The following are just my observations, your mileage may vary.
When I first expressed an interest in trying to sew with period tools (specifically brass pins, and needles made of bone, brass, or hawthorn) most of the reactions I got were negative. Not negative in the “oh dear gods woman don’t do it” but skeptical as to how effective the tools would be vs modern steel needles and pins.
The general consensus is that, while such tools are period, they aren’t worth the hassle and frankly they’re too brittle or soft or thick to be very effective anyway. The holes they’d rip in the fabric would look huge compared to modern needles, and they’d keep breaking in the middle of a project, and they’re only good for loosely woven fabrics. To that I say: you’re probably thinking of and using them wrong. Don’t think of them like modern needles, think of them more like tiny awls.
When you use a modern needle it’s sharp enough that it’ll cut threads in it’s way when you push it though the fabric, and it’s strong enough that you can make several stitches at the same time when doing a basic running stitch. This makes hand sewing quick, but also puts a lot of stress on your needle, your thread, and frankly limits how tiny your stitches can be based on how thick your fabric is.
Trying to sew the same way with bone needles will cause them to break. Ask me how I know. Aethelflied: making mistakes so you don’t have to!
For bone and hawthorn (I’ll get to brass in a minute) the best method I’ve found is the single stab. Push your needle through the fabric once, pull your thread through, push your needle back up through the fabric, repeat until your seam is done. This is a little slower until you get used to doing it, but honestly I’m much happier with how my seams look.
Why does this method work when multi-stitch running stitch doesn’t? Well for starters because of how bone and hawthorn needles interact with the fabric. Unlike a modern needle which will cut threads in it’s path, these types of needles push the threads aside to pass through. This creates a large initial hole (compared to a modern needle), that closes up around your sewing thread with time and washing. It heals for lack of a better word. This puts less long term stress on your fabric and (in my experience) makes your seams less likely to rip out since you’re not damaging the weave. It also gives us a reason why the needle holes we see on extant garments are so tiny compared to the needles we know they had at hand.
Sewing this way also puts less stress on your needle itself since it’s only going in one direction and does not have ripples of fabric trying to bend or snap it. It also puts less stress on your sewing thread since it’s only passing through the fabric once in a single pull. This makes this method wonderfully suited for handspun thread since you can afford to be a bit more finicky/careful pulling your thread through your fabric you’re less likely to snag and snap your thread.
This also allows us to create the tiny stitches we see in period that (I was told) could not be accomplished with bone and hawthorn needles because they were too thick/brittle. Because you’re not limited by how much of your needle is already caught up in the thickness of the fabric when you go to create another stitch you’re free to space your stitches as close together as you’d like. I’ve seen documention (in an article on irish bog finds, specifically mentioning hats, that I did not bookmark but have been trying to track down for the last two years) of stitches being as close together as 3mm. Stab-stitch method makes that possible with period needles.
What about brass needles? Well to be perfectly honest I only have one and it’s my least favorite to work with of the period needles I own. Brass is soft, so I can only use it when it’s either cold or I’m in air conditioning. Even then I need to take frequent breaks so the heat of my hands doesn’t bend the needle more than it already is. That being said brass is so much better for delicate fabrics like very light weight silk because it is so much finer than bone or hawthorn. It doesn’t *quite* function like a modern steel needle, and using it like one will bend and distort it (ask me how I know), so you still want to use the stab-stitch method, but it’s almost as fine as a modern needle so it is less likely to create pulls and snags in your delicate fabrics.
A note on working with brass in general: I use brass sewing pins when I’m hand sewing at events because modern pins are glaringly anachronistic to me if I’m the one using them, not a snobbery thing, not going to judge anyone else for their modern pins, but I judge me. BUT! Keep your fabric dry as best you can if you’re working with brass. It will patina. That means lots of little green dots which, depending on your fabric, may be difficult to remove. Pin a small section at a time, especially if it’s humid, and don’t leave your pins in your garment if you’re not actively working on it and it can be avoided.
Why bother with this at all when modern hand sewing tools work faster, are easier to acquire, and no one can tell what you used when you’re wearing the finished garment? For me the joy of making garb is accuracy. I feel like I’m a horrible cheater head when I use a sewing machine, and frankly I’m starting to feel that way about steel pins and needles. Again, this is just for my garb. I’ll sewing my husband garb on a machine, serge the seams, and be perfectly happy with it. I see garb people have machine stitched and am in awe that they made their own clothes and proud of them for either sewing it or making period style garb with their very own money. But for me? For me I want to make it as correct as I can. Right down to the bits no one knows but me.