I've recently been asked about the types of thread that I use for tablet weaving. To be honest, like anything, much depends upon just how 'authentic' the finished weave is meant to be, and how much money is to be spent on the materials.
If I am teaching, I tend to use a #5 perl cotton. It has a little bit of a sheen, and in many ways resembles a spun silk. It is a medium weight, so the weaving moves along at a nice pace, and you don't need too many tablets for a nice width. Because of that, it can also be unwoven fairly easily if a mistake is made, and is generally a good all-rounder. And it's great for belts, that sort of thing.
Finer cottons are lovely too. Not 'authentic' * Choose something with a good twist and the pattern will be crisp and when you weave. Crochet cottons are really quite lovely, and really do lend themselves to some fine weaving at reasonable prices.
Wools. Well, the general consensus is to stay away from wool threads until you are experienced. Which is a good tip - particularly if you are trying to achieve a fantastic Viking or Anglo-Saxon weave. They don't look any good in a fat knitting wool, but a fine worsted wool will snag, fluff up and probably snap at least once while you weave. I often see quite thick wooly braid for sale, made with rather thick knitting wools. Yes, it can be pretty quick to weave these, which of course means the price can be really reasonable when you want to trim a tunic, but, they are often just that bit too thick and can unbalance the way the tunic hangs. So, you do need to consider this. There is no point buying a lovely fine woolen fabric only to sew a thick braid to the hem. Of course, a thick braid in a modern context can be quite spectacular.
Silk. There are two types of silk out there, and many people confuse them. There is spun silk, and filament silk. And if you are going for 'authentic', you really have to choose filament.
Spun silk is what is generally more easily available today. It is made from the broken or damaged cocoons - these short fibres are spun together in the same was as wool is spun. Because the short fibres are used, spun silk often has a fluffier appearance than filament, and always has less sheen. Histrically, spun silk does seem to have existed - English medieval silkwomen complained at the poor quality silk they were getting from the Italian merchants - but it does not seem to have been happily used by them. Most of what survives has been made using filament silk, with the odd exception - weft threads sometimes appear to be spun, as do the odd tassel, fringe or braid.
However, with modern machinery, there are some nice spun silks out there, and I know lots of tablet weavers who use 60/2 spun silk for most of their work. Something with a tight twist will give a crisper design. And of course - it is great for modern applications as well.
Filament silk is the continuous length of thread as it is unwound from the cocoon. As such it is strong, very shiny, and quite unlike spun silk. It can be loosely twisted (a floss) or tightly twisted. Weaving with (and generally working with) a filament silk is, for me, a real joy, even though the fineness of filament silk can mean a really time-consuming project. I use both floss and tightly spun silks in tablet weaving, tightly spun threads give a denser, sharper appearance, whereas the floss silks, used in multiple plys, can give a very fluid, fabric-like weave.
And you know, sometimes experiementing with modern / unusual threads can be quite fun and give great results. It is easy to get caught up in the whole historic thing and forget to be a little creative sometimes.
*(a word that I sometimes really dislike. More on that another time.)
Hopefully that's a help to some of you! As for me, still brocading. The second piece is much more time-consuming than the first was! But pretty. The website re-build is moving along very well, and I have some very exciting things in the pipeline, it's about all I can do to not blab!