With a little know-how, fixing a broken warp end is a relatively easy fix. To do this, you need to incorporate a supplemental warp yarn. Over the years my thinking has evolved on how to do this. The fundamentals haven’t changed, but how I manage the overlap has.
To fix a broken warp end, gather the following materials: a small tin or lidded bottle, mint tins and pill bottles work well; small weights, such as pennies or small bits of hardware; a tapestry needle; a t-pin or something similar; and a piece of warp yarn the same length as your warp. Even if you have already woven a considerable amount of cloth, you want to cut a piece of yarn the same length as your warp, loom waste and all.
Start by leaving the tail of the broken end in place in the cloth you have already woven. Remove the other end from the heddle and toss it over the back beam.
Thread the tail of the warp yarn on a tapestry needle and bring it through the slot or hole where the broken end was threaded, then needleweave it into the cloth following the path that the broken end is taking.
Pull through a length of yarn equal to the length of warp that you have already woven, plus your desired fringe length. Wind a portion of the tail on the head of the pin. Secure the t-pin in the cloth so the head lines up about where the broken end is. It doesn’t have to be in exact alignment.
The break in this example is fairly close to the start of the cloth. Your tail may be longer if your break is further along in the process. (Becaue this break happened so close to the start of my cloth, I could needleweave the supplemental yarn all the way back to the apron rod and tie it on, but for the sake of a general overview, I’ll carry through this example as I would if the break happened further along.)
Wind the remaining length of warp into a small coil and place it in the container with the weights, leaving about 20’’ hanging free.
Once the tail is secure, hang the tin off the back of the loom to weight the supplementary end. If the end has too much or two little tension, you can add or remove the weights.
Continue weaving. As you advance the warp, remove extra warp length from the tin and reposition. Remove the t-pin before it is wound onto the cloth beam. If you have a particularly long tail, be mindful that it doesn’t snag as you wind onto the front beam and skew your cloth.
How you manage the overlap between the old yarn and the new is where some of my thinking has evolved. You can snip the ends to leave some overlap as you would a weft join. Depending on the placement of the join, the thickness of the yarn, and the weave structure, it may or may not be noticeable. If the yarns are bouncy and thick or fall in a particularly visible part of the cloth, I may reverse engineer a ply-split join to smooth out and secure the overlap.
Here is a third option that leaves no overlap and why you are leaving such a generous tail on your supplementary yarn. Once the cloth is off the loom, remove the length of broken warp yarn still in the cloth (upper middle), and needleweave the supplemental yarn tail in its place (far right). This creates an uninterrupted warp end from one end of the cloth to the other. This process is a bit tricky in structures other than plain weave. You can use another end in the cloth that follows a similar path as your road map.