Have you ever blocked your fabric before? Honestly, I didn’t before I went to school. I assumed it was only reserved for extreme cases of off grain fabrics. Like where it’s very apparent and you can see the weaves going on a slant.

So when we were preparing our muslin for draping in class (currently enrolled in draping classes for pattern making) our instructor explained how to block our fabric and why it’s so important. This was so eye-opening! I now can see why it’s so important to pay a little more attention to your fabric before you sew. I am only going to talk about woven fabrics in this blog post since knits is something I do need to study more about and soon will learn about later on in the semester.

Lets back up and talk about what is “blocking” your fabric?

Blocking fabric is when you are manipulating the yarns of the fabric so the crosswise grain and the lengthwise grain run into each other at a perfect right angle.

Why would you need to do this?

Having the grains off on a fabric will have an impact on your garment. Each grain on the fabric has a different behavior. So lets say if you cut a pattern piece out on the lengthwise grain but didn’t know it had a slight bias cut in it (because the grain was off to start with) your fabric will stretch over time. You can expect some waviness.

(Here is an example of a piece of muslin where you can see the grain is off. The selvage is straight on the wooden ruler and the bottom edge is not completely touching the bottom plastic ruler to form a 90 degree angle at the bottom right corner)

Here is a link to learn more about how a woven fabric is weaved to have a better understanding.

Why are grain lines so important and what does it mean? 

Like I mentioned before each grain line will behave differently.

*Lengthwise grain (warp) is the strongest, most stable, this runs parallel to the selvage.

*Crosswise grain (weft) perpendicular to the selvage is weaker than the lengthwise grain. Usually will have a slight stretch compared to the lengthwise grain.

*Bias and True Bias grains is the diagonal line across the weave (true bias is exactly on a 45 degree angle) and will have some stretch as the grains can possible give you. If garments is cut on the bias it will drape more than the other grains.

grains copy

*** This is why listening to the patterns grain lines are so important. The pattern maker is telling you which grain line the pattern is suited for. You should also pay attention to grain lines on interfacing pattern pieces as well. ***

How can you tell if the grain lines are off?

  1. The quickest way but not always the most reliable is when you fold the fabric lengthwise (selvage meeting selvage) and cut lines are met. There will be wrinkles on the folded side. When you try folding it again to remove the wrinkles, then the cut edges and selvages will not meet up exactly.


2. Remove a crosswise thread. This will allow you to see better if the crosswise grain is perpendicular to the lengthwise grain. If it’s not then your grain is off

3. In school we were taught to clip the muslin fabric into the selvage and rip it all the way across the cross grain. The rip will follow the weft yarn and show the true crosswise grain. When you take a look at your fabric you see if the crosswise grain meets the lengthwise grain at a right angle on all four corners.


Example pictured here on the piece of muslin.

How do you correct this problem?

It seems like there might be more than one way to do this, but I’m going to only talk about what I have learned to do. Take the corners of which you want to adjust. Tug on it along the bias. Give some good tugs all up and down the bias until the corners are now at a right angle. Crosswise grain should now be perpendicular to selvage. To double-check, take a L-Square ruler and place it on all corners to see if all corners are at a right angle.


(Red line represents the bias) This is the same fabric piece shown above .

Now you can see the fabric’s crosswise grain is now perpendicular to the selvage.

(Revised and added after publishing this post. The following information given to me by a professional in the fashion industry)

Why would grains be off on woven fabrics in the first place?

This was explained to me by Shilo Byrd her Instagram here. The reason why grains would be off or collapse is not because they are badly woven or because it’s bad quality. They collapse because of how the fabric is stored. Time and gravity will make this grain line fall and distort. When a fabric is woven it is woven horizontally to the floor and rolled on tubes. Those tubes are then stored horizontally on shelves. So sometimes when fabric is shipped or sold to another seller they have a tendency to store the bolts vertically. Which then makes the crosswise grain collapse.

Hope you learned a little something along my journey. Follow me on Instagram here where I share some more behind the scenes.




  1. Many thanks for this great blog post. I have to admit that I sew since about 10 years and never blocked fabric before. Today I was about to start a shirt dress out of a checked /plaid(?) fabric and realized that the fabric is off grain. I will now try this tutorial. Wish me luck 🙂
    Greetings from Germany,


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