Loc: Sandpoint, Idaho, USA
Does anyone know of a truly odorless soap in bar form? I have a hand-washing system in camp where I put a small bar of soap in a nylon stocking and hang it in a tree or bush next to a small reservoir of water. Ideally I'd like to have the soap completely odorless so as not to attract bears or other critters. I know that there are soaps that supposedly remove human scent (e.g., "Dead Down Wind"), but I think the soaps themselves are scented.
Loc: Gateway to Columbia Gorge
Since soap--even "biodegradable" soap--is toxic to much aquatic life, especially amphibians and invertebrates, I never take any. If you insist on using it, make sure you are several hundred feet from any water source, including dried up seasonal watercourses.
You can scrub your hands with sand or gravel and water to remove dirt, and then use hand sanitizer. That's what I do.
All soap contains animal or vegetable fats, whose odor may not be apparent to you, but will definitely be apparent to a bear, raccoon or other interested animal. Their sense of smell is many times stronger than a human's.
May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey
Loc: Portland, OR
The advice to keep soap use to none or the absolute minimum, and to keep it far from any water source is good advice. As for a completely "odorless" bar soap so that bears will not be attracted to it, keep in mind that a bear's sense of smell is at least ten times better than a bloodhound.
All bar soap will have some kind of lipids (fat) as its main ingredient and all of them will have a smell that a bear could detect very easily, no matter what our noses can detect. Any bear that is willing to enter your campsite will take the time to investigate your hanging soap.
Whether a bear will be enticed enough to enter your campsite will depend entirely upon how the bear feels about humans. Some bears are human-habituated and do not associate us with danger, but with FREE EATS! Other bears think humans are to be avoided at all costs. Most of this will depend on the history between humans and bears in the location where you camp. The soap itself is unlikely to be a decisive factor.
I usually bring a tiny eye drop bottle of unscented Dawn liquid detergent. One or two drops is all it takes for just about anything. Other options included Dr. Bronners unscented liquid or bar or Clearly Natural unscented bar. These are vegetable based and the Clearly Natural is glycerin based. I use both at home. The Dawn gives the most bang for the buck, and seems to be the least toxic to critters. So little is needed to do the job.
I used to make bar soap. It's quite fun. You mix fats with sodium hydroxide (NaOH). Since sodium hydroxide is a very strong base and quite corrosive to skin it is common practise to use more fat than the saponification reaction requires theoretically. This leaves left-over unreacted fat in the product. This is always the case. All bar soap contains traces of oils. Which I assume bears can smell. Then again, the traces might be comparable to the smell of you farting your bean chili at night so maybe it can be neglected and you can just keep it in your tent.
Baking soda is an interesting alternative to soap for many applications. The stuff is really cool. I wrote an article about it here.
Now here's the question: is unscented hand sanitizer a bear concern? Should it be kept in a bear hang as well?
First off, soap in streams and lakes is a big pet peeve of mine. Absolutely, no washing with soap anywhere the residue could potentially flow into streams or lakes. This could be 100 feet away or 300+ feet away- pay attention to drainage.
I would not worry about unscented or not. Unless you are out for a long time, all your clothing and you will have residual soap smells and you will always have small residual food smells on you. The small bit of soap you use to wash hands is not a big factor.
I take the Dove dry-foaming makeup removers. There is very little soap in each cloth (I cut them in half and only use one half per day). I wash hands and face at night so I do not smell like a fish. I feel that smelling like scented soap is better than smelling like food. The wipes are scented so they go inside the bear canister at night.