𝗪𝗵𝗮𝘁 𝗶𝘀 𝗡𝗘𝗚𝗔𝗧𝗜𝗩𝗘 𝗘𝗔𝗦𝗘? 𝘞𝘩𝘺 𝘸𝘦 𝘶𝘴𝘦 𝘪𝘵 𝘰𝘯 𝘴𝘸𝘪𝘮𝘸𝘦𝘢𝘳.
Ease is the difference between your real measurements and the pattern piece, or fabric piece when cut. The difference between your measurement and the finished garment.
I first heard about this concept with Stuart Andersson, and it was a fundamental moment for me to learn more about this concept.
You can find lots of sources online, explaining the concept and I really liked the video from Anika from Made to Sew where she explored the concept for non stretch fabrics.
The mail goal for using ease is to make the garment fit you comfortably for any fabric type.
Let's say you have these measurements:
Now, imagine you want to make a dress pattern with a pencil skirt style bottom and are doing so with 100% cotton fabrics. Do you believe you could do this by just adding seam allowances to your measurements and design it? Of course not. You would have to increase the measurement around your body (horizontally), making it so hat the dress would fit you. This would be adding positive ease to your measurements so that the non stretch cotton would comfortably fit you.
The percentage of how much you increase the measurements depends:
1 - On de fitting desired (more or less form fitting)
2 - On the fabric (stretch or not and with stretch percentage)
3 - On you personal taste (so you can feel comfortable)
Let's work with an example:
If my bust is 102cm and I'm designing a non stretch top, I will increase the ease (positive ease) with 5% witch means 102cm plus 5%= 107,10cm (example).
If I were to do the same, but applying negative ease, I would calculate: 102 minus 12% Negative ease = 89.76cm. This would be the case with stretch fabrics.
When we, at Bikini Design Club design swimwear patterns we calculate according to each design and pattern the correspondent negative ease. When designing swimwear, and since the fabric stretches, we always apply negative ease.
We do so by reducing a certain percentage when we design the patterns, so when they are finished, they stretch and fit you nicely. This is different for reversibles and non reversibles and that's why we always recommend you follow the pattern instructions.
With this concept explained it turns quite obvious why a reversible swimsuit is very different from a non reversible and why the design for each type should be different regarding ease. 2 Layers of swimwear fabric stretch less than one layer of swimwear fabric and one layer of lining.
Off course you can still do sew tops and bottoms with your Prefered method and not respecting the design feature and designer intentions regarding being reversible or not, but if you do this for a Swimsuit, you'll be able to confirm that it's really not the same and the design needs adjustments.
A non reversible swimsuit made with 2 main fabrics will fit you smaller then intended and will probably roll over...
If you're wondering about the vertical ease, well, vertical ease is generally zero% since the greater shape differences are on horizontal measurements like bust and hips. Of course you can adjust a pattern to fit a specific Torso if your measurements are very different than the average.
For us at Bikini Design Club, designing Swimwear patterns has been a long journey. Despite we started recently and with no design or fashion background, it was always obvious that we wanted to learn has much as possible to be able to provide the best patterns we could and so we've dedicated many hours searching for knowledge that would able us to provide nice fitting patterns on our store.
Hope this post was an easy and simple way to inform about what's Negative ease so from now on you can make informed choices on the patterns you sew.