So I ran out of the new supplemental warp.
I got three dishcloths out of it.
But there was still some base warp on the Jane loom. So I took another batch of thrums from the collection and tied a new supplemental warp to the ends of the old one so I could draw it through the heddles rather than rethreading them. This was a bit fussy, but relatively quick since it didn’t involve many warp ends. My main concern was the knots coming undone as I drew them through the heddles. I looked around for some kind of fabric stiffener or glue and found the spray bottle of starch I’d bought for stabilising quilt tops. It did the trick, and I’m now weaving dishcloths with two shades of mid-blue patterning.
Using up thrums and adding new colours is making these dishcloths interesting to weave, but I am looking forward to getting the loom cleared. Especially because I found a tutorial for zokin (dishcloths made from old fabric stitched with sashiko) which, while all done by hand and so not particularly fast, are probably a LOT faster to make than weaving (and sewing) them. And will be an excellent way to use up scrap fabric and yet more thrums.