So what is the difference in coated paper stock?

Coated papers come in two flavors: woodfree and mechanical. 

Woodfree papers (also called freesheets) are made from wood but do not contain wood. The wood is chemically treated to release lignin and produce pulp that is nearly pure cellulose.

Lignin is essentially the glue that holds the cellulose fibers together in the tree.  It is dark and gives paper opacity but does not add strength and makes the paper less white.

Mechanical (or ground wood) papers are made by mechanically grinding the wood to produce pulp.  In mechanical pulps, the lignin remains, and the wood is still wood.

Traditionally, coated papers have been classified as Premium, #1, #2, #3, #4, and #5. Over the years, the differences have blurred, but nevertheless, there is a range of qualities and prices.  Higher quality papers have higher prices, of course, and often have a heavier coating, better print surface, and higher brightness.

The Premium and #1 coated papers are all freesheets and are typically used for high-end jobs where quality is paramount. Short-run, high-end jobs on high-quality papers can be cost-effective and deliver good results. Premium and #1 coated papers are mostly printed sheetfed because of users’ quality and run length requirements.

The lines get blurred with #2, #3, and #4. The #2s are freesheet, as are most of the #3s, while #4s are mostly mechanical and the #5s are entirely mechanical. The #2 and #3 coated freesheet papers have improved in quality over the years and produce excellent graphics. Because they have lower prices than the #1s, they are typically used for longer runs. As a result, as you move from #2 to #3 then #4, the percentage of web printing increases.

Because of their opacity and low cost, the #4s and #5s are commonly used for long-run jobs, like magazines, catalogs, and retail inserts.  These papers are also sometimes called lightweight coated (LC).

To add to the confusion, the #5s also compete with supercalendered papers or SC. Supercalendered papers are uncoated papers that are “polished” in a stack of heavy metal rollers, called a “calender,” to give a glossy appearance similar to coated papers.

Now you know why we say, coated papers come in a variety of flavors. Different mills participate in different categories. Imports play a role in some segments, but not others. As a result, the pricing dynamics can vary from grade to grade. One thing remains clear: prices are determined by supply and demand, not demand alone nor supply alone.