Exposing Carbon Mask for width and than depth for Gravure Cylinder Cell

[Mustafa Umut Sarac]

Tiefdruck , Tiffdruck, Rotogravure is a printing press technology which uses half toning as a continious tone generation. But additionally
this system uses depth information for each gravure cell. You can create a %95 black dot width with screening at half toning but depth information changes how much ink does this dot width receive.

I read before laser, mechanical, electric inventions , these cells were created on copper cylinders with carbon tissue mask exposed with film and than etched with acid.

I read that the process was to expose carbon tissue for width information - I think with the help of screen - and than second expose with another continious film for depth information.

Why two exposes ? Why single expose does not give cell depth information also ?

edit: I think this is for special treatment and could be used by better control for many processes if you can plan.

Thank you,

Mustafa Umut Sarac
Istanbul

 

[artonpaper]

I would think cell depth would be a function of the etching process as opposed to exposure. In copperplate photogravure, the plate is etched in as many as ten different strength etching baths that start with stronger dilutions to etch deep into the shadows and end with weaker solution to get lightly etched highlight detail.If what you say is accurate then obviously there is something peculiar to rotogravure.

 

[Mustafa Umut Sarac]

Artonpaper;

Do copperplate photogravure use an different thickness and hardness mask to be used as a function of etcher acid solution ?
I read above at Linotype Hell where they were talking about even an older 11 step process which takes 4 shifts for 4 color gravure preparement. May be you are talking about older process covered at their article.

Umut