How to choose the perfect rope
I get asked a ton about my recommendations for rope and rope types and lengths of rope, so I'm going to put it all down here so that it's easy to refer to later. This is how I choose rope for myself. It includes my preferences and choices. My "right" rope may not be your "right" rope but these are the things that I look for when buying for myself or recommending to someone else.
I am a jute whore. I love tying with jute because it's fast and light and when made correctly is a lovely pale gold color. Jute is scratchy and weaker than all of the other rope types we use for suspension but the handling and speed that comes from using it trump those disadvantages, in my mind (1). All of the rest of this article is to do with jute, not any of the other types of rope (2).
I will only buy machine made rope these days. There are two main reasons for this. The first is that it's more consistent. When rope is hand made, it's usually made with a drill and has a lot of allowance for human error, resulting in a less consistent wind or lay. This inconsistency has significant implications for the life of the rope and its overall strength. Secondly, hand made rope is missing one very vital thing in the rope because it's simply impossible to put there without a machine. It is missing a single thread within each of the strands that runs straight down the middle and is not wound but rather all of the other threads are wound around it. This single strand adds tons of strength and lifespan to the rope. I will no longer buy rope that does not include this core thread. Yes, this means that I'm importing my rope and not buying American made products. No, I will not compromise in this case. It's too important.
I like my rope to be about 5.5mm in diameter. I find that 5mm wears down to be too thin to be comfortable for most people and that 6mm feels a bit bulky in my hands. I will not go any wider than 6mm, ever. The knots get too big and start to become problematic in their own ways such as not holding as well and pressing into the body uncomfortably. I have varied between 5mm and 6mm rope for years. I am currently tying with 6mm rope and it's taking some getting used to but because the rope I have meets all of my other criteria, I am willing to be a bit flexible on diameter.
Lay or Wind
I like my rope to be pretty loosely laid, meaning that there aren't as many winds in the rope per inch as some other ropes. This is another area that I'm not willing to compromise on as I consider tightly wound rope to be unsafe. The tighter the wind of the rope, the weaker the rope. This seems counterintuitive because tighter wound rope tends to feel stiff and stable and strong but tension physics shows that a rope is the strongest when it's laid completely straight and the more winds you put in it, the weaker it gets. It's the same physics at play as when we say that each knot you put in a rope decreases it's overall strength. Tightly wound rope also has a tendency to snap more easily when pulled over sharper turns (something you should be trying to avoid but it's occasionally unavoidable).
Unprocessed but still soft
I expect my rope to be usable immediately upon opening the package and I expect it to come to me unprocessed. High quality rope does not need significant processing to become soft and supple. If you need to singe, oil, wax, bake and do other things to make your rope useable, it means that the fibers used were low quality fibers. Jute should be rough but not intolerable and should eventually slick down and get almost glossy with use. If it continues to shed forever, it's not the highest quality jute. I usually will give my rope a coat or two of jojoba oil right when I get it if it feels a bit dry but if it needs more processing than that, it's not good enough.
The highest quality of jute is a pale gold color. If it's white or ivory, it's probably been bleached and severely damaged. If it's a darker brown, it means that the fibers are lower quality and more likely to be scratchy and weaker.
Dyed rope is beautiful but it also means that the rope had to be wet processed and has likely lost a relatively significant amount of strength along the way.
Obviously, this is the easiest to modify post-purchasing but people ask me how long my ropes are all the time so I'm adding it here too. I use 8m ropes. While they are slightly too long for me for the best rope handling (generally the best rope handling comes when the rope is 5 of your own arm lengths) the ropes tend to fit the people I tie quite well meaning that I usually don't have to add a rope just to finish off the last 10 inches of something. This is the one part that I really believe is personal preference but I certainly wouldn't go any more than 10m and I tried 7m once and hated it.
(1) I am not going to argue about the safety of using jute for suspension. If that's what you're about to comment on, move along.
(2) I also despise the synthetic versions of natural fibers, hempex and posh. It's great if they work for you. I hate them for my own use and do not wish to have people try to change my mind.