Some Thoughts on Perfect Piecing
Well, maybe not perfect, but better than we often do...
Up until the time when I am writing this, Treadle On block exchanges (TOBE's) have pretty much emphasize very simple blocks that could be deliberately made oversize and then trimmed down to our standard dimension of 6 1/2". (Or on a few occassions 9 1/2"). That meant that everyone could use whatever techiques of sewing they were used to and all the blocks would still go together. This is possible when the blocks feature a purely rectangular structure. However, when a part of the block features points, things get tricky. Unless the piecing is pretty precise, joined blocks can cut off the tips of points, making it visually clear that something isn't quite right. Our next TOBE features the Bird in the Air block. In truth, this is still a simple block, being in it's basic form a simple four patch. However, three of the four elements are half square triangles (HST's) and unless all of the blocks are pretty precise, cut off point tips are going to be a problem.
It's no secret that I am a fast and not terribly precise piecer. That's certainly why I generally favor trimmable blocks. I like to make blocks oversize and trim them, thus knowing that the next step, joining the blocks, is starting off from a good beginning. The BITA block exchange is going to force me, as well as the other participants, to be more careful, and to learn better piecing techniques. Hence, I thought I would do some practicing and share some experience and thoughts that may help.
Variable 1:
First, you have to understand and accept that measuring, at the level we generally do it, is not a precise lab science. There are many variables, and all can affect your finished product. As an exercise, round up a bunch of rulers, from a wooden yard stick to cloth and steel tape measures, to the standard plastic quilting rulers and guides that you use. Carefully compare the inch measurements. Don't be surprised if they are not precisely the same. I learned long ago in even rough wood working not to use several different tape measure to measure boards for a project. Look at the lines on the rulers. Some will be very fine, some will be thick. Obviously, with a thick line, you can have more variation than with a thin one. If you are fortunate enough to have one around, compare your usual rulers to a stell machinist's ruler. There's quite a difference. On some of our plastic rulers, they could never even fit in enough lines for precision measurement to 1/32", let alone 1/64".
When cutting with quilting rulers, you are going to have to use your eyes, which are actually quite accurate instruments, to achieve consistency. Always cut the same, i.e. to the center of a wide mark, for accuracy. You can also use these wide marks to your benefit in some circumstances. Let's say you cut and sew a practice block, and it comes out undersized. Try another one, but cut to the side of the mark that will give you just a tiny bit more fabric, and sew another test block. It's a variable that you can use, with care. Obviously, the reverse is also true. If your test block comes out oversized, you can try another test block, or batch, cutting the the side of the mark that will give you slightly less fabric. Yes, it's getting fussy about things, but with practice it gets easy.
Consider all your rulers... some, the Olfa's that I like so much, with the clear yellow markings, are wide marked. Others, like the Olipfa's, have finer, black markings. These are not as easy for me to see and work with quickly, but are more precise. For a finicky block, I'd probably start by using that type of ruler.
Summary... study your rulers, practice cutting with them. Make sample or test block runs before really starting your project.
Variable 2:
Just as your rulers can vary, so can your sewing machine feet or markers. No two 1/4" piecing feet are necessarily the same. Even a given foot can vary from machine to machine. This is due to differences in the needle setting, differences in how the foot attaches or fits to the foot bar, differences in the feed dogs and most of all, differences in how you see the foot. Does it have a sharp edge or a gentle one? What is its shape? Is it a solid 1/4" all down one side, or does it have a 1/8" projection from ;the 1/4" section, for miniature quilt piecing? All of these affect how your eye sees it.
Another really big factor is your light. All feet cast a bit of a shadow. Where and how does it fall? That will affect how your eye sees it. I have eye problems. I use a lot of light, usually two goose neck lights, clamped on either side of the treadle table, with one pointing at each edge of the foot... and I usualy have them positioned close to the foot. I'm trying to eliminate any foot shadow so I can really see and relate the edge of the fabric to the edge of the foot.
Again, it's really important that you sew test seams. Sew and measure, sew and measure. Use the finest ruler you have and keep at it till you have the truest 1/4" seam you can get.
