Modern day hand quilters or even domestic machine quilters generally baste the three layers of the quilt sandwich together - top, batting, and backing. But when having your quilt professionally done on a longarm machine the parts and pieces need to come separately because they are loaded separately. In some ways the set up reminds me of the frame my grandmother had that was lowered down from the ceiling - the entire quilt was stretched out...see if you agree with the similarity.
It is very important that the back be larger, as mentioned, than the top. Nothing worse than running out of back before you run out of quilt -- ask me how I know! Not only does it need to be long enough, but there should be enough clearance on the sides to avoid hitting the clamps that are used to keep the sandwich taunt during quilting. Not fun to bump into these babies, leaves all sorts of goofy boo-boos in the quilt design. It's equally important that the back be square and lay flat just like the quilt top (for more on this visit my website). If it can't be loaded square, it won't quilt square or be pucker free. Again, ask me how I know!
The back is pinned on to the leader bars (or takeup rollers) of the longarm - at the top and bottom forming a tight hammock of sorts. If the back isn't square it will sag (not good).
The pinning process takes up several inches so this is why your quilter asks for the back to be larger. Depending upon the density of the quilting, the way it is rolled, and a few other unknown factors this is another reason that the back needs to be longer. Trust me, it really truly isn't fun to run out of back before you run out of quilt. Your quilter should always measure your back as well as your top to make sure everything will work properly.
After the back is pinned top and bottom, with the excess backing rolled onto the bottom leader, the batting is then stitched on to the back. I use a straight stitch to do this.
One, it gives me a straight line to be able to line up and baste the top on, and two it allows me to pretest the thread tension before taking a stitch on the quilt top.
Next the pieced top is basted across the top and down the exposed sides. This basting process continues as the quilt is advanced helping to keep the top square and smooth.
Depending upon your quilter, the bottom of the quilt top can either be pinned and rolled up on another leader bar or it can simply "float". I prefer to float my tops, so they are gently tucked under the machine out of the way as I work.
This process generally takes no less than 45 minutes of preparation, obviously larger quilts take longer to pin or "load" than baby or lap quilts.
If the quilter is doing a "panto" ~ which is simply a designer paper pattern followed by a laser light ~ he or she is quilting from the back side of the machine. (Unless of course it's computer guided instead of hand guided, but I know nothing on that subject).
Working on the back side can have some disadvantages, especially if the quilt top has "issues" or doesn't lay flat - the quilter isn't looking directly at the quilt at all times, just glancing up as he/she is following the pattern. Generally this is not a problem - however, some quilts require a little TLC and the quilter may suggest that a panto would not be in the best interest of the quilting process.
Once a row has been completed it is time to "advance the quilt" to be able to quilt the next row. The pattern is lined up with the laser light as the take up leaders are rolled exposing more of the quilt top. The exposed sides are basted down (from the front of the machine by the way) and then the next row is quilted.
This process is repeated until the end of the quilt is exposed - at that time the bottom of the quilt must also be basted to keep from flipping up and being caught in the hopping foot and to generally just keep it in place for the remainder of the quilting process.
Seems simple. In a way it is. However, please understand that following a line with a laser light does take some coordination to flow smoothly...and then there's all the issues of making sure the tension is correct not only with the thread but with the quilt sandwich itself. Longarm quilters all go through the school of hard knocks to learn their craft and maintenance their machines. Many only do pantos while others don't do them at all. Freestyle quilting moves from the back of the machine to working from the front of the machine, as does freehand custom or even heirloom design. There is never one way to quilt a quilt. There are always options. Everyone has their own personal style and their own personality. It's truly a partnership in completing a quilt between the piecer and the quilter. That's what I enjoy about my job. Building relationships with my customers and having the honor to work on such beautiful pieces of art!
This particular quilt has a few more rows to go...and then it's on to a custom quilt...perhaps I'll share photos of that process too.