Transparency appearing from nowhere...

[Jae32399264rj4s]

I have a client supplied Indd file. It's set up and an entirely CMYK document with no transparencies, overprints or anything else, so in the Indd file itself everything is all fine and dandy, but when I export a PDF one element has a transparency applied.  For whatever reason, a box with only a black fill 0/0/0/100, acquires an overprint setting that shows in the final print pdf. Opened in Ai/Rip software, overprint is switched on, but not in Indd. What could cause this setting to be applied and, is there a solution?

Attached are screen grabs of the affected piece.

[Willi Adelberger]

Pure Black will always overprint per default. Change the value of black from 100% to 99%.

[Jae32399264rj4s]

I had that idea too, and added 1% CMY to the mix and the overprint went away. Which is great and all, but what's the point in default applying overprint in 100K but not 99K? What benefit is there?

[Jae32399264rj4s · Accepted solution]

I did find that un the settings, under appearance of black, Overprint of black swatch at 100% was turned on. Turning it off fixes the problem. Question is, why is it turned on by default?

[Eugene Tyson]

There is the setting for the black to always overprint - which you have found. 

I wouldn't alter client supplied files by altering the colour percentages. 

Glad you found the setting and all is good. 

It's set up and an entirely CMYK document with no transparencies

By @Jae32399264rj4s

InDesign doesn't have a colour mode - it can contain a mixture of colour models, RGB, CMYK, Spot colours etc. 

Transparencies are typically anything with a Blend mode or the Opacity adjusted in the Effects Panel. 

Or other situations with imported images etc. 

If you go to the Pages Panel sub menu you can set up icons to appear beside the pages panel - including a transparency icon that will show if there is transparency on the page/spread

And it's super-annoying for me that InDesign black is overprint and Illustrator is not. 

I switch between both apps all day, and somehow, this inconsistency in the software's behaviour gets me at least once a week. 

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Changing black overprint behaviour in the preferences means it's document-wide, I don't know if it's intentional for you to have smaller black text say for example knockout of elements, which may cause trapping issues. 

If it's just for a particular area then a special swatch of Black 100% would be better than changing the entire document behaviour. 

If you create a new swatch it won't be default overprint - only the InDesign Black Swatch (that you can't delete) is default overprint.

You can read about that here

https://helpx.adobe.com/ie/indesign/using/overprinting.html#:~:text=Knock%20out%20black%20objects%20....