A strange dot shape?Who knows?

[Bloodsaler]

I got a magazine from German maybe anywhere else. I only know English and Chinese.
When i use a magnifier to see the dot shape more clearly,I found a strange thing.The dot shape is different from the traditional dot shape in our contry.The dot shaple of the magaznie is ellipse,thats not strange.But most of the dot have a blank hole in its cnter.So I confussed.I never work with this kind of dot shape,we usually use is FM or AM.the dot shape of AM is Euclid.
So i photoed this dot,and upload it in this forum.Can any body tell me what kind of this strange dot is?If anyone can send some information about this dot ?
Thanks

 

[color_matters]

hmmmm... that is weird, I've heard of concentric dots but those dots are cenrtainly weird you can find more info on concentric dots at this link

Signature Offset :: High Definition Printing

 

[VladCanada]

A magazine was printed with flexo plates... probably.

 

[Bloodsaler]

I`ve asked somebody do gravure.He judged this produciotn is print with gravure.But does it usual to use light coated paper printing with gravure?esp a magazine~

 

[gordo]

A magazine was printed with flexo plates... probably.

I think that you are correct - flexo. The screen is not gravure and it is not concentric screening.

best, gordon p

 

[Deleted member 16349]

I think that you are correct - flexo. The screen is not gravure and it is not concentric screening.

best, gordon p

It does not look like flexo to me. If it is flexo, the pressure is extremely light. Normally one would see a light line near the edge of a flexo dot where the edge of the dot on the flexo plate contacts the paper. Just outside that light circular line is a ring of heavy ink, which is from the ink extruded out from under the dot. I don't see this in these photos.

I suspect that it is gravure. The printed dot shape is not always related to the shape of the gravure cell. I have seen in a technical paper somewhere a picture of printed gravure dots where the ink has come out of the cell before the impression. It might be related to some problem with the doctor blade that wipes the ink off the surface of the gravure cylinder. The result is strangely shaped printed dots.

Maybe there is too much static charge assist applied, which helps transfer ink from the cell to the paper.

Anyhow, my guess is that it is gravure. Look at other areas of the print besides dots. Look at fine lines. Gravure does not print fine lines with nice straight edges. They are ragged due to the use of cells.

 

[gordo]

You're right Erik. My bad. I just had a look at an old National Geographic and it has the same holy dots. So it's gravure for sure.

gordon p

 

[Deleted member 16349]

You're right Erik. My bad. I just had a look at an old National Geographic and it has the same holy dots. So it's gravure for sure.

gordon p

I was pretty sure that I had seen it before. I then realized that I sat in on the presentation of that paper at TAGA in 1997. I looked for it in the 1997 proceedings and found it. The pictures of the dots were very similar.

The reason it stuck in my mind was because it told me that gravure is not so good at reproducing details such as dots and lines. That is why I think offset has much more potential in regular printing and also in the printing of electrical circuits.

The 1997 TAGA paper title.

Impact of Ink/Paper Interactions on Printability of Aqueous Publication Gravure Inks Part IV. - Ink Transfer and Spreading on Paper.

Abstract link. Search TAGA Abstracts | Printing Industries of America - Printing.org

Go to Advanced Search
Document ID 970829

 

[ljgoldberg]

The red flag should have gone up immediately when the 60 degree engraving angle becomes evident. That's very typically NOT offset or flexo.

Regards,

Larry Goldberg
Beta Industries

You're right Erik. My bad. I just had a look at an old National Geographic and it has the same holy dots. So it's gravure for sure.

gordon p

 

[has-been]

I got a magazine from German maybe anywhere else. I only know English and Chinese.
When i use a magnifier to see the dot shape more clearly,I found a strange thing.The dot shape is different from the traditional dot shape in our contry.The dot shaple of the magaznie is ellipse,thats not strange.But most of the dot have a blank hole in its cnter.So I confussed.I never work with this kind of dot shape,we usually use is FM or AM.the dot shape of AM is Euclid.
So i photoed this dot,and upload it in this forum.Can any body tell me what kind of this strange dot is?If anyone can send some information about this dot ?
Thanks

Bloodsaler:

My first impression is that the dots are snowflaking and, if so, the printing unit is underpacked by approx. one thou. If I am correct you would probably see a different dot shape as the pressman has to carry a heavier ink film to make up the difference.

Regards:
Has-been

 

[Liz Scherer]

This is most definitely gravure.

In publication gravure printing, presses are equipped with electrostatic assist, which utilizes electrostatic force to pull the ink up out of the cell and onto the paper. The inks are very low in viscosity. Surface tension will cause a meniscus to form in the ink in the cell. In cells of lower volume (lighter tones), the ESA seems to accentuate the meniscus, pulling the ink up still more at the edges, so what prints is that characteristic doughnut shape. Centrifugal force of the turning cylinder also affects the shape of the printed dots.

So the gravure process printing does not result in a moire' pattern, each color is engraved at a different angle, hence the difference between the cells of similar size but from different colors.

 

[Liz Scherer]

And in answer to your question about gravure and magazines, yes, that is very common, especially in Germany.