Pattern Decomposition

Do you remember the first time you found a critical error in a pattern?  For some of us it ranks up there to remembering where we were when 9/11 struck.

For me it happened during my second year of quilting.  I don't remember the pattern name, but I remember the quilt.  it had browns, reds and tans.  It was going to be big -- queen size.  I had reached the stage where I had gained some confidence in my piecing abilities and to be efficient I cut out the entire quilt top before I began piecing it.  Yes -- all nine yards of fabric beautifully cut up, stacked and ready for a day at my sewing machine.

I then proceeded to work through each of the steps -- before doing step two, I finished step 1 for all 20 blocks of the quilt.  I reached the point where I needed to add a large half square triangle to a previously pieced unit. I found I had to really stretch the triangle to make it fit.  Hmmm. I began checking the normal suspects:

• Did I mis-cut any pieces
• Too large of seam allowances
• Did I use the correct pieces

Everything seemed to be ok on my end.  I finally pulled out a sheet of graph paper (this was pre-Electric Quilt) and redrafted the block and checked the math using the Pythagorean theorem from high school albegra.

The Pythagorean theorem, states that the square of the hypotenuse (the side opposite the right angle) is equal to the sum of the squares of the other two sides.

The issue was not me but the cut size of those half square triangles.  I couldn't find more of the fabric so the entire quilt was delegated to the UFO (unfinished objects) bin where it languished for many years until I eventually decided to throw it and the pattern away.

Now I wish I could say this was the only time I found an error in a pattern.

I've now learned the importance of decomposing a pattern and checking the math.  This technique can be done with graph paper -- but I find I am much more efficient with Electric Quilt.

Pattern Decomposition Using EQ8

When working with Electric Quilt there are often discussions about how to take a design created in Electric Quilt and turn in into instructions (or a pattern). In Tech Know Quilters  (a membership focused on mastery of EQ8), there are a number of lessons around this very concept.

Today, let's talk about the reverse.  Have you ever purchased a pattern and then wanted to put it in EQ?  

Learn how to play detective and work from a pattern to draft the block in EQ8.  It is a great way to double check there are no math errors in your cutting instructions!

Basic Math Rules when Analyzing a Pattern for Decomposition

Rule #1 - Subtract 1/2" (.5) from length and height cutting measurements for square and rectangle units.  This also applies to folded corner units.



Rule #2 - Subtract 7/8" (.875) from length and height measurements for squares cut once on the diagonal for two half square triangles.

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Rule #3 - Subtract 1-1/4" (1.25) from length and height measurements for squares that are X-cut or cut twice on the diagonal for four triangle units.

Rule #1 Squares, Rectangles and Folded Corner Pieces

Rule #2 Half Square Triangles

Rule #3 X-Cut Triangles

The video tutorial will take you through this process using a block pattern I created back in 2005 for a BOM for a local quilt shop.

Here is the cutting chart referenced in the video.

Flower Border Block Cutting Chart

Download the block pattern including construction information here.  Here is what the block looks like in a finished quilt.

Day Garden by Kari Schell

If you try this technique, let me know how it goes.

Happy quilting.

​Kari

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