Question on Plate Printing

We are having an overseas company make a print on porcelain plates. As I understand, they use a halftone screen printing technique for this, similar to CMYK book printing. Although I don’t know much about plate printing and what type of printing it is, I can see some moiré problems on the print. It wasn’t there on the original artwork nor on the digital image. Upon closer look, it seems like they are using the same screen angle on at least two colors, for example Magenta and Cyan. Their halftone dots have a strange squarish shape with а dot in the center.

Moire example here https://flic.kr/p/2pb9JYn
Original artwork detail https://flic.kr/p/2pbbutE
Magenta angle here https://flic.kr/p/2pbbdzK
Cyan angle here https://flic.kr/p/2pbbzBF
Rosetta pattern https://flic.kr/p/2pbbdzp

So I am wondering if there are people who could give some advice on this as I am not in direct communication with the plate making company. They are overseas company and we don’t speak the same language.
1) I’m confused if the same principle of screen angles applies on this since it uses halftone dots. The company supposedly has been in business for many years successfully. So it is hard to believe that they are making mistakes on screen angles.
2) Reportedly they said that we also have the option to use stochastic printing on this project but said it was more expensive. Is a stochastic screen more expensive than a traditional AM screen? Also which of these two methods would be more suitable on plate printing?

 

Hi sir
Moiré patterns can indeed result from incorrect screen angles, and it's unusual to use the same angle for two colors. The strange squarish shape you describe might be a result of a misalignment or a different halftone method.Confirming the screen angles and discussing your concerns with the company could help address the issue.Stochastic printing is generally considered more expensive due to its finer detail, but it can minimize moiré patterns. Its suitability depends on the specific requirements of your project. Discussing cost and output quality with the company might help you make an informed decision.Consider seeking guidance from a local print expert or consultant who can bridge the communication gap and provide insights into the best approach for your porcelain plate printing.

 

This is wise Advice from Adil hope you're project is a success

 

Thanks Adil,
I agree. The first rule of thumb in haltone printing is probably screen angles. But they did use the same angle for Cyan and Magenta. I mentioned this to the artist who is in direct contact with the printing company. The artist went abroad to make the second test print of the plate. Hopefully they are discussing this issue and making better decisions to solve the problem. I am the designer of the project. Unfotunately I am not able to go to the plate making company or find a local print expert who can help. But thanks again for your confirmation and support.

 

Can you post actual photos instead of links to a third party website? It’s quite easy and the results would be preferable to the links to photos you’ve already posted.

In offset printing AM and FM screening costs the exact same in the production process and I’ve never heard of charging more for FM (stochastic).

The type of printing you’re talking about is obviously not offset printing and I don’t know if plate printing utilizes the standard 4-color process printing method, and/or if the inks used are opaque or transparent.

 

Alibryan,
Good suggestion. I will try to post the photos here. I also thought that AM and FM screens should not differ in price. Since the only difference is placements of the dots and it doesn't cost extra electricity or anything. Seems like the company is not very honest about the price.
I would consider it offset printing because it uses the same method as described in Wikipedia > > >"Offset printing is a common printing technique in which the inked image is transferred (or "offset") from a plate to a rubber blanket and then to the printing surface." >>> They are transfering the image to a rubber stamp (obviously the shape is different than the roller type blanket) as dot patterns and pressing on the plate.
I don't know what kind of ink is used. The ink seems to be more transparent than the book printing inks. But the base colors are CMYK, and they add a few more spot colors on certain areas with higher saturation.

 

Press Thumbnails to view in larger size.
Original artwork detail
Moire pattern example
Cyan channel Screen angle
Magenta channel Screen angle
Rosetta pattern

 

Hi ,
I am not the Printing Technologist, But according to my Experience in Offset Industry, your Printing Quality Issue is DPI/LPI on PS Plates.

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