I just downloaded the new towel eBook (Top Ten Dish Towels on Four Shafts) and have a question about yarns. It looks like several of the projects use 10/2 pearl cotton while others use 8/2 unmercerized cotton. I have a lot of 10/2 pearl cotton on hand and wonder if I can use it instead of 8/2 cotton in some of the projects. Would I need to change the sett? Also, I've heard that pearl (i.e., mercerized) cotton is not as absorbent as unmercerized cotton. Is that true and would that make pearl cottons not work well for towels?
Your question is an especially good one. Since the projects in the eBooks contain articles published throughout Handwoven's history, many of them were woven in yarns that are no longer available. In those cases, we update projects in the eBooks to recommend yarns that are currently available and usually point out that these are substitutions for the originals. One yarn that has been lost over the years (sadly) is 10/2 unmercerized cotton in colors. For projects that used this yarn, we usually recommend 10/2 pearl cotton. Unfortunately it is true that unmercerized cottons are more absorbent than pearl cottons. (Industrial texts claim the opposite, but my guess is that pearl cottons absorb dyes better than unmercerized cottons and that is the reason the absorbency claim is made.) I have found, though, that over time, repeated washings improve the absorbency of pearl cottons.
However, if your biggest goal is absorbency (if you are actually going to USE your towels instead of display them), you can easily substitute 8/2 unmercerized cotton or 22/2 cottolin for any project calling for 10/2 cotton, whether unmercerized or pearl. Consider the towels in the eBook by Norma Smayda (Three-Shaft Summer and Winter, pages 23–25). The original towels were woven in 10/2 unmercerized cotton. If you examine the photo, you can see that the towels look unmercerized—they actually LOOK absorbent. To substitute 8/2 for 10/2 in this project, simply change the sett to 20 ends per inch instead of the original 24 (also use this sett for any plain weave or lace weave fabrics in 8/2). For twills, change the sett so it is from 4 to 5 ends more open (28 to 24, for example). You can also substitute 22/2 cottolin for 10/2 in the same way as 8/2, making the same changes to sett. Note that making these changes in sett will produce a wider fabric than the original, so you may need to adjust the number of warp threads if you want to achieve the same width.
In a subsequent discussion about her towels, Norma Smayda said that she would recommend 16/2 unmercerized cotton, which IS available, as a substitution for 10/2 unmercerized cotton, 16/2 cotton would work well with a sett of 30 ends per inch for her summer-and-winter project (and for plain weave and lace weaves). To achieve a similar width to Norma's towels with 16/2 cotton, you'd need to add one repeat to the warp color order (108 ends per repeat for 412 total ends).