Any good or substance produced by the Alchemy skill.
They are not intrinsically magical but will probably be perceived as such by the ill-informed masses.
First, put some points into the Alchemy skill. Anyone with at least Expertise 1 in this skill can create any and all Do items.
Then take one or more Master of Formulae talents and/or the Dabbler talent.
Each Master of Formulae talent grants the ability to create all petty enchantments of that type. For example, if a character learns Lotus Pollen as a Master of Formulae Talent, they learn to make all the Lotus Pollen items on the Lotus Pollen chart (ch.7, p.166).
Note that the Master of Formulae talent has a prerequisite of either the Alchemist talent or the Patron talent.
Ch.3, p.56 in the core book is wrong. You don't learn formula per rank of the skill.
Creating a petty enchantment is a use of the Alchemy skill.
Crafting use Resources called Ingredients (ch.6, p.141). Unless otherwise stated, each Petty Enchantment requires one Ingredient. Extra Ingredients can be used for bonus d20’s, just like any other Resource.
The book is very vague about the time required. The errata suggests an hour, with a Reduce Time Required Momentum spend of 2 to halve this to 30 minutes.
Success produces one use of the enchantment, with 1 extra use for each Improve Quality of Success Momentum spend of 1.
The following recipes are commonly known (and available to a Dabbler). Knowledge of other recipes will need to be found while campaigning.
Exploding Powders: Flash paper, Small Fireworks, Loud Fireworks, Large Fireworks.
Blinding Powders: (All).
Burning Liquids: Burning Liquid, Burning Alcohol, Exploding Liquor, Volatile Spirits.
Reinforced Fabric: (All).
Upas-Glass: (None).
Talismans: (All).
Lotus Pollen: (All). Note that lotus plants are very rare, so obtaining Ingredients is more difficut than other petty enchantments.
The Stygian Black recipes (ch.7, p.166) are also used for poisons from other sources.