How do you Join Batting
 

I want to use (don't shoot me) poly high loft batting for a very large queen size quilt. The problem is I only have it half the width I need...Question, can you piece it and how do You piece, if you do? would I piece it when join goes right down the middle from top to bottom? or Do I use the whole width in the center and make two joins on each side?

I searched online but wanted real advice from people who have tried already. This quilt is not for show, for everyday use.​

Just thinking that I would use that iron on tape on both sides of the batting. On cotton batt I would just zigzag. But poly would get flattened. Probably cover with a pressing cloth and lower temp to prevent melting. I don’t think where you piece would matter

Join together by hand with a whip stitch. Don't press it.

Anytime you piece a back or a batting you want to avoid being right on the typical folding line. That's the reason you usually piece a back as a full width in the middle and the sides as a half width. Just offset the join as much as you can, even if that is just 6 inches from center that is enough.

I've pieced batting before and typically I prefer a fluffier loft than is currently popular. I simply butt the pieces together and using a large stitch handsew a wide zigzag about an inch in from either edge along the length of the join. Don't pull too tight and be careful when you pick it up and move it. Best to pretty much have it in position to place your backing, if you are using spray baste once it is joined to the back it will be fine to flip around and place the top and it should hold just fine during the quilting process. You might want to add a few safety pins around the seam for extra security.

I haven't had to piece batting with a long arm. Don't see any real problem, just be gentle loading and pulling.

PS: I always fluff my batts in the dryer for a bit before using them, get as many wrinkles and such out before they become a problem.

I have pieced many poly batting strips. I use a ladder type stitch, usually large stitches. I FMQ the quilt and no one would be the wiser. Years ago I pieced three or four larger quilts and no one could tell. I never iron poly batting and that is the most of my battings.

We were taught at a quilting class to use the Wave cut with both pieces together as you cut the Wave, then move apart and then push back together and Hand Stitch a Big stitch to hold it together. It works but a lot of time is used up if you are in a hurry.

I place two pieces of batting side by side- not overlapping just up against each other then using a wide- long zigzag stitch I stitch the two pieces together. This has worked for me for 20+ years. It’s quick and I can piece as many pieces as I need to in order to reach the size I need. It does not show at all in the quilt. You can not tell once the quilt is quilted that the batting was not a whole piece

This is how I now join batting too (after trying the wavy line and hand stitching and iron-on tape), but I'm not sure how easy it would be to zigzag high loft batting pieces together, because I've never tried it. My first thought would be to try the zigzag, and if that is difficult because of the loft, then stitch together by hand. I quilt fairly densely by longarm, so I don't worry at all about where the batting joins fall.

I use the iron on tape when joining batting very successfully but never use the poly batting. No help for you from me.