That is the question.
Whether you bring home a few fat quarters or a big bag of new fabrics, you have a decision to make before you take that fabric to your sewing room.
You have just two choices:
1. Leave it in the laundry room until you have time to pre-wash and dry it all. (Then to the ironing board to press, fold and store in whatever system you have developed that enables some possibility of finding it again.)
2. Skip all but the last step. Bring it straight to your sewing area, put it away and use it as needed.
We can all see why #2 is the choice for many quilters. But. I am not one of them. I pre-wash everything.
Technically, I should say pre-soak since I don't use soap. I use cold water and a big pure white plastic bowl from the $1 store. (A white dish washing tub will work, too.)
This allows me to see any dye creeping out into the water. Sometimes it is immediate. If so I drain and refill with cold water.
(Investigate the product Retayne if something keeps bleeding and re-think using the piece in your project)
Even if nothing shows up at first, leave it there for maybe 20 minutes. Most fabrics hold excess dye. It can come out now, or after the first time water hits it. After spending months or years making a quilt for yourself or for a gift that is a risk you take.
The photos you see are of high quality batik scraps given to me by friends contributing to a quilt I'm making. All told me the fabric was not pre-washed so I grouped the scraps by color and these photos are typical of the results.
There are varying opinions on this issue. Some say blues and reds may bleed (see the gold/yellow above). Others say today's fabrics really don't "bleed much". Not true.
If you make bed quilts and want them to be used as such, they will be washed at some point. To me, it makes sense to minimize the possibility of ruining a quilt the first time it's washed.
Wall hangings may be an exception as they are rarely washed but it makes sense to be consistent. If you have not previously pre-washed and believe you should start, you can usually tell pre-washed pieces by the somewhat frayed edges. When in doubt, just soak the questionable fabric before using to be sure. Then from now on, pre-wash any new fabrics you acquire.
Besides the risk of dye bleeding, other benefits of pre-washing include shrinking the fabric and removing sizing chemicals.
There is no guarantee that pre-washing will prevent all bleeding. The first time or two I wash a quilt I am cautious. I used cool water and mild detergent. I toss in several dye catcher sheets and examine the quilt when it comes out of the washer. I use medium heat in the dryer and watch it carefully. I find the quicker it dries the less chance of darker colors seeping into the light areas.
For me, part of the pleasure of textiles is handling and admiring them so I relax and enjoy the process and I sleep well knowing that I've done what I can to minimize 'bleeding' later.
To read a past post about my quilt washing experience with details about my process click here.