Problems with Plaid
I tried weaving a plaid throw in plain weave, using a 6/2 worsted-wool yarn. As it was 16 wraps to the inch, I used an 8-dent reed and sleyed 1/dent for plain weave. The warp stripes did not show through and were completely covered by the weft. I tried 10 (similar result) and then 12 ends per inch. I could see the plaid in the fabric with the warp sett of 12 ends per inch, but the fabric was very stiff. Please tell me where I am going wrong.
We can give fairly straightforward standard recommendations for setts in cottons and linens that will produce a balanced plain weave (i.e., picks per inch equal ends per inch). For a plaid to show, the weave definitely needs to be balanced, whether in plain weave or twill (as for tartans). How to achieve a balanced plain weave is much harder to pinpoint with wool than with cottons or linens. The actual yarn, the desired hand of the fabric, and the degree of wet-finishing are all variables that don't lend themselves to standard setts. Wool yarns, depending on the type of wool, the spin, the number of plies, and their general loftiness, can be very different in thickness, softness, and behavior during wet-finishing. Sampling is critical.
I am guessing that you beat the weft in too firmly with the sett of 8 ends per inch but got a balanced weave with the sett of 12 ends per inch. The latter sett made it easy to achieve the balanced plain weave because the yarn itself allowed that weft sett with a comfortable weaving rhythm. However, your finished fabric would have had the right hand (I'm guessing) if you had worked hard to place (not beat) 8 picks per inch with your 8-ends-per-inch warp sett. You would have to wet-finish that fabric to know for sure.
Wet-finishing wool is tricky in that the degree of fulling (to the exact feel you want for a soft, warm throw) is a question of the amount of agitation. If you have a top-loading washer, you would check every two minutes after the first five minutes of agitation, stopping the process when the fulling is almost exactly where you want it (then completing the cycle to spin out the water). This is harder to do with a front loader. I'd probably start it there with five minutes agitation and then finish it in a washtub by hand (hard work). Whatever it takes to wet-finish a small sample will be harder to do with a large piece, but worth the time and effort (both for trying the finishing process with a small sample first and for completing the process with a large piece by hand if necessary). I haven't tried fulling with a front loader, and since these are becoming the standard washing machines sold, I treat my top loader with careful respect.