Applying shaving gels to the face in relatively colder climes makes it very cold when applied. There is the initial few seconds of coldness upon application.
What is the ingredient that causes it and why has no one made a product that does not have this effect.
I think it’s mostly the same as anything involving compressed gas being let out of confinement.
There’s also the effect of adding a liquid to the skin. Liquids conduct heat better than air, so unless they’re heated up to be at least as warm as the skin, they immediately absorb some heat until they achieve thermal equilibrium. That’s the few seconds of coldness upon application.
I guess the effect is mostly from alcohol evaporating, although some gels also may contain menthol.
Two factors come to mind:
-you’re applying a cold mass that has good thermal conductivity. a 1/8" layer of gel on your face has more mass than a 1/8" layer of foam, and it also has better thermal conductivity; the gel will draw heat away from your skin faster, and in greater quantity, than the foam.
-Some gels are designed to turn to foam after applying them to your face. Presumably this uses heat from your skin to cause a phase change in one or more constituents of the gel. In the same way that sweating cools you on a hot day (i.e. evaporative cooling), the transformation of a liquid to a gas within the shaving gel takes even more heat out of your skin without allowing the temperature of the gel to rise very much.
I was thinking of the noble gas law, PV=nRT.
As the pressure decreases, so does T.
But the propellant isn’t dissolved in the gel; this is why the gel comes out of the can as a gel and stays that way until you smear it on your face (and thus heat it up).
If you crack open a can of shaving gel, you’ll find that the gel is contained inside a bag, and the propellant is outside the bag; it just squeezes the gel out of the bag through the can’s nozzle, the same way a pastry chef dispenses frosting.
Don’t you have better things to do than confuse people with the facts? :dubious:
Perhaps the propellant cools the gel when it moves it.
Popping nitrous?
because it contains such ingredients as сypress, menthol, etc.
More properly called the “Ideal Gas Law”. Noble gases are Helium, etc., which come closest to meeting it, but the law generally applies to many other gases in approximation.
I’m not sure that’s true; if you’ve ever pulled that little plug out of the bottom of the can, gel shoots out- there’s no bag at all, at least not in Edge products.
At any rate, the ingredients are pretty straightforward (Edge Sensitive):
The one exception is isopentane. It’s a hydrocarbon with a boiling point very near room temperature (81 F)
So they condense the isopentane and dissolve it in the rest of the ingredients, which just amount to a mixture of oils, soaps and thickeners, and aren’t materially different than canned foam.
Then, when you squirt out a little bit of gel, it’s gel, but it’s starting to expand. When you rub it on your face, you heat it up just enough to have it really expand, and you get the thick foam that the gels are known for. Not coincidentally, this phase change when you apply it to your face and it boils/expands is a pretty endothermic reaction, and makes it feel cool.
If you squirt some out and leave it, it’ll expand on its own, due to the isopentane slowly expanding and evaporating.
Then, if there’s menthol or anything like that included, it just intensifies the sensation.
Thanks, ftg.
I’ve personally torn apart a can and seen the configuration described at the link I provided. I suppose the Edge folks have figured out how to do away with the bag and save some money.
It would be interesting to dispense a large pile of gel from a room-temperature can onto a plate and then measure its temperature to see whether it has actually become colder than room temperature due to the dispensing process. If I can remember to do it this weekend, I’ll report back with results.
So I did this yesterday. I put a digital meat thermometer and a can of shaving gel in a cardboard box in the basement for about 24 hours to let the temperature stabilize; I used the box (instead of leaving them out in the open on the workbench) so that any intermittent drafts from HVAC wouldn’t induce an offset between the gel temp and the thermometer temp.
The result? The thermometer read 63.0 degrees before and after dispensing a 4" mound of shaving gel