This is a picture of a phenomenon called pokies. The technical term for this unfortunate event is called bearding. It consists of bits of thread that have broken off from the top fabric of the quilt and/or batting poked through the backing in the quilting process. This is not to be confused with loopies, where the top thread tension is loose enough to allow for looping of the top thread on the backing prior to the needle returning through the fabric to the front. "Loopies" is easy to fix: just increase the top thread tension. Pokies requires some investigative work.
Now, just to clarify things, the stitching and the threads in this case are just fine. The tension is great, the stitch length is adequate and the stitching is smooth. So we have to look elsewhere. Let's start from the top: the top of the quilt, that is.
The top of this quilt is made from batiks. Batiks are tightly woven and heavily dyed fabrics. They are gorgeous, so we keep getting suckered into using them in our projects. I'm as guilty as anyone else, because I love them. But they don't love the quilting process.
Batiks require a sharp strong needle to pierce them cleanly. A Gros Beckert 20 is my needle of choice for fabrics that are hard to pierce. You blanche. Well, I'm telling you that sometimes you can get away with using an 18, but it's not as strong a needle, and I have had them break on me before when using them on quilts made from batiks. IF your customer has prewashed his or her batik fabric, you can use an 18. Otherwise, save yourself a headache and use a 20.
And DON'T use the titanium needles. They are strong, yes. But they are also flexible. This is important because that tight weave in batiks can deflect the needle and cause problems with the stitching. And, importantly, the titanium needles tend to have a slightly rounded tip, rather than the very sharp tip found in the Gros Beckerts. This rounded tip doesn't pierce the tight weave of the batik fabric and instead pulls threads from the batiks down through the batting to the backing. A dull needle can do the same thing. You can tell if you're having a problem with the tip of your needle by looking at the quilt top. If you are getting "runs" (yes, they look just like the runs in your nylons, only tiny), you need a sharper needle.
Some people find that they do much better using a smaller needle if they encounter bearding. The current wisdom about this is that the smaller the hole, the less space to drag batting through with the needle. I confess that I have never used a size 16 needle, but I do like the 18's quite a bit and prefer them over the 20's for most things.
Lastly, look at your batting. I have found that all-cotton and all-wool battings have a greater tendency to pokies than blends. Why? I don't know, but I think it has something to do with the strands of fibers and how they are aligned in these natural battings. I DO know that if you do not place the scrim side of any batting against the backing, you will definitely be more likely to pull fibers from the batting through to the backing. The scrim helps to "seal" the batting to keep stray fibers from coming through to the back.
What about the backing itself? This quilt's backing was all cotton but dyed with metallics in patterns throughout the fabric. This type of fabric may be harder for the needle to pierce, so, again, you need a strong one that won't break or deflect, but it doesn't significantly contribute to pokies. Pokies come from the inside out, and they are already on their way through the quilt sandwich to the outside by the time the backing is pierced.
How about the height of the quilt sandwich compared to the bed of the longarm? Lets say that you have rolled back to a certain spot on your quilt in order to do the next set of patterns and have forgotten to lower the take up roller to allow the quilt sandwich to rest on top of the sewing plate. Pokies aren't the issue here. Mostly what you will see is laddering and maybe loopies, because the backing isn't lying snugly on top of the sewing plate. This creats an increased distance the needle travels after having already passed through the backing before the top thread can be caught by the bobbin and looped around the bottom thread, just as the distance between these two points would be increased if you had a very thick sandwich. Only you don't. You have air between the back of the quilt and the bobbin. This distance leaves that top thread flapping in the breeze, so to speak, and you will have nests and other nasty things on the back of your quilt as a result.
Some people say that having the quilt sandwich too tight may cause pokies. This isn't necessarily so unless the sandwich is held too high by the takeup bar, as in the previous example. I have found that a tight sandwich is more likely to cause skipped stitches rather than pokies or loopies.
Now, let's talk about treatment. How to deal with pokies. Well, it's not a pretty answer. You have to pull those fibers out of your nice, neat stitching. Some quilters have used those little rotating razors that shave pills off of sweaters effectively. I pull the fibers out, one by one. If there is just a little sprinkling of fuzz, rather than full blown fibers, you can try washing the quilt. Sometimes the shrinkage that occurs with natural fiber battings will pull the whole sandwich up a little, and the fuzzies will wash away or disappear into the sandwich again. But caution: don't count on this if the fibers are over 1/4" long. You do NOT have to rip out your quilting. The stitching is fine. It's the combination of fabric, batting type, scrim placed correctly, and most importantly, having a good, sharp needle that is the cause, not your stitching.
So there's today's lesson on one of quilting's headaches: pokies -- cause, prevention and treatment, all in a nutshell.