From the Landsknecht trousers of the 16th to the parasol ruffles of the 19th century, a kind of fabric decoration was employed that would make a modern tailor turn away in horror: Slashing and pinking. Slashing means that slits and/or holes are made smack into the middle of the fabric not just any old how, of course, but in pleasing patterns. This technique was predominantly used during the 16th century and was only rarely used in the 18th century, usually along the edges of ruffles.
Pinking, on the other hand, was quite popular during the 18th century, especially around 1750-70, when robes were decorated with lots of ruffles and ruchings. Pinking means cutting the edge of fabric into little bows or zig-zags. You may be familiar with pinking shears which are normally used to make zig-zag cuts that prevent the fabric from fraying. 18th/19th century pinking was basically the same, only that they didn't have pinking shears. They used iron punching tools with sharp edges instead. Unlike most modern pinking shears, those pinking tools could be rounded and have scallops (rather than zig-zags) within.
Pinking made it unnecessary to neaten the edges of ruffles the normal way, i.e. by turning them twice. Ruffles are meant to be light and flowing, after all, so a turned edge would be too stiff and heavy. Pinking doesn't work for just any fabric, however. Apparently it was, in period, only used on silk. A portrait of Madame Pompadour wearing a printed cotton gown exhibits rolled edges, and in fact pinking cotton isn't easy.
There's a picture in Diderot's Encyclopédie, chapter "L'Art du découpeur", of a woman pinking a length of fabric and of various pinking tools. One of the tools is straight and has pointy zig-zag teeth, so I deduce that modern pinking shears can be used. However, scalloped edges look better and are more typical of the period. The most beautiful edges are made by 2.5-3 cm wide half-circle irons for sleeve ruffles and ruchings, and 6-8 cm wide 1/3 circle irons for larger ruffles, such as the ones on the petticoat.
The follwing hints are based on my experiences with pinking tools:
The most important thing is a hard surface that doesn't resonate. The woman in the Diderot plate is owrking on a thick board laid across her knees, which may be quite comfy with regard to posture, but it is not at all efficient. Just think of the weight of a board thick enough to endure repeated hammer blows without breaking and add to that the vibration of the blows. I can't imagine that her knees would survive that for a whole day, not to mention weeks.
The more the surface resoinates, the more hammer blows you need to cut multiple layers. For eight layers of taffeta, it took me 7-8 blows on tiles over concrete, 5-6 blows on concrete slabs over gravel, and 2-3 blows on a massive concrete step sitting on a concrete wall. In case of a couple of metres of ruffle, this can make the difference between muscle ache or no muscle ache. My recommendation, therefore, is to use very massive concrete or actual rock as a subsurface.
Place a wooden board and a thick layer of paper on top of the concrete for the tool to bite into as soon as it has passed through the fabric. I believe that in period, lead or leather were used, but I haven't tried that yet. If there isn't a soft layer underneath the fabric, the tool can't bite all through the fabric.
If the piece you want to pink is something small, you should pink one layer at a time, or maybe the right and left sleeve ruffle at once. If you're pinking a couple of metres of straight ruchings, it is more efficient to fold the fabric sand punch through 4-8 layers at once. Make sure that all layers lie exactly parallel on top of each other, escpecially if the fabric is patterned. Pin the layers together to prevent them from moving, but take care not to punch through a pin.
Now you need a hammer. Use the heaviest one you have available. Place the pinking tool onto the fabric, take care not to move around too much, and then hammer as long as it takes to go through the fabric. To check whether you've gone through, keep the pinking tool in place with one hand and pull the fabric away from the back of the tool. If you can pull it clean away or if it's only a matter of a few threads, you're through. If not, strike some more blows and try again.
Never mind if a few threads still hang on. Cut them later with embroidery scissors or similar.
According to some informants, you may be able to find something like it in leather shops. Some sutlers in the US carry them. When I shopped for one, Greenmanforge (see purveyors page) had the best prices and good service. When ordering a custom-made oinking tool, don't forget to specify not only the width but also whether you want a half-, third- or whatever circle.
Be sure to never use the tool on a surface that is almost as hard or even harder than iron, lest it become dull. A humid environment isn't becoming, either, because it would rust even after a few hours. As with a knife, you should regularly use a suitably-shaped whetstone.
And what if it has become dull nevertheless? You might try a shop that sharpens scissors, knives and other tools, but I doubt that they'd be able to cope with the little scallops. The maker of my tools recommends small, ceramic whetstones as are used for wood carving tools. Someone who carves woold may be able to point you in the direction of a supplier of such whetstones, teach you how to sharpen your tool and maybe quote a shop that can sharpen tools like yours. I was told that it's most important not to change the bevel.