This tutorial describes my process for making a quilt with "floating" blocks on both sides. The quilt in my process photos is Mod Mosaic with Giant Bees. You can see more photos of that quilt, including a tutorial for my Mod Mosaic blocks, here.
Determining how to "float" blocks on a quilt top and back may seem tricky at first but, when broken into a series of simple steps, the process is pretty straightforward. This is a great way to plan a fresh modern composition that looks neither completely random nor overly labored.
How much solid fabric you'll need can vary wildly depending on the number and size of your blocks, the size of your finished quilt, and how effectively you use use your scraps. For the 60" x 72" quilt I'm about to show you, I used about 3 yards of solid fabric for each side (Kona Emerald for the top and Kona Ice Peach for the back).
When your quilt is finished, it won't be obviously which side is the front and which side is the back. We're only going to differentiate here because it's necessary to make one side (in this case the back) larger so that we can make a successful quilt sandwich. That means you're likely to use a little bit more fabric for the back.
Step 1: Mark Your Quilt's Footprint
Cut 4 pieces of twill tape or ribbon the same length as the 4 sides of your finished quilt. For example, my quilt is going to be 60" x 72", so I cut 2 pieces 60" long and 2 pieces 72" long. Tack the pieces of twill tape or ribbon to your design wall, creating a footprint for your quilt. (If you're using a floor, create a similar footprint using blue painter's tape.)
Step 2: Arrange Your Blocks
Start by dividing your blocks into 2 groups - the blocks you want to use on the quilt front and the blocks you want to use on the quilt back. For my quilt, I divided my blocks equally, selecting 9 blocks for the front and 9 blocks for the back. Because my blocks were a pretty wide range of sizes, I also made sure that each group had 1 large, 3 medium, and 5 small blocks.
Arrange the blocks for your quilt front within the footprint on your design wall. For this quilt, I placed all of the blocks away from the edges of the quilt, but you should definitely feel free to place blocks right up against the edges, like I did in the pink and red quilt shown in the slideshow above.
Step 3: Subdivide Your Quilt
Examine the placement of your blocks and consider how the areas of your quilt top can be broken down into more manageable chunks.
Start by figuring out where you can place a seam that will run all the way across the quilt top. The seam can divide the quilt horizontally or vertically, but it needs to be a straight line that runs all the way across the quilt without hitting any of the blocks. (The blocks can be right next to the seam. The seam just can't run through the middle of the blocks.)
In looking at the arrangement of my blocks, I noticed that there were 2 obvious places for a seam to run across the quilt top, which meant that I could divide my quilt top into 3 rows.
To provide another example, I'm jumping ahead to the layout of my quilt back. In this case, there was one place to put a horizontal seam. With that seam dividing the quilt back into two parts, I saw how it would be easy to further divide the quilt back into quadrants.
This is probably the trickiest step, so take your time and figure out how to best divide your quit. I recommend dividing the quilt top into either several rows of 4 quadrants, depending on what seems to work best for your layout. You may find that you need to shift your blocks slightly to find the placement for that first horizontal or vertical seam that runs all the way across your quilt.
Step 4: Fill in the Background
Now it's time to fill in the background fabric row by row, or quadrant by quadrant.
Start with one row or quadrant of your quilt top and subdivide the area (mentally or using additional twill tape and tacks) so that all of the blocks are separated. In the photograph above, you can see Row 3 of my quilt top divided into Sections A, B, and C - one for each block in the row.
Note: Subdividing so that as many blocks as possible are right on the edge of their sections will result in fewer seams and a more random-looking composition.
Select a section and consider how much fabric you'll need to fill in the background area around the block. The idea is to fill in the entire section, adding 1/4" seam allowance around the edges, so that the section can be placed back into your quilt footprint, just like a puzzle piece.
You can tackle this in a couple of ways.
The most conservative approach, fabric-wise, is to measure the precise distance from the sides of the block to the sides of the the section and cut pieces of your background fabric in those exact sizes, including 1/4" seam allowance, before sewing them to the block.
The easiest approach, construction-wise (and what I did) is to measure roughly, adding about 1" leeway on all sides. Sew the slightly larger pieces of background fabric to the block, squaring up after each addition, and square squaring up the finished section to fit back into your quilt footprint. Once again, you'll want to make sure that you've added 1/4" seam allowance to the outside of the section.
Whichever approach you choose, I recommend cutting WOF strips from your background fabric yardage and maintaining a well-organized pile of your scraps. Any time you need to add a new piece of your background fabric, check to see if there's a compatible piece in your scrap pile before cutting a new WOF strip from your yardage.
Note: Sewing the background fabric will necessarily involve removing blocks from your design wall. While the blocks are away from the wall, you may want to mark their placement with a water soluble marker or pins. (After you've finished, you can mist the marks with water to make them disappear.)
Continue filling in the background of the other sections in the row or quadrant. In the above photo, you can see my Row 3, Sections B and C.
Once you've finished all of the sections, sew them together to complete the row or quadrant.
Repeat this process to complete all of the rows or quadrants.
Step 5: Finish the Quilt Top
Sew the rows or quadrants together to complete the quilt top.
The finished quilt top should be roughly the same size as your marked footprint. (I had some cat-related interference with the bottom of my footprint, so I'll have to ask you to take my word for it that the quilt top ended up being the right size.)
Step 6: Make the Quilt Back
Arrange your quilt back blocks in the same marked footprint. Remember that, although the quilt back will be larger during construction, the finished quilt back will be the same size as the top.
Follow the instructions in Step 3 to subdivide your quilt back into rows or quadrants.
Fill in the background fabric, using the instructions from Step 4 with one important change. In order to make the quilt back large enough to make a stable quilt sandwich, fill in the background fabric in the sections bordering the edges of the quilt so that the fabric overlaps the footprint by about 3" - 4" on each side.
You can see in the photo above how the fabric in the Upper-Left Quadrant of my quilt back overlaps the footprint.
Use the same process from Steps 4 and 5 to finish your quilt back. The finished quilt back should be roughly 3" - 4" larger on all sides than your finished quilt top.
Step 7: Finish the Quilt
At this point, you should have a quilt top and back pretty much like any other, so you can just sandwich, quilt, and bind as desired!
A couple of notes about finishing these quilts:
I've gotten a lot of questions about how I choose thread for quilting when the dominant color of the tops and backs are so different. My preference with quilting is to use the same thread in the top and bobbin, and to match the lightest color in my composition (often white).
I tend to find darker thread on light fabric to be distracting - almost like someone has scribbled all over the quilt. However, I'm not bothered by light thread on dark fabric. I think it blends in just fine and, in particular, it's better for letting the composition show through the quilting.
Also, although I didn't prewash any of the fabric, I was able to wash this quilt (and quilts like it) without any problems with color bleed. I wash quilts in cool water on gentle cycle before machine drying at a low temperature. I can't guarantee that you'll have the same good results, but one of the best tips I can offer it to move a wet quilt from the washer to the dryer immediately after the wash cycle is over. Leaving a wet quilt sitting in your washing machine is one of the surest ways to cause color bleed, regardless of whether or not fabric has been prewashed.