Is there any reason not to do laundry with bar soap?
When traveling light, is there any reason not to use standard hotel-issue bar soap to wash clothes in a hotel sink? Carrying powder laundry detergent (or worse, liquid!) seems like a big hassle if standard hand/bar soap will do an adequate job. If I go this route, are there any common clothing materials that won't stand up to this sort of washing over time?
Why do you say `or worse, liquid!`? I regularly use liquid detergent for traveling since they have a screw on cap and are very practical for use. They come in travel size and are more effective than powder detergents.
@rlesko: Mainly because the consequences if spilled are much higher than with dry soap. Air travel restrictions on liquid can be an issue, too, when not checking luggage. I realize there are ways to safely transport liquids, even in low-pressure situations found in an aircraft cargo hold, but it's just easier to transport dry substances, and easier yet to transport nothing at all--thus the question. :)
In the olden days you did do laundry with bar soap - but it was laundry bar soap - harsher and unscented. You can still get it in Mexico and probably lots of places.
I guess "hand soap" as it is (or was) usually called differs mainly by being more expensive and probably has ingredients to be less harsh on the skin, and it's usually scented.
Whether any of these extra ingredients is bad for fabrics I doubt but you never know. But being gentler on skin you can be pretty sure it's going to be gentler on stains also, so less effective on clothes.
So if the convenience of carrying fewer kinds of soap outweighs the higher price and lesser cleaning strength then sure - wash your clothes with hand soap while you're on the road. But now and then you probably want to wash it with laundry soap too.
(If you've ever tried washing your hands with laundry soap you will notice it can badly dry your skin. I made this mistake recently where the hostel bathroom didn't have hand soap but did have laundry powder. After a week or so the skin only on my hands was raspy and I realized my mistake.)
Your answer got me to look for bar-form laundry soap, and came across the apparently popular Octagon All-Purpose Soap bar (and of course a number of competitors), which would make for a useful all-purpose travel soap I suspect. Not quite as convenient as hotel soap, but more reliable and more certain to be available.