A problem with recipes from the 18th century is that they often don’t give you proper measurements. Take “some” of one thing and “to you liking” the next. I wouldn’t be surprised if people back then had a good idea how much that represented so that there wasn’t a need to write it down exactly. And even when measurements are given, well, it wasn’t until the 19th century that such things were standardized, so an ounce may not really have been an ounce… As most of my recipes were published in England I will stick to these measurements and weight units, as they seem to have been the ones used in the 18th century:
1 pound = 373
1 ounce = 31.1 g
1 drachm (dram) = 3.89 g
1 scruple = 1,296 g
1 grain = 64, 8 mg
1 liq. pint = 473 ml
1 fluid ounce = 29, 6 ml
1 fluid dram = 3, 7 ml
1 fluid scruple = 1.23 ml
1 minim = 0,062 ml
So, where to buy all the odd things that go into an 18th century beauty recipe. A bit of here, there and everywhere, actually. Here is where I have had luck:
Food stores The everyday, ordinary kind can provide a few useful things, mainly in the spice and the bakery sections.
Health food stores Usually stock almond and jojoba oils as well as essential oils.
Art stores For loose pigments as well as resins and bees wax.
Exotic food stores I have found spices and rosewater, but depending on store I’m sure they can yield even more interesting things.
Online Most things can be found on the Net.
In general, when looking for ingredients, it can pay to look at unusual places. Things that were used for beauty recipes back then may very well be in use today too, but perhaps for other things.