Here is a very basic guide to considering the denim fabric on a chosen pair of jeans. For now, let’s concentrate on the denim itself and ignore the dye/coating, etc. Please do let me know if I’ve missed something important!
Firstly let’s consider how the cotton yarn is spun prior to the weave. Traditionally, a ring is used to spin the cotton – the cotton fibre used were of a longer variety than is commonly used now. There are thin and thick portions along any given fibre, and as a result of this, the fabric that is woven has an uneven surface. Jeans made back in the good old days used both ring spun warp and ring spun weft, so called Ring/Ring denim.
Most yarns nowadays, however, use open-end spinning, a process introduced in the 1970s. This new process omitted several steps in the traditional methods, whilst boosting production capacity, lowering production cost & lowering the frequency of faults occurring in the fabric. The denim that is produced with open-end warp and weft, however, are not what we desire in our hobby. The denim is bulkier for any given weight of denim (due to the fact that the denim is less dense), is coarser (less comfortable), takes in more dye (due to a larger surface area of cotton exposed), and ultimately is much weaker & doesn’t age very well.
Some manufacturers nowadays also attempt to recreate the look and feel of Ring/Ring denim by combining ring spun warp with open-end weft. The resulting fabric, however, is still weaker and coarser than Ring/Ring denim – RingRing is truly the real McCoy.
Different makers, of course, have their secret ways of altering the denim, from Samurai’s addition of short fibres into the yarn to SugarCane’s drastic change of half the yarn material to sugar cane fibre. This keeps the hobby interesting – there is an endless variation in the texture & ageing of denim, and as such every new pair is an unknown adventure 🙂
Secondly, consider whether the denim is sanforised or unsanforised. Sanforisation is a process (invented in the 1920s) which stretches, shrinks & stabilises the denim before it is cut – as a result, the denim will not shrink significantly when soaked or washed. Due to this process, sanforised denim tends to have a slight sheen/glow to them. Most, however, prefer unsanforised denim, since the ‘shrink-to-fit’ method is infinitely more fascinating, and most find that the hue/fading on unsanforised denim is more desirable. Sanforised denim usually shrinks up to 3% along the grain after soaking, whereas unsanforised denim can shrink up to 10%.
Thirdly, consider the twill-handedness. Right-hand-twill means that the grain runs from the bottom left to the top right, in left-hand-twill the line runs from the bottom right to the top left.
RHT is the traditional way of denim weaving and much more common than LHT. The LHT, by virtue of it’s construct, offers a softer hand – therefore, the fading on a pair of LHT jeans will generally be more blurry/vertical than a pair of RHT jeans. The legs of the jeans will also twist in different direction, RHT to the right & LHT to the left.
Lastly, let us consider the mass of the denim. This is traditionally defined as the mass, measured in oz, per yard of denim – that is, a yard of denim 29 inches in width. This can range from a 4 oz skirt to a pair of 24 oz Samurai Jeans. In many instances, manufacturers would use a 1 warp to 2 weft combination (or a variation of such) to boost the mass. When choosing the denim mass, please consider comfort & utility – it would be a silly idea to wear a pair of 21 oz in Malaysia, and you wouldn’t want to be in Hokkaido during winter with a pair of 12 oz.
Denim mass is a little more complicated than just the stated mass of the denim, and heavier doesn’t mean it’s any better or stronger. The strength of a garment is much more than the weight of its fabric – but this won’t be discussed here, but suffice to say, if you want the strongest pair of jeans, you’re in the wrong hobby (you’d be better off with a pair of poly/kevlar jeans). Heavy-weight vintage denim with cotton stitching cannot be considered protective clothing, no matter how heavy the denim is (it’s still cotton) – I don’t care how much anecdotal evidence you’ve heard about some guy falling off his bike and his Iron Heart jeans were unharmed. Abrasion is the least of your worries in that situation anyway…
I personally favour denim that is between 13.5 and 16 oz for everyday wear. Notice that the stated mass refers to the denim at it’s most dense (meaning, post-wash/soak) – so, another reason for soaking before wearing 😛