To Pre-Wash Or Not? A shame-free approach to fabric prep.

It's a very controversial stance, but I barely pre-wash my fabric. Test, yes, but wash out the starches that make sewing so much easier, disrupt those grains, nah.  

It is a drag to press a large fabric post-wash perfectly; I know it's not happening, which will impact the cutting. So if you're pre-washing, you want to know it's worth it. 

OK, here are a few caveats: 

• I work with high-quality fabrics - not exclusively, but mainly. Not shrinking and quality isn't alway linked but there is more probability of fabrics being tested for shrinkage. 

• Wool is a different scenario. Test wool as you approach cleaning it. I pre-soak my looser woven coating wools (no agitation and a flat dry, similar to blocking for knitters) as I clean my finished coats the same way. It's not conventional and comes with risks, but dry cleaning is so toxic I choose not to do it. 

• I'll test Merino knits and adjust a pattern to match shrinkage well before pre-washing because cutting it post-wash is a total pain.

• I would always wash raw denim and add vinegar to set the dye. Denim traditionalists may have differing practices here.

• Cellulose-based fabrics often become crunchy when wet and dry shrunk but can be pressed back to size.

• Dye lots can change fabric; test each colour if you buy the same fabric in a few colours. 

The test may feel like another layer of prep, but it will save you time and fuss overall. 

1. On a spare part of your fabric, mark a 20 cm x 20 cm • 7 7/8" x 7 7/8" square. Don't go smaller than 10 cm. You won't get the results.

2. Add an arrow to indicate the grainline this is to see if shrinkage has only occurred along the grain or cross grain.

3. Cut around the square, leaving borders, Measuring edges post-wash can be tricky. It's better to measure the square inside the sample for accuracy. 

4. Check the accuracy of your drawn/sewn square at a few points to ensure consistency.

5.Pour boiled water(or very warm for the synthetics ) on it and allow it to cool.

6.Dry, press, and remeasure the fabric.

You might be surprised at how few fabrics shrink permanently.

If you have any shrinkage, calculate what it is as a percentage. You can then use this percentage to judge if it's workable shrinkage or needs a wash first. Example below.

• 1% of the pre-washed sample = 20 cm  / 100 = 0.2 cm

• Post-wash measurement = 19.6 x 19.6 cm 

• Post wash, 19.6 cm / 0.2 cm = %98 

• Pre 100% - Post 98% = 2% shrinkage 

• Size 10, Bust 91 cm - 2% = 89.18 cm 

• Size 30, Bust 141 cm - 2% = 138.18 cm

Now armed with the percentage of shrinkage, you can figure out if it would be impactful. If you're in between sizes or the style has a lot of ease, it might not be worth washing out all the starches.

2% shrinkage on the grainline will only affect the length. This could be a 1 cm difference over a sleeve - For tall people, this matters, or for the short, this could be good.