Just a note on prewashing fabrics...

I've read a lot of opinions about whether or not fabrics should be washed before using them in a project. I have to admit that I don't usually prewash new fabrics. I do, however, wash all the reclaimed items I acquire before using them. 

I really hadn't given the whole prewash idea too much thought in the past when my projects were mainly for myself or my family. This was most likely due to the fabrics I chose to use in the projects. But, now that I am working with a lot of different materials, I have seen first hand why it is better to prewash. 

For example, take a look at these two kitchen towels. 

The one on the left is washed where the one on the right is just out of the package. There's a pretty big difference in size!  And this is after I ironed them both as best as I could so they would lay as flat as possible. 

By the way, these are 100% cotton and from the same package.

Here's a closer look at the weave. As you can see the towel on the left has a much tighter weave than the one on the right.  This clearly shows how much the towel has shrunken during washing. 

This last photo shows just how much shorter the shrunken (aka washed) towel is - a good 2 inches. (You can't see it, but I matched up the bottom edge of both towels.)

Now, imagine you spent your time and money making a shirt. When you were finished, it fit nice and you were very happy with it. 

Then, you wash it....guess what?  There's a very good chance you are not going to like the shirt you worked so hard on. 

The shrinkage impacts the final work in other ways too. For instance, what if this fabric was used with another fabric that didn't shrink? The finished project would have puckering where the two different fabrics were sewn together. And it could be ALOT.  That could wreck a project entirely! 

I have also found this with the machine embroidery I have been doing lately. Unfortunately, I used some of these towels for tote bags - with embroidery on the front. I'll be washing them up later to see what they look like. They may not be any good. I'm hoping for the best. I have 6 of these towels with embroidered pictures and two have already been made into tote bags with other cotton material for the sides and bottom.  I'm slightly anxious to see how they are after washing. Let's hope for the best. 

Another reason I have seen mentioned for prewashing is because most commercially purchased fabric has some type of "sizing" added to it. This is generally on the lines of a light starch and is done so the fabric is crisp with neat folds. It looks nicer on the store shelf or in pictures online. Prewashing removes most if not all of this leaving the fabric quite a bit softer. 

Also, darker and vibrant colors could bleed or run when washed. I once had a pair of dark purple pants that ran in the wash - cold water - every time I washed them. The first time I was not aware they would run and everything in that load had a light purple tone to it!  Another time, a red shirt ran and caused the whole family to have PINK underwear and socks! I even recently found that I have a navy blue pair of pants that run - even though I have washed them many times. 

So, I would strongly suggest you prewash your material before spending the time using it in a sewing project. 

CAUTION: not all material should be washed and dried as you would with the clothes you wear. Some need special handling - like dry cleaning. If you are in doubt about the handling of the material you are using, do a little search online to find the correct way to prewash - it may not even need prewashing. 

Resources 

I found these links that will give you more information. 

Should I wash fabric before sewing?

What can and can't be washed at home?

How to prewash fabrics.