Crafting, and the limits of the rules as written

[MisterPlacebo]

I have a question on crafting that comes from an advice thread I had going. It regards this statement about crafting:
"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."
Question is, do the rules allow a character take a -2 use their stomach (ignoring questions of toxicity for the moment) to create an alchemical item such as alchemical fire (not potions). And secondarily, if yes, is does it bend/abuse the rules, or is it just a creative use of the system?

The two opinions so far are:

As long as you take the -2 there really isn't a mechanical difference between whether you use your stomach to craft the alchemist fire or whatever you have lying around.

-or-

The crafting procedures may be unspecific for individual items, but you're expected to use "common sense". You can't really manipulate materials once they're in the stomach. Most (if not all) of the work would have to be done outside the stomach.

[Diego Rossi]

You should use common sense. Improvised tools should have some relevance with the task at hand. In an emergency, you can use the excised stomach of a dead animal as an alembic to mix liquids, but the stomach of a living being isn't something that can be used to mix liquids.

The list of possible improvised tools is so long that probably we would need a book of the size of the CRB to list the possible tools for 1 crafting skill.

[Dave Justus]

The first opinion is mine, but I don't disagree at all with the second, because I don't think this is really a rules questions.

The rules say, that if you have items that can be used as improvised tools (GM would have final say if questionable) then you can make a craft check to make an item with a -2 on the roll.

If you meet those two requirements, you are good to go. If what you want to do is add fluff to that that you are making it in your stomach, that fluff is a GM call and will probably depend on the nature of the game.

If your question is, do the rules say that your stomach is a reasonable improvised tool, they don't specifically mention that, but the answer would pretty clearly be no. It isn't reasonable that you can do that, so if you didn't have anything that would reasonably be useful substitute for alchemy tools (you are in a bare room, naked with nothing but the ingredients required) then the rolls, interpreted with common sense, would say no, you can't do it.

That circumstance is going to be so incredibly rare though that it isn't really worth considering. If you have the ingredients you need you almost certainly have something that would work as improvised tools, so you will be able to make the roll at -2. Whether you can make the item is really never going to depend on whether or not your stomach would be a reasonable substitute, so it just comes down to being a fluff question.

So do the rules say you can do this: No. Is their any mechanical reason for a GM to say you can't describe it this way? Also No.