Under special rules for Craft they mention:
Tools & Equipment To make an item using Craft (alchemy), you must have alchemical equipment. If you are working in a city, you can buy what you need as part of the raw materials cost to make the item, but alchemical equipment is difficult or impossible to come by in some places. Purchasing and maintaining an alchemist's lab grants a +2 circumstance bonus on Craft (alchemy) checks because you have the perfect tools for the job, but it does not affect the cost of any items made using the skill.
Seeing as the archetypal witch uses a cauldron to mix her potions and poisons, would it be fair to say that a cauldron would count as the witch's "lab" and thus provide the +2 circumstance bonus to the check? I know you get a +4 insight bonus already with the hex... so I guess what I'm really asking is; does a witch need to lug around both a portable lab AND a cauldron to get the optimal +6 for her alchemical needs?
-=-=-=-
I am really enjoying playing a witch, but feel that Paizo can and should do more to give the class more flavour text and official hex options.
Portable Alchemical Lab only gives +1.
The regular lab at +2 is the masterwork version.
You can use the cauldron, or the lab, but not both, to do your work.
If you want to crank your plusses, you could get the Magenta Prism (cracked) Ioun Stone that lets you paste a +2 on any skill, chosen 1/day.
/cevah
Cauldron (Ex): The witch receives Brew Potion as a bonus feat and a +4 insight bonus on Craft (alchemy) skill checks.
Yes, if you want to add a circumstance bonus to the insight bonus, you will need to purchase an alchemy lab. The hex does not remove the requirement for the witch to have the appropriate tools for Craft (Alchemy): "All crafts require artisan's tools to give the best chance of success. If improvised tools are used, the check is made with a –2 penalty. On the other hand, masterwork artisan's tools provide a +2 circumstance bonus on the check." Using just the cauldron (without an alchemy crafting kit, portable alchemist's lab, or alchemist's lab), would count as improvised tools; note that a witch with the Cauldron hex can make Craft (Alchemy) checks with improvised tools as well as a non-witch with a full-blown alchemist's lab (+4 -2 = +2 for the witch, +2 for the non-witch).
Of course, once you can afford it, this makes an even better investment:
CAULDRON OF BREWING
Price 3,000 gp; Aura faint transmutation; CL 5th; Weight 5 lbs.
A cauldron of brewing looks like a fine cooking pot with four stout legs. The cauldron is capable of heating any liquid placed in it to a precise temperature (anywhere from just above room temperature to hot enough to boil salt water) and maintaining it indefinitely while still remaining only slightly warm to the touch on the outside. A cauldron of brewing provides a +5 competence bonus on Craft (alchemy) skill checks.CONSTRUCTION REQUIREMENTS
Cost 1,500 gp
Craft Wondrous Item, creator must be trained in Craft (Alchemy)