Prism99

Starch can help improve accuracy. I usually do not prewash fabric, which means there are still stabilizers in the fabric when I cut. Recently I made a square-in-a-square pattern which meant sewing a lot of bias edges. It came out okay (mostly because I cut the pieces with my Accuquilt Go, so the cutting was very accurate), but if I make this pattern again I will definitely do a heavy pre-starch to help stabilize all those bias edges more. When I do prewash fabric, I starch it heavily before cutting because all the commercial stabilizers have been removed.

Starching is a personal choice. Heavy starching before cutting stabilizes fabric so the cuts are more accurate and so the edges don't stretch or distort from sewing and handling. In addition to this (or instead of this), you can also spray starch as you go. I typically spray starch blocks as they are completed. Usually I press the blocks first, then spray starch and press again. It helps make the block lie flat and keep its shape when handling. I also spray starch the finished top once it is on my midarm frame. (At that point, I don't iron; just spray starch. Sharon Schamber does this and has a video on Youtube showing how she sprays and rolls.)

Mary Ellen's is a nice product, but it does not provide the heavy starching I am talking about.

For heavy starching, it's easiest for me to use Sta-Flo liquid laundry starch diluted in water. A 1:1 starch:water solution is the dilution that I use on yardage, although a 1:2 dilution would probably work well too. My method is a little different from some of those above, as I have found the repetitive use of a spray bottle is hard on my hand. I prepare the starch and water, place my yardage on my kitchen island, and use a large polyester wall painting brush (about $4 at Walmart) to apply the starch. I saturate both sides of the fabric, wait a few minutes to make sure the fibers have had a chance to absorb the starch (it has a tendency to lay on top of the fabric for awhile, especially if the fabric has not been prewashed), then toss in the dryer. You could take it out while damp, but I usually let it dry completely in the dryer. It's easiest to iron with steam, as steam re-activates the starch where you are ironing. I have given up trying to use steam because our water seems to destroy irons, so this is where I use a spray bottle to slightly dampen the fabric as I go. Fabrics vary in how stiff they get, but I aim for almost cardstock stiffness. (Many fabrics do not get that stiff.) I actually iron the yardage, as it is considerably faster and more satisfying than pressing. I can get away with ironing because the starch stabilizes the fabric and makes it much harder to distort while ironing. I do try to use a reasonable touch and a nice smooth iron surface. The yardage comes out fine for me this way.

After the above starching process, I am ready to cut and sew. Starching makes the cuts more accurate and also helps prevent edges from distorting as I sew. I should mention that using a good quality fine cotton thread also helps accuracy. When I switched from Mettler 50/3 to Aurifil 50/2, my piecing accuracy improved considerably.

It is when pressing blocks that I pay a lot of attention to pressing instead of ironing. I press the seam before turning it, although again this is a totally personal thing. It does seem to make the thread sink into the fabric. I probably pay the most attention to pressing the seam fold carefully. After that is done, I am careful to only press, not iron the block. Once ironed, I usually will give the block a light spray starching and iron again.

One thing to be aware of is that starch can scorch if it is lying on top of the fabric and has not been thoroughly absorbed into the fibers. That scorching comes out in the wash, but can be disconcerting. This is why I am careful when using spray starch. Sometimes I can mist the block with spray starch and press immediately, but often I will give it at least a few seconds to be absorbed into the fabric. If I spray starch heavily, I try to give it at least a minute. If I am in a hurry, sometimes I will spray starch the wrong side then turn the block over to press from the top.

The variety of ways to starch shows that there is not necessarily a right or wrong way. The way that works for you is the right way for you!

I will say that I never use Best Press. I tried it, but for me it does not provide enough stabilization to make it worthwhile. When using spray starch, I purchase the best quality I can find at Walmart (currently Faultless Premium professional), as my impression has been that the cheaper versions often don't absorb as fast into the fabric. As far as I know, Sta-Flo does not have any fragrance added to it. I have never tried to use it in a spray bottle because I try to minimize how much spraying my hand has to do (the commercial cans require only pressing a button). If you use Sta-Flo in a spray bottle, you must dilute it much more than 1:1 as that would be too heavy to spray I think.

Hope this helps! Edit: Sorry to ramble on so long......