Saturday, July 28, 2012

Block assembly by "chunking"

This post is a part of the R-Burst Quiltalong.  After I get some technique explanations out of the way today, I'll be back tomorrow with the specific instructions for cutting and piecing the R-burst block.

Let me start by saying, you don't need to necessarily assemble your R-burst blocks in the way that I'm about to share.  The block is just a grid of 2" squares, and you can use whatever method makes you comfortable.  You could sew squares to squares and assemble the block in strips, or you could even use fusible interfacing or wash-away interfacing to sew up the whole block in one go. 

I do think chunking has some advantages.  You don't have to buy supplies like wash-away interfacing (yikes, that stuff is a tad pricey, isn't it??), and you don't have the extra stiffness of fusible in your quilt.  For me, I can get better accuracy this way than with row-style piecing.

So how does it work?  The idea behind chunking is to assemble in quadrants or chunks rather than in rows. As an example, let's look at a 16-patch block.  We could assemble in rows, and then sew the rows together into a block:

Row construction method:  
12 seams between squares
3 seams between rows (matching 3 seams each)

Alternatively, we could assemble in chunks, then sew the chunks together into a block:
Chunking construction method:  
8 seams between squares
6 seams between sets of 2 blocks (matching 1 seam each)
1 seam between rows (matching 3 seams) 

The number of seams and the total length of stitching is the same for both methods, but chunking makes accuracy easier because you mostly match fewer seams at a time.  The more pieces there are in your block, the larger the advantage.  With our big 81-patch (yikes) block, you really see the difference. 

Trim-as-you-go Scrap Piecing
When I'm working with scraps, I like to use a trim-as-you-go technique rather than cutting everything right at the start.  It might seem like this would take a little more time since you trim repeatedly, but you only trim each edge one time.  When you get further in the block, you are trimming multiple edges in one pass, which you can't do if you cut the pieces to size individually.  Also, overall this technique gives better accuracy.

To trim-as-you-go, start by trimming one edge each of two scraps, along the grain.  If you already have a grain-straight edge that is even, score!  No need to trim.  Sew the straightened edges together.

 As you assemble, trim only the edge that is going to be put to work for the next seam.  Use the previous seam as a guide for your ruler and cut the next edge perpendicular to the seam:
Working this way takes the pressure off when you sew because the edges of your block are always perfectly even (since you just trimmed them all in one cut!)  You don't have to try to match the edges when you start and stop; you just match your seams.  On the other hand, when you piece from perfect little squares, all of your seam allowance errors and original cutting errors add up as you go along.   If you have to trim your block during assembly, your cut squares are no longer exactly the right size.  On the other hand, when you trim as you go along, you hit the reset button each time you sew pieces together.

Once you have more than one seam, you need to make your cuts at the right position instead of just the correct angle.  Trim 2.25" from the seam parallel to where you will sew, or 1/4" more than the finished size for each square.
Make sense? 

Using Yardage
If you are assembling from strips (jelly roll or yardage) it makes more sense just to cut things to the right size from the get-go.  You also get the benefit of being able to strip piece your blocks.   If you don't want your blocks to all look identical, strip piece in sections and then mix the sections up so that each block looks different.  When you assemble, put your blocks in different orientations as well.  Once you finish, it's hard to tell that fabric A is always next to fabric B, especially if you have a lot of different fabrics in the quilt.  The quilt below is 100% strip pieced and all the blocks have identical fabric placement, they were just rotated during assembly:

You don't notice unless you are looking for it, right?  
My quilt is a mix of scraps and yardage, so I'll be combining trim-as-you-go (for scraps) and strip piecing (for the yardage) in my blocks.  It's totally fine to do that and it all works out in the end.

I'll be back tomorrow with the specific cutting & piecing instructions for these blocks.  In the meantime, any questions?

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