Hold the fabric up to the light and see what happens
Short answer: If you can see your fingers clearly through the fabric, it is thin or loosely knit. That says something about both coverage and durability before the item has even been worn once.
What you can actually see
Hold the fabric up against a window or a lamp, with some distance between the fabric and the light source. A tightly knit fabric lets through only a little light and looks even across the whole surface. A loosely knit fabric shows clear gaps between the stitches and lets through far more light.
What it means for wear
A lot of light coming through means transparency in ordinary daylight and usually less durability over time too. For a white t-shirt or a light blouse, this is the most important test you can do before you even pay for the item at the till. See bamboo t-shirt for women as an example.
Unevenness becomes visible too
Against the light you can clearly see whether the yarn is evenly spun or has thicker and thinner sections spread across the fabric. Even yarn gives a neater and usually more durable fabric, while unevenness often points to faster production rather than careful craftsmanship behind it.
Try the test yourself
See bamboo clothing for women and bamboo t-shirts for men and try the test on an item you already own and are happy with, so you have a reference to hold new pieces up against. That makes it far easier to judge a new item next time you are standing in a shop or looking at it at home by the window.
Test several spots on the same item
Do not hold up only one part of the fabric to the light. Check the front, the back and a spot near a seam, since quality sometimes varies slightly within the same item, especially if it was sewn from several smaller pieces of fabric from the same roll.
What color does to the test
A light or white color makes the result of the light test far clearer to see than a dark color does. On black or navy fabric, even a loosely knit fabric can look tight in ordinary daylight, so judge dark clothing a little differently from light clothing.
Combine it with the stretch test
Combine the light test with a light stretch of the fabric while you already have it in your hands. A fabric that both lets a lot of light through and stretches a lot easily is typically the thinnest and least durable you can find in that type of product.
Use it as a quick first sort
Use the light test as a quick first sort when going through several items in a short time. It takes only a few seconds per piece and can save you time on items that would end up put back anyway after a closer look at home.
Test it again after washing
Try the test again on an item you have already washed several times, to see whether the fabric has grown thinner over time. Some fabrics stretch slightly with washing and become more see-through, which can be useful to know before buying more of the same kind.
Frequently asked questions
Is thin fabric always bad
No, not at all. For summer clothing and underwear, thin fabric is often an advantage rather than a downside. It mostly comes down to what the item is meant for, not thickness alone.
What about dark colors
Dark fabric is less transparent regardless of how tightly it is knit. The test therefore says the most about light colors, where the difference between tight and loose knit becomes far clearer in practice.
Can this be tested in an ordinary shop
Yes, hold the item up against a window or a ceiling lamp. Most shops have enough light for the difference between tight and loose knit to become clear enough.
You can find the full range at Bamboo-Clothing.com.
