i have only done a few bowls. Seems there a lot of choices on finish. I'm sure wood choice plays a part. Most of my bowls will be cherry, walnut, maple, ash, and elm. Woods I have locally. Here is what I have or considered. What finish do you use and why?
1. Walnut Oil. I have read mixed reviews about using Mahoney oil in regard to drying. I have some, but somewhat hesitant in using this. A black light is recommended to assist in drying.
2. Danish Oil (Watco). I haven't used this on bowls, but seems it would be reasonable.
3. WOP. Doesn't seem to be the best choice for a utility bowl. Does anyone use this for bowls
3. Lacquer. Same as WOP.
4. Salad Bowl Finish. I have use this and also the Watco brand called Butchr Block Finish. Works well.
5. Mineral oil (with or without bees wax). I use this on my butcher blocks, but haven't used on a bowl.
6. Boiled Linseed oil. Never used as concerned if it would go rancid.
7. What else is there?
If I can get over my fears I will try the walnut oil on my next cherry bowl. So far I seem to like the Watco butcher block Finish, but a little costly. I don't buff or wax after applying the finish.
Based on the title of your post, I'm assuming you're looking for a finish that would be used for a food-containing bowl. The bowl would see frequent use and frequent cleaning (sponge/paper towel, warm soapy water & rinse, air dry).
Based on Bob Flexner's book, all finishes, once fully cured, are food safe--the volatiles have volatilized, but I'd take that advice with a grain of salt...
Cleaning and/or use of serving utensils will almost always wear finishes a bit. One question is how many cleanings before the finish is gone. Some folks don't bother finishing their utility bowls (with caveats added below).
I'll start backwards:
7: Epoxy resin, such as the System Three epoxies. About the only finish that will resist alcohol (e.g. if you're making a wood goblet for consuming distilled spirits). If you only rinse out the distilled spirits, I would imagine this would last practically forever. Difficult to apply in even coats, can sensitize the skin of the person who's applying the epoxy. (Not a sensitizer when fully cured).
6.5 Shellac(s). Definitely food safe ("GRAS" according to the FDA, used as a coating for medical pills, and some hard candies). Will eventually wear away under use, not really waterproof.
6.3 Tung oil (real tung oil, not "tung oil finish.") A polymerizing vegetable-derived oil. Thin coats, lots of time spent, not really waterproof.
6. BLO: Does not turn rancid--"Boiled" is a euphemism for metal additives such as Zinc that make the linseed oil polymerize faster. Thin films polymerize when in contact with oxidizers (such as air!). Multiple thin coatings, etc. Will eventually wear away, not really waterproof. There are a number of vegetable oils that polymerize when in contact with air; linseed oil, flaxseed (same thing, but if you buy flaxseed oil at the health food store, you know it's edible and contains no metal salts to accelerate polymerization).
5. Mineral oil will not polymerize. It repels water, but is not waterproof. It will want to be replenished periodically.
4. Salad Bowl Finish (such as General Finishes SBF) is basically a polyurethane, similar chemistry to the wipe-on-poly's. It's a film finish that polymerizes or cross-links when the solvent evaporates (or possibly on contact with air). Water resistant, but not waterproof, unless it's applied in numbers of layers that are ridiculously thick.
3. Lacquer: It's actually more similar to shellac than wipe-on poly. It's a resin-in-solution (the original lacquers). Modern lacquers are nitrocellulose polymers rather than tree resins, but again, they are in solution, and when the solvent evaporates, they bond through mechanical contact and Van Der Waals forces. Lacquers are generally more durable than shellacs. Not really waterproof.
3. WOP-wipe-on-poly is just a viscosity/surface-tension-modified polyurethane finish. Upon evaporation of the solvent (and possibly exposure to air), the molecules cross-link & polymerize to form a film. Not waterproof.
2. Danish oil. This is typically boiled linseed oil that's been pre-diluted with solvents such as mineral spirits, to make for easier and faster application. See BLO comments for water resistance.
1. Walnut oils. This is a polymerizing vegetable-derived oil. Mahoney's (and Dr Woodshop's) assert that they have a process that removes the glycoproteins from the oil. Allergies are based on the glycoproteins and not the fatty acid chains in the oil. Applying in thin layers (and wiping off excess), and allowing each layer to polymerize in air would have similar cosmetic results as Danish oil or BLO. Again, see comments for water resistance.
Buffing with Carnauba and/or bees wax: Carnauba and bee waxes are edible (but not the solvent carriers...). Does not make for a particularly durable or waterproof finish, but the buffing process puts a nice soft sheen on the surface.
If you weigh cosmetics and convenience: For personal use, I'd do multiple layers of walnut oil (I'm not allergic, but theoretically, Mahoney's has had the glycoproteins removed), and do a final wax buff. I'd occasionally do a re-wipe of the insides with mineral oil (butcher block oil).