What inkset are you using and on which printer? My apologies if you've already mentioned this, but at a quick glance at your posts in this thread I couldn't see this info.
I use Piezography inks in an R1900 printer. IJM provide curves (.quad files) for this system, and if there isn't one for your combination of printer / paper / ink then you can take an existing Piezo QTR curve and relinearise it. (Note that I used the term "curve" - I reserve the term "profile" for an ICC profile.) Or you can buy (rent actually) the IJM Pro tools and create your own custom Piezo curves.
I also use QTR on an OEM 3880, and for that I use the curves that are shipped with QTR. For an unsupported paper I again take an existing curve for a similar paper and relinearise. Works surprisingly well in most instances. A lot of papers have the same or similar ink-receptive coatings.
If you're using an inkset other than Piezo or OEM, then others will have to assist. It's been a long time since I created a QTR curve from first principles. I'm sure Paul Roark and Richard Boutwell will only be too happy to advocate their approaches.
---In QuadtoneRIP@yahoogroups.com, <per@...> wrote :
Thanks for the very informative answer.
So why not just use QTRGui? Well, I'd be fine doing this if I could figure out how to make a custom paper profile for QTR using my densiometer. I don't feel I have the knowledge to write a description from scratch (I don't feel like I have the knowledge or understand the process to make the ink descriptions, but I would certainly be open to learning).
However, let me ask you this: Do you think that starting from a paper profile for my printer that seems similar to the paper I am using, and then using my densiometer to redo the gray curve and then linearize is a viable method? This seems doable.