Let's use the Sassy Sudoku quilt as an example, the second border is pieced, then attached with a partial seam. I hear someone somewhere thinking, "Why go to the extra effort of a partial seam? Why not just do normal borders?" And that's a good question.
The partial seam is actually less work and less math than a regular border. Let me explain. For the border with a partial seam, all the border strips are cut the same size (so long as the quilt is square). None of that "measure, get an average, cut, then sew the strips onto the sides, THEN measure, get an average, cut, then sew the strips to the top and bottom". You notice in the Sudoku quilt pattern, you don't have to cut your borders to a certain length. Instead, since the sides of the quilt are all the same length, and the strips were, presumably, all the same length to begin with, I suggested you cut OFF a small amount. Because I have a 36" cutting table, I find cutting off an inch or so, much easier than cutting strips to any length greater than 36". Since we were cutting 43 3/4" lengths, it just made sense. Although, it's wise to check those lengths first.
But what if the partial seam isn't in a border? What if it's in a block? The easy answer is, it's the same. However, the glaring difference, and apparent stumbling block, between adding a border to a quilt center using a partial seam, and assembling a block using partial seams, is proportions. The quilt center is proportionally large and the block center is proportionally small. But the principle is the same.
Let's make a block and demystify the partial seam.
I'm currently assembling a quilt called Intersections by Bonny Peters of Cat Den Mountain Quilts. This clever quilt was published in The Quilt Pattern Magazine as a mystery quilt over a 4 month time period. It's a great example of what you can do with partial seams.
This is what we want the finished block to look like.
Ok, so it doesn't look like anything special. Just wait until you see what it becomes when combined with it's other little friends.
The question is, how do we get there from here?
Here's a picture of the block before it is sewn.
That probably makes no sense! Weird verbal explanations, like this one, are probably the reason people think the partial seam is something mysterious.
Let's look at pictures instead.
To create the partial seam, line up the center square with the inside corner of a side unit. Bonny suggests you begin your seam as close to the unsewn seam allowance as you dare because this particular center square is so tiny (1 1/2"). Backstitch, then continue sewing to the edge. (That isn't as crucial when the center square is big because you'll have plenty of room to work the seam.) The partial seam here is sewn in black for your viewing pleasure.
Press this partial seam toward the pieced side unit. Now you can see there is a place just the right size for the second side unit to be added.
Then the third unit has a place where it fits...
... which creates a place for the fourth. Pin the first unit out of your way if it bothers you, before sewing the fourth side. Press to the pieced units after each addition.
Now it's time to close up that partial seam. I've shown this from the back so you can see that it appears exactly like a seam that has been sewn, unsewn, and is ready to be sewn again. You recognize it now, don't you?
Begin this final seam a few stitches behind the place where the partial seam ends in the middle of the piece. Backstitch, then continue sewing to close the seam. Press to the pieced unit. Press the block from the front to make it nice and flat.
That's all there is to the partial seam. EASY! It's a wonderful skill and not scary at all.
Please share photos of your partial seams on our Seamless Piecing Facebook page. I'd love to see what you are making.
If you have questions, post them in the comments or email directly RB.firstname.lastname@example.org
Don't forget to follow.
P.S. Want to see a photo of what this block becomes when paired with others like it? It's not what you expect! Stop in next week and I'll have that ready for you along with a surprise goodie.