Pythagorus and the art of Half Square Triangles
Most of you will want to skip over this... this is sleepy shutting the brain up rambling and making mental notes...
Note to self... if you lose EVERYthing else for quilting make damned sure you obtain
1. a rotary cutter which fits comfortably in your hand
2. the biggest rotary mat you have solid space to accomodate, with
3. at least an 18" rotary ruler - smaller rulers are nice, in fact if you're doing a million small blocks they'll save your wrists and half the sanity you have left, but you HAVE to have an 18" to be able to cut width-of-fabric strips to cut the smaller bits from
and
4. a 1/4" presser foot - just do it. Unless you're going to hand sew everything and are comfy with marking your seam allowance on every little piece you plan to sew, just get the presser foot whose width matches your intended seam allowance.
Half square triangles - I've run across formulae and directions for them and lost them and figured it out and lost them and refigured them out so here...
Half square triangles are nothing more than the triangles which will form a two coloured square block - thus the name. Do NOT simply sit down and cut a bunch of squares in half to sew back together! Firstly the size will be off since you'll have a seam allowance down the middle, and secondly, that seam will be all stretchy since it'll be on the bias of the fabric. I don't care who I'm making a quilt for, there's no way in hell I'm sewing a million little squares out of triangles cut on the bias and either hoping they'll come out straight (they won't, some will stretch) or using enough tissue paper to make sure they do. I will use tissue on satin, yes. Silk, yes. Rayon, probably. Tulle, almost certainly. Cotton? Oh hell no! Not picking tissue paper out of my cotton seams. Besides, all that cutting and sewing for one block is remarkably inefficient.
So let's make two at a time!
Assuming I want a 3" finished block size, which would be 3 1/2" UNfinished (with seam allowance on each side). Instead of cutting 3 1/2" strips, cut 3 7/8" strips of both colours. Cut each strip down to 3 7/8" squares. On the WRONG side of the lighter coloured fabric, take a ballpoint pen and straight edge and draw a diagonal line from corner to corner. Stack light fabric on dark, right sides together, and carefully align edges. Using that center line as the "fabric edge" to align your 1/4" presser foot to, sew along both sides of the line. Cut carefully down the line to separate your two brand new half square triangle blocks. Press them open, align the diagonal line on your rotary ruler to the diagonal seam, and trim edges to size/straighten if necessary. (Always check this - nothing gives itself away faster than diagonal seams which, well, aren't.)
Well, that's more efficient, but what if we could make FOUR at a time?
We know we want finished blocks of 3", which is UNfinished size of 3 1/2. If we could find that diagonal we could use that as the SIDE of a SQUARE, use the edges as our seams, and cut diagonally both ways making FOUR instead of two. Pythagorus says that a squared plus b squared equals c squared, so (3.5*3.5)+(3.5*3.5) or (3.5*3.5)2 =c squared... that gives us 12.25 + 12.25 = 24.5 and the square root of 24.5 is... just shy of 5, and close enough to it to be indistinguishable in fabric measurement terms. So, 5" sides if we're absolutely confident of our precision in cutting and sewing. Let's give ourselves a little wiggle room on the first set at least, and go 5.25" sides. Same basic procedure as before - cut strips, cut squares, but this time we're just going to stack light on dark with right sides together. Using the 1/4" presser foot at the fabric edge carefully sew around ALL FOUR SIDES making a closed envelope. Using the rotary ruler and rotary cutter cut carefully in half DIAGONALLY, same as before, except this time we're also going to cut each of those halves in half from corner to centerpoint. Open and press. Since we gave ourselves a little wiggle room this will require a bit of trimming to size, yet no more effort than for the checking/trimming of having made two at a time.
Dang. Math really IS in everything. ;)
Note to self... if you lose EVERYthing else for quilting make damned sure you obtain
1. a rotary cutter which fits comfortably in your hand
2. the biggest rotary mat you have solid space to accomodate, with
3. at least an 18" rotary ruler - smaller rulers are nice, in fact if you're doing a million small blocks they'll save your wrists and half the sanity you have left, but you HAVE to have an 18" to be able to cut width-of-fabric strips to cut the smaller bits from
and
4. a 1/4" presser foot - just do it. Unless you're going to hand sew everything and are comfy with marking your seam allowance on every little piece you plan to sew, just get the presser foot whose width matches your intended seam allowance.
Half square triangles - I've run across formulae and directions for them and lost them and figured it out and lost them and refigured them out so here...
Half square triangles are nothing more than the triangles which will form a two coloured square block - thus the name. Do NOT simply sit down and cut a bunch of squares in half to sew back together! Firstly the size will be off since you'll have a seam allowance down the middle, and secondly, that seam will be all stretchy since it'll be on the bias of the fabric. I don't care who I'm making a quilt for, there's no way in hell I'm sewing a million little squares out of triangles cut on the bias and either hoping they'll come out straight (they won't, some will stretch) or using enough tissue paper to make sure they do. I will use tissue on satin, yes. Silk, yes. Rayon, probably. Tulle, almost certainly. Cotton? Oh hell no! Not picking tissue paper out of my cotton seams. Besides, all that cutting and sewing for one block is remarkably inefficient.
So let's make two at a time!
Assuming I want a 3" finished block size, which would be 3 1/2" UNfinished (with seam allowance on each side). Instead of cutting 3 1/2" strips, cut 3 7/8" strips of both colours. Cut each strip down to 3 7/8" squares. On the WRONG side of the lighter coloured fabric, take a ballpoint pen and straight edge and draw a diagonal line from corner to corner. Stack light fabric on dark, right sides together, and carefully align edges. Using that center line as the "fabric edge" to align your 1/4" presser foot to, sew along both sides of the line. Cut carefully down the line to separate your two brand new half square triangle blocks. Press them open, align the diagonal line on your rotary ruler to the diagonal seam, and trim edges to size/straighten if necessary. (Always check this - nothing gives itself away faster than diagonal seams which, well, aren't.)
Well, that's more efficient, but what if we could make FOUR at a time?
We know we want finished blocks of 3", which is UNfinished size of 3 1/2. If we could find that diagonal we could use that as the SIDE of a SQUARE, use the edges as our seams, and cut diagonally both ways making FOUR instead of two. Pythagorus says that a squared plus b squared equals c squared, so (3.5*3.5)+(3.5*3.5) or (3.5*3.5)2 =c squared... that gives us 12.25 + 12.25 = 24.5 and the square root of 24.5 is... just shy of 5, and close enough to it to be indistinguishable in fabric measurement terms. So, 5" sides if we're absolutely confident of our precision in cutting and sewing. Let's give ourselves a little wiggle room on the first set at least, and go 5.25" sides. Same basic procedure as before - cut strips, cut squares, but this time we're just going to stack light on dark with right sides together. Using the 1/4" presser foot at the fabric edge carefully sew around ALL FOUR SIDES making a closed envelope. Using the rotary ruler and rotary cutter cut carefully in half DIAGONALLY, same as before, except this time we're also going to cut each of those halves in half from corner to centerpoint. Open and press. Since we gave ourselves a little wiggle room this will require a bit of trimming to size, yet no more effort than for the checking/trimming of having made two at a time.
Dang. Math really IS in everything. ;)