Tuesday, September 4, 2012

Paper Piecing Basics: Log Cabin Practice Block

Machine paper foundation piecing (or MPF) is one of the best quilt piecing techniques, in my opinion. Intricate, often small scale, and varied quilt styles can be executed with accuracy and no "growing" or distortion due to cutting or stitching error. .

This tutorial includes a large number of photos for the step by step process. Once you understand this basic block, learn and experiment with other layouts in tutorials also available on this blog in the near future.

To try this block on your own, email me to request the PDF foundation to photocopy and practice with:
Jodi at hearthsewnpatterns@yahoo.com

This photo shows a block being pieced. The patchwork is joined to the backside of a trimmed photocopy. You will need one photocopy for each block you "build". Patchwork stitched will be a "reversed image" of the foundation layout. However, with a log cabin and others, it is less obvious that this is what happens.

Here is the foundation block with identification of all its parts. The seam allowance that is included is 1/4", shown as the distance between the dashed line and the outer trim line.

1. Cut out the diagram from the photocopy sheet, leaving a 1/8" margin beyond the outer solid line. The solid line is where final trim is made when block's piecing is complete.

Use scissors or rotary tools to cut.
When photocopies are from the same "batch" you may be able to cut 3-4 copies at once.

2. Pre-fold the diagram along the interior stitching lines. Use a cardboard straight edge like a bookmark, postcard, or thin plastic ruler. Note that the diagram is being folded print sides together. Place the straight edge along the line, then fold the paper over the straight edge. Be accurate. This step will help to position and visualize where the fabric needs to be placed so that it will be seamed and pressed back into its designated place.

For many styles, you can pre-cut fabric shapes. For the Log Cabin, strips work well. 
1.  To determine strip width, refer to your diagram for the finished strip plus the seam allowances plus a little excess for trim. These diagrams have two areas highlighted with red to show what would be measured (with allowances included). The seam gauge shows that the minimum strip width would be about 1 3/8". For greater ease, cut strips a little wider.

2. Select and cut a few strips to get started, then cut more as needed. The traditional log cabin block uses "lights" and "darks". The sample will be pieced with orange and violet scraps as darks. Jumble the colors, or keep the strips on the same "course" or row the same hue with different scraps.

3. The first patch is positioned in its final place - the only one that is. Cut a square patch from the selected center patch strip. Use fabric glue stick to lightly adhere BACKSIDE of patch to BACKSIDE of diagram. Creases will show you the area to cover (outlined here for understanding). Make sure the crease outline is centered under the patch.

4. Prepare to attach patch #2. This photo shows (l) the print side with area identified underneath which the joined patch will finally end up. (r) This is the backside of the diagram with patch #1 in place, area #2 outlined, for understanding.

 5. Fold the paper back along crease which falls between #1 and #2. (Crease will always be made on the target seamline, which is between the most recently added patch and the one being added.) The strip selected for #2, a light strip, is face up on the table. The outlined area is the top layer - remember this is so you can see it. Beneath the outlines of area #2 see the seam allowance of patch #1 extending beyond the fold. Position patch (outlined) area over the strip so it is "contained" within the strip.  Fabric cut end of patch #1 is aligned with end or edge of strip #2.

 6. Carefully unfold the crease without letting anything slip. Move the layers to the sewing machine (you can pin if you need to). Adjust the machine to a stitch about half your regular piecing length (or 12 stitches per inch). Stitch on the target line (crease line used in prev. step). Stitch ONLY 2 stitches before the target line starts, across exactly on the line, and ONLY 2 stitches beyond the end of the line. You will see why this is important later.

This image shows regular stitching length, left, and shortened paper foundation stitching line, right. The shortened stitches help the paper perforate along stitching lines when it is time to remove the paper from the block. Also, when paper piecing miniaturized blocks, or with very intricate designs, seam allowances are trimmed to a narrower width, such as 1/8". The shorter stitches make the seam more secure.

7. Turn foundation over. Press strip back - it will now cover area #2 (only creases identify the area from this side).

8. Place block with fabric face side down. Fold paper back one at a time along each of three creases that define area #2. Trim away excess strip #2 beyond fold leaving the 1/4" seam allowance. This photo shows a tool called "Add a 1/4" being placed at the paper fold. It has a built up ridge on the under side that catches at the fold, then provides a rotary cutting edge at the desired allowance.

 8A. This photo shows, bottom, the foundation with strip #2 extending before the fold and trim steps shown above. At top, the foundation has been turned over to show patches 1 & 2 in place.

9. This photo shows the foundation with area #3 highlighted (top), and from the backside with area #3 outlined (for understanding). 

10. Repeat the process as for patch #2. Fold diagram along along the line that separates #1/#2 and #3 being added.  Strip being added is face up on the table. Area #3 (outlined for clarity) is top layer to be easily visible, and is positioned so that it is over and "contained" within the strip. Cut edges of previously attached patches should align with cut edge of strip.

11. As before, carefully unfold, take layers without shifting to sewing machine. Stitch 2 stitches before the line, exactly on the line, 2 stitches past the end of the line.

12. Press strip #3 back.

13.  Place block fabric side face down, fold back at line defining end of #3 (where it joins to #4) and trim excess strip away 1/4" beyond fold.

13A. Repeat the fold-back process on the second  line that define area #3 to trim to 1/4" seam allowance . . 

13B. and on the third line, the same.

Each patch that is added will follow this trimming process. Find the lines that define the patch, fold back at that crease, use tools to trim.

14. Repeat the steps to add patch #4. Here you see area 4 highlighted, and the fabric side of assembly with 1-3 in place, #4 to be added outlined.

14A. Here the diagram is folded at crease between #4 and ends of #1 & #3. "Dark" strip is face up, diagram positioned over and contained within strip.

 15. Press strip back, follow 3-step trimming process. This photo shows strip #4 positioned & stitched in place, then pressed back. The LEFT image shows that each added strip begins opposite it's final position (shown by outline). When stitched and pressed back, it will cover the outlined area.

15A. Assembly here shows both #4 & #5 patches have been added to complete the "dark" or  row.

16.  Add light strips for #6 & #7, dark strips for #8 & #9.
For all strips that end  at the edge of the block, the seam will continue to the outer edge  INSTEAD of ending/starting 2 stitches from the end of the line. For this block, patches 7, 8 & 9 will have extended seamlines.

17. Make the final trim. Turn the completed block FACE DOWN on cutting mat. Place rotary straight edge along outer trim line, cut away excess paper and fabric. Repeat for all foundation edges. "Audition" layout, right, shows the neatly trimmed edges of the blocks.

18. Decide how many and complete the blocks for your project. Divide into rows, then join the blocks in the rows. This stitching is done with the REGULAR LENGTH stitching with which you normally piece. Join rows, add borders, layer, quilt, bind. 

If you do make a mistake, carefully unpick the seam from the fabric side. Try not to damage the paper foundation. If the paper separates, repair with a piece of cello tape on the front side, then continue joining and stitching in the regular way.

Here is one of my favorite Christmas miniature log cabin projects. It uses an even smaller log cabin foundation block which is also available from me as an email request. When I started this project, I was using the smaller block, 2 1/4" finished block size, to demonstrate the fun and ease of foundation piecing. Before long, I had enough blocks (16 here) to make a table mat project. Just add borders.

Once you understand the "logs" arrangement of paper foundation piecing, explore another shape in the sequence with square-in-a-square foundation piecing.

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