I wash everything before I sew it. I have been glad I did...several times!

I used to be an assistant manager at a House of Fabrics before they closed their doors, let me tell you, the formaldehyde was so strong that it took me a couple of weeks of nose bleeds to get used to it, so I fully understand the need to wash in that case. But, did you know that starch attracts bugs? Here is a snip from an article on e-quilter .com

Ever since reading Robbie Fanning's book on machine quilting, I starch the living daylights out of my fabric, to whit: I iron the prewashed stuff with heavy starch just before cutting (don't leave it folded after starching or you will get a very difficult to remove wrinkle or crease) Then I starch each time I press any seam. It gives a really fine, crisp line and by halfway through the texture of the quilt top is like card stock. If you're doing any embroidery or applique, it is much easier--almost a built in stabilizer. However, something Robbie does not caution but is essential for anyone hoping to preserve their quilts--when you're done making the quilt, you MUST wash out the starch--silver fish just love starch (and I'll bet it's tasty for other creepy crawlies too) Don't leave starch in anything stored--also includes heirloom-sewn kids clothes which often are starched heavily as part of the lace attaching process.

I too, love to use the starch on prewashed fabrics, but only use the starch on a current project, not fabric that you will be storing. Starch can also cause discolorations after time, so just be careful when you use starch.

pros and cons I see coming to lite:

If you wash, you must starch, but bugs love starch...

Unwashed gives a nice crinkled effect after washing the finished quilt

Washed then starched gives a wonderful 'flat' finish to your work

Unwashed can run colors, but so can washed

Unwashed you must handle with care in the steam from the iron as it will shrink unevenly, so a dry iron must be used.

Formaldehyde is a nasty chemical!! No getting around that one.

Starch can cause discolorations and make creases and wrinkles permanent.

I guess it comes down to this. Treat your fabric as it would be treated in the end. In my case, I make quilts to be used, hens, washed again and again. I like the crinkled look, so I don't wash before but wash the hello out of it before it is used.

Agree whole heartedly with the above.

This is what I do. I cut a small piece, couple of inches or so, and wet it down and rub it on a piece of white fabric. If color comes off I wash, if not I don't worry about it. I've only had a hand full of fabrics over the years that have run.

Batik users should do this for all batiks. Some run pretty bad. Just my opinion. :)

I just learned a lesson on washing.. I missed washing a fabric in ddil's king size quilt she was just given. My son put it in the dryer to freshen and get folds out of it, applied a little steam to help and one color ran all over white dashing around that block. Thank goodness I used it for just one block so the whole quilt was not ruined, happened to be on the bed over hang. But backing was ruined.

I haven't pre-washed for over 20 years...and don't plan on going back to it...love working with the fabrics that still have their finishes in them...they sew so much better. I have never had a problem with bleeding...but...I only wash quilts later in warm water...never hot, and I never leave a wet quilt just sitting, always am right there to get the quilt to the rinse cycle, rinse several times, then spin and either lay flat to dry, or hang outside with a sheet over to protect the quilt, and some quilts I will throw in the dryer at least for part of the drying time.

it depends---some fabrics come through the door and straight into the washer-some don't get washed until the quilt is complete-
just like everything else with quilting- every project is it's own- has it's own (feel) (personality) needs and requirements- each is treated as an individual -- some need to be prewashed- some do not --
sometimes i am concerned about a fabric shrinking differently- sometimes the fabric has a funky smell- or feel to it-
sometimes it has (old-set in) creases- washing helps remove them-
if it's flannel i prewash unless it's for a raggy quilt- if it's batik or a hand dye i always prewash-
if its pre-cuts i do not pre-wash. it all depends on the project and fabrics---there is no right or wrong- and no reason for people to get all freaked out about it-
for 30 years i made clothes for my siblings, children, grandchildren- costumes- lots of different items- never once did i pre-wash any fabric i used---i never had an item shrink, run or fall apart because of it...it's only been since quilting that the whole (issue) has come up- before that i never even thought about it.

I just did a DP9 without washing and I felt like such a rebel. lol

I prewash everything, primarily to remove the chemicals, finishes, and crud. Most of what I currently do is fused and the web will not adhere to unwashed fabric.

I don't know what kind of fusible you use but Wonder Under sticks just fine to unwashed fabric. I have used up yards and yards of Wonder Under on unwashed fabric and haven't had a problem yet.