A dry ounce is strictly a unit of weight, not weight per unit volume (density). For example, in SI units, a mass of about 0.02835 kg in 1g (0.2778N) is equivalent to one dry ounce.

Lest we not forget that the specific gravity of a liquid depends upon the ambient temperature. Therefore, if the TSA agent is unable to make a distinction between a weight and liquid ounce they should be provided with hydrometers so that they can quickly determine the volume of the weight ounce.

Stay the curse!

My all time favorite has to be the 4.3 oz toothpaste I was carrying around weekly for two months before it was taken. So then I was able to finally find small toothpastes at a local store (99 cents each for .85 oz). So, I am able to take a bag full of these and not one 4.3 oz container. Does this make any kind of logical sense? So, back to pealing the label off the 4.3 and putting a prescription label on it. "That is for medical purposes, I have to get the placque off my teeth." Most often it works. I just wish there were consistancies at the airports every time I travel. I have the same stuff every week and sometimes I have to explain the extra laptop battery, sometimes I get the toothpaste taken, sometimes I have to take out the extra hard drive....all at the same airport. Drives a person nuts. It is a pain to travel as it is but to add these headaches is unreal. And TSA wonders why we complain and get an attitude...stop changing the rules daily. Use logical sense, 4.3 oz toothpaste is really not that big of a difference than 3.4. The cost of those little tubes adds up and they are next to impossible to find. And no, I am not going to check the bag...then I would have another whole list of gripes....ok, off my soap box.

Sorry, I worded my response incorrectly. But a dry ounce of material--a measurement of mass (technically not of weight, but outside an academic setting, most people use them interchangeably)--the volume of one dry ounce of a given material does depend upon the denisity of that material, meaning that, as I said, one dry ounce does not have a fixed proportion to the volume across all substances.

For water, for example, a dry ounce has a volume of one fluid ounce (actually, just over 96% of a fluid ounce, but close enough here to illustrate the point). But a substance which is half as dense as water will, given one dry ounce of the substance, have a volume twice that of an equal mass of water.

(This does discount the effect of temperature sailman pointed out, of course.)

Carl. Isely - Prior to my commenting on your post let me make it clear that I am not employed by the TSA or any other government agency. Therefore I have not had the benefit of their extensive training, indoctrination, and security screening process.

Given this handicap, my comment on your post might seem naive, for which I apologize. So let me guess. Do you need the second laptop computer battery in case the one in your computer is low on electricity?

Stay the curse!

Yes considering I usually need this for my job and you can't check it in luggage. Sometimes the longer flights require one too. The point of my post was asking for some kind of consistancy and common sense.

You are referring to specific volume... the inverse of density. You are implying that a pound of feathers would occupy more volume than a pound of lead, which is of course correct. If I may hazard a guess, you probably find it a cardinal sin when someone confuses volume with mass (or weight). So do I.

The problem is that some confusion springs from a de facto 'conversion' of dry ounces to liquid ounces, using the mass and volume of water at specified pressure and temperature as the vehicle to affect the conversion. The FTC has rarely balked when such conversions were used to establish claimed weights on packaging.

Thank you for this discussion... I do find it enlightening and enjoyable :)

Do you enjoy making stuff up?

Getting back to the "acceptable quantities" quandry, would carrying on 2 x 4 oz. bottles of contact lens solution (factory sealed) be "acceptable" for a 2-week trip through Italy, seeing as I don't want to check my bag and potentially have it "misplaced"? Yes, I'm packing light for this trip!

:D I warms the cockles of my heart that one of the Kip's own people refer to it as a Kippie bag! Love the irony ^


What about flight delays? What about flight cancellations while en-route? What about having to spend the night at an airport hotel? Or worse, inside the airport because all the rooms are gone? I don't recall seeing HMS Host selling XYZ formula...because you know if they did carry it, it won't be the kind the child would need.

Agreed. Though on my last trip I saw a guy buying a RockStar energy drink for his 8-9 year old son :eek:


You know, *I* might drink from a public fountain, but no way do I use that water to make my daughter's bottle! Hell that's right up there with airplane lavatory water on "Not going to happen" meter!


Correction: Younger female TSOs tend to be the best. Younger male (20s-30), grumpy old males (>55) and grumpy old maid females (>40) seem to hassle anyone at any time, kids or not. ;) Actually, I remember a mid-40s woman at ATL screaming at the 4 year old in line behind me because he touched the sides of the WTMD with his hands! The mom was too frazzled dealing with her infant to notice that some strange woman was dressing down her son. :o Then I heard one of the other TSOs tell the screamer "...ought to be ashamed of yourself for yelling a little kid like that!" ^ Not sure what happened with them.


Actually, I've seen other FTers make reference to that single layer "rule" and I've seen & heard TSOs at different airports yammer at people that their Kippie bags were too full. I think ABQ even has a sign that says the items must fit "comfortably" in the bag.

I was taught otherwise; a dry ounce is 1/16 of a pound. A pound is a unit of force (weight); the unit of mass in the silly system is the slug (about 32lb in standard Earth gravity). Therefore a dry ounce is weight, not mass.

However people seem to say the pound is mass. But then pound-feet is not torque. Stupid "conventional" measurement unit can't even decide what it is.

no

My last 12 trips, I have not even removed the "Kippie Bag" from my carry on and it zipped right through with no questions.

In my last few flights I've carried a metal water bottle (0.5L or so). It was empty, but the TSA guys & gals never checked. Next time I might see if they catch it if I "forget" to empty it.

Good luck on that one let me know how it goes...