Variable 3:
The seam itself is maybe the biggest variable. How straight do you sew? Here's an exercise for you. Take a piece of white fabric and draw some fine pencil lines on it. Practice sewing on the line, trying to stay dead center. How well did you do? Once you can do that well, practice sewing just to the right of the some lines, just to the left of others. Sooner or later, you will encounter someone's instructions that advise you to sew a "scant 1/4", i.e. just the tiniest bit thin, or less than a true 1/4". You need to know that you can do it, maybe by eyeballing your fabric into the foot shadow a trifle, or past its edge, or whatever works for you. As above, lets say you have everything set up the way you want it, and working well, but your test blocks come out a bit undersized; you can compensate by sewing a scant 1/4", which will leave a tiny bit more fabric inside the block. Conversely, say your test blocks come out a bit oversized, you can compensate by sewing a "heavy 1/4", which will use up a bit more of the fabric within the block. You're in charge... figure out what you need to do to get the perfect block you want, and then make sure that you are able to do it.
Variable 4:
Something else to pay attention to is the needle itself. A thin needle will give you a finer, more precise seam than a thicker one. I use a 10 or 11. I'd use a 9, but frankly, I can't see to thread one. On many of the old machines, only the larger needle sizes are readilyl available, often a 14. If that's your situation, again, make test blocks and be sure you are getting what you want.
Above all, with needles, stay sharp! A dull needle can't sew a good seam. A really dull needle will break threads in the material. Most of us do not change needles often enough. A large project should use several needles. Whenever a needle hits the needle plate, change it immediately; its point will have been flattened. I have stood over people sewing and been able to hear that their needle was dull. I could hear it "pock, pock, pocking" as it punched through the fabric. Aside from damage to the fabric, a dull needle causes puckering. In turn, puckering causes the blocks to come out short vertically. You might end up with a perfect seam and the blocks measuring right on across, but find they are short on the up and down measurement.
Variable 5:
The fabric itself affects finished block size. Try sewing on a brand new piece of unwashed, good quality cotton print. You should have pretty good control. Now try sewing on a piece of real thin, well worn, many times washed cotton handkerchief or blouse material. It tends to depress a bit with the needle (especially if the needle isn't sharp) and is harder to steer. While there are a f ew folks who like to sew with unwashed material, most of us follow the old rule of washing all fabric before the project, in case there is any shrinkage. Obviously, that softens it. The solution is to starch it, using whatever brand or type of starch you prefer... either int he washing machine or spray on as you iron it. The starching stiffens the fabric and make the sewing smoother. One word of caution... don't store starched fabric for too long, bugs like starch! If you finish a top with material that you have starched and are going to store it as a UFO for a long time (No, none of us would do that, would we?), store it in sealed plastic bags.
Variable 6:
Your tension settings can be really critical for getting perfect blocks. Improper tension causes puckering...see notes re puckering due to dull needles, above. Here again, your practice blocks and seams can show you how you're doing. I like to use the minimum tension that will let the machine handle the feed, including doubled seams. Since I don't use reverse (even when I have it) but prefer to drag tack, this works well for me. I can just increase my hand pressure on the fabric and stop the feed for three stitches and the seam is locked. Heavy tension increases any tendency to pucker. Something to bear in mind is that you can have a perfect stitch, but with a lot more tension than you need. A perfect stitch is the result of evenly balance tension, not necessarily correct tension. In addition to causing puckering, heavy tension increases the likelyhood of "fabric creep", i.e. the top and bottom layers don'e move evenly together. You start out with two identically cut 6 1/2" squared, but afte sewing them together, they don't line up on the bottom... not good. Heavy tension also makes it harder to pull the finished work out of the machine, often warping or pulling the last stitches made.
The Horrifying Truth About Variables:
Now that I have told you about all these variables, I'll tell you the worst thing about them, as they apply to quilt blocks... the are cumulative! We are doing the simple BITA block as a four patch. That means that there is only one seam vertically and one seam horizontally in the finished block. That's why I can still say, in spite of its having points, that it is really a simple block. Picture a Nine Patch... two seams vertically and two seams horizontally. Let's say you are producing seams that are 1/16" off... your finished block is going to be a full 1/8" off. The more seams, the more the imperfections gang up on you. To repeat something I have already repeated several times, your protection is to learn your machine and rulers, make test blocks, and practice enough to be confident of the outcome before you set out to make a run of 40 blocks.
OK, I've dumped a lot of information on you. It almost makes it sound impossible, doesn't it? It's not. It's just a matter of doing some serious practicing and learning your machine and rulers.
Pleasant piecing!
Captain Dick