheet before the ink has dried.
Heavy ink coverage needs to have the sheets placed in a drying rack, or one a table so that the sheet can dry.

If it just marks on the back of the sheet it could be a dirty tympan packing as Vrooooom stated.

Assuming you’re using a windmill, are you throwing the impression lever too soon? You’d accidentally print on the tympan, then offset on each sheet if you don’t stop and clean it off.

Hi guys,

I’m using a rubber based ink.

I think Jonsel is right because the whole image on the plate has printed on the tympan.
The guy that was helping me with training said I have to apply the lever pressure on simultaneously when the paper is getting lifted. Is this correct?

When is the right time you apply impression lever?
I’m using a Windmill.

Vanessa
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Vanessa,

I’m learning my Windmill now as well, and I’ve made the same mistake. I try to do it simultaneously and end up throwing it on too quickly. If I recall correctly, you want to wait until the grippers have the paper, then throw the lever. That way, the worst thing that happens is you have a missed or light impression.

Re: Starting a Windmill.

Pull open feeder valve (non-feeding) start press in motion. When ready (presuming feeder is properly set up), close valve with sucker bar coming down on stock. Pull impression on AFTER stock has started rising by sucker bar but BEFORE sheet has been released to gripper (unless running to guides, in which case it won’t matter). Or, if worried about register, run three sheets (for position) ignoring the 1st sheet printed.

Running multiple sheets is also a good way to see what your actual color will be, as it will start out much darker, from all the ink piled on the form from idling the press (no matter how careful you are to throw the impression rollers off the ink drum).