Do I really need to prewash my fabric?

September 14, 2023 4 Comments

The short and sweet answer is YES!

Hi, Mary from the Sew Mary Mac Blog here to give you the long answer to this question! We’ve all been there~you get some brand new RCF fabric and you just want to cut into it and get it sewn up ASAP.  But there are several reasons why you should always prewash your fabric before sewing them up.  Keep reading for the long answer!

Have you ever noticed that some of your natural fiber RCF fabrics feel a bit stiff when you receive them?  Some might even find they feel a bit sticky or tacky.  This is because RCF uses an environmentally friendly printing process.  The inks used are OEKO-TEX certified and biodegradable.  Th in house printed fabrics are NOT washed or steamed after printing.  This saves 20 gallons of water per yard of natural fiber printed fabric!

When prewashing your fabrics, they will soften right up.  This makes them much easier to work with. Bonus:  RCF cotton jersey and French terry is known to get softer and softer with each wash!

It is not uncommon for fabrics made with natural fibers to shrink.  If you don’t wash your fabrics prior to sewing you might wind up with a garment that doesn’t fit or doesn’t fit correctly.  

Just how much do certain fabrics shrink?  I did a little experiment to show you exactly how much different fabric bases can shrink.  In order to do this experiment the RCF shop sent me a pile of ½ yard pieces of various fabric bases.  

Most fabrics reacted as I suspected they would.  The only unexpected result was the Bamboo/Cotton jersey.  I was expecting some shrinkage there.  Note:  I did not have a piece of the infamous Oatmeal French Terry in my stash that wasn’t already prewashed.  I find this French terry shrinks a tad more than the others.

Many times it is recommended to prewash fabrics as you’re going to treat the finished garment.  While this is perfectly acceptable and logical, I always worry “what if?”.  What if my finished garment gets washed in warm instead of cold by accident?  What if my rayon blouse gets thrown into the dryer by mistake?

One of my favorite fabrics at RCF is the rayon challis.  I find it less “shifty” than others and so easy to work with.  It’s also a great fabric to wear in warm weather and great layered in cooler weather.   

Some people hand wash their rayon challis and hang it to dry. Personally, I always wash my finished rayon challis me-mades on cold and hang them to dry.  But I ALWAYS prewash the fabric on warm and dry in the dryer before I cut and sew them up.

Prewashing eliminates any dust or dirt from your fabric.  It will also remove chemicals and sizing from the production process.  

As you can see from the chart above, synthetic fabrics don’t shrink, but it’s always a good idea to work with clean fabrics.

Tips for Prewashing

1. Finish the edge of woven fabrics*
2. Unfold fabric
3. Don’t overfill your washer
4. Wash similar colors together 
5. Wash solid cotton jersey and french terry separately as some colors may bleed.

*Wovens can be finished by serging, sewing a zigzag stitch on the edge or by cutting the edges with pinking shears.    If not finished you will lose even more yardage because of fraying and wind up with a tangled mess. Bonus~  when you finish your edges before prewashing you can always tell which fabrics in your stash have been prewashed!

Conclusion

Always prewash your fabrics!

This custom printed Rayon Challis is from Cheryl Graham Designs and can be found HERE.  My favorite pattern to sew up with RCF rayon challis is the Rhapsody Blouse from Love Notions.  You can find that pattern HERE.  

Visit this Sew Mary Mac Blog post to read all about my Love Notions Rhapsody Blouse collection and see tons of RCF rayon challis sewn up!

Thanks for reading and happy sewing!! 

Mary Anne :)

If you’d like to read more about my sewing adventures I would love for you to visit my blog, Sew Mary Mac.  You  can also follow me  on Instagram  @sewmarymac to see all of my makes. If Facebook is your thing, you can check out the Sew Mary Mac page.

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