Originally, I thought of this as a reply to @Colin_Adams but I changed my mind: the information could hopefully be of use to more people.
See http://polymerphotogravure.com/tutorial/image-exposure-calibration.html. That site offers a 51 step test file for you to download and use whenever you want to print on a new kind of paper (or using a new printer or a new kind of ink).
Even if they talk about PS, you can perform the same wizardry using The Gimp.
Hello Claes, one of the first lines reads:
“This approach is a simplified but effective way to create a positive for polymer photogravure.”
Don’t know what that is/why I should use that.
Morning, Paul!
Que? A polymer photogravure is nothing but another way for you, The Artist, to express yourself!
I have to admit that the only reason for my including that link was that it contained the important 51-step-test file that you need to find the limits of your printer/paper/ink.
Here is a better explanation: Cookbook - Setting Black and White Points for Printing
Why would you do this instead of making a proper ICC profile with black point compensation?
Morning, @Morgan_Hardwood!
Ah, just because that simple (and quick) method produced better end results than my making a proper ICC profile.
(Hm, logically, this must mean that I did not manage to make a proper ICC profile 
)
Sigh.
Color management… Sometimes it is impossible to find the correct type of toad which the ICC witch’s brew calls for…