Poplin is a plain-weave cotton with a very fine rib in it, created by packing more threads across the cloth than along it. What that gives you is a smooth, faintly lustrous surface, a firm handle, and a crispness under the iron that outlasts almost every other shirting through a full day. There is a reason it became the default cloth of the business shirt. A shirt in a Thomas Mason or Alumo 100/2 two-ply poplin is about the clearest statement of what a dress shirt is meant to be: smooth, precise, cut to fit, and still looking respectable twelve hours after you put it on.
What the weave is doing
Poplin is a plain weave, so each weft thread goes over one warp thread and under the next, all the way across. What sets it apart from other shirtings is the thread count and the ratio between the two directions. The weft thread is finer than the warp, which produces an extremely fine rib. You will not see it with the naked eye, but you will feel it. That faintly structured smoothness is how you know you are holding good poplin.
Two-ply poplin, woven from two threads twisted together rather than one, is the standard for a decent business shirt. The twist adds strength, cuts down pilling, and gives a smoother and more lustrous surface than single-ply. The Thomas Mason 100/2 two-ply we use has 100 threads per centimetre in a two-ply construction, which makes a cloth that is very fine and very smooth while still being firm enough to take a press and hold it.
Why poplin suits this city
Over 30 degrees for most of the year, humidity that does not let up, and a working day that involves at least one walk across a hot car park. Poplin handles all of it. The tight plain weave lets air through without the cloth feeling flimsy, it takes a press and keeps it, and it does not go limp and shapeless in humidity the way a looser weave will by lunchtime.
The weight to look for here is 80 to 90 gsm. Fine enough to actually feel cool on your back, heavy enough to have some body and hang right. Lighter poplins at 60 to 70 gsm are cooler still, but they can look slightly see-through in strong daylight and they crease more, so think about where you will be wearing it. Heavier poplins at 100 to 120 gsm are better suited to men who spend the whole day in air conditioning and are never really hot.
Colours and patterns in poplin
Because the surface is smooth, poplin shows colour honestly and pattern cleanly. A white poplin is truly white, since the flat surface throws light back at you. A pale blue is an even blue rather than the slightly patchy tone you get from looser weaves. Stripes are at their sharpest in poplin, with the pattern coming through undisturbed by any texture in the cloth.
For a first poplin shirt, take white or pale blue with a spread collar and barrel cuffs. That shirt works in every professional situation, with every suit and every tie you own. After that, the sensible additions are mid-blue, white with a fine blue stripe, pink and pale grey. Bolder colours, deeper blues, greens and burgundies, come out beautifully rich and clean in poplin, and they are worth ordering once the plain ones are in the cupboard. Just do not start there.