When it comes to designing sewing patterns for stretch fabric, using negative ease is absolutely essential to creating the perfect fit. This is because knits stretch and knit garments are designed to stretch to fit the body, and without negative ease, the garment would be loose and awkward. We define the stretch ratio of a knit fabric as the degree to which a fabric will stretch from its original length. Calculating the stretch ratio of a knit fabric is important to ensure that the correct amount of negative ease is applied to your sloper and subsequent patterns. It is important to note that not all knit fabrics have the same stretch ratio, so every time you change your fabric you must re-calculate the stretch ratio and re-draft your slopers to correspond with the amount of negative ease required by your fabric. Stretch and recovery are also important factors to consider when working with knit fabrics. Good stretch and recovery means that the fabric will return back to its original shape after being stretched, which is necessary to ensure your final garment fits correctly. When drafting for stretch, using the correct amount of negative ease allows for the creation of garments that beautifully contour to fit the body.
What is negative ease and why is it important for designers to understand?
Negative ease is the amount of space that is subtracted from a garment to allow for the fact that it will stretch when worn. Recall the definition of stretch ratio being the degree to which a fabric will stretch from its original length. Later on in this article, we will discuss more in-depth on how to determine the stretch ratio of a fabric and how to calculate the percentage of negative ease using the stretch ratio. In brief, once the stretch ratio has been determined, the stretch ratio is then used to calculate the percentage of negative ease. Once the percentage of negative ease has been determined, the negative ease percentage is then used to calculate the total amount of negative ease to be subtracted from a body measurement to draft a pattern that is smaller than the body. This is the complete inverse of working with wovens, where positive ease is added to the body measurements.
For example, if a leotard is drafted for a bust measurement of 36” and is made from a fabric with a negative ease percentage of 25%, then the negative ease to be subtracted from the bust measurement of 36" would be 9” calculated as such, (36”- (25% x 36”)), using the formula (body measurement - (negative ease percentage X body measurement). This means that when the leotard is being worn, the bust circumference will stretch up to 9” to fit the body (27" of fabric will stretch to 36").
Negative ease is important for designers to understand because it allows them to create stretch garments that will fit the body correctly. Without negative ease, garments would be loose and baggy, and would not contour to the body in the way that they're supposed to. When drafting with negative ease, as opposed to positive ease, the garment is made smaller than the body and will stretch to fit the shape of the wearer. Generally, we only apply negative ease to the measurements that encircle the body to provide flexibility when the body moves. It is also important to calculate the stretch ratio of a fabric before adding negative ease, as not all fabrics have the same degree of stretch. This is something that must be taken into account every time you change fabric, as it will affect the amount of negative ease required and affect the final fit of your garment.
Negative ease is an essential part of stretch garment construction, and one that all designers should take the time to understand. By taking into account the stretch properties of a fabric and calculating the correct amount of negative ease, you can create garments that fit beautifully and flatter the figure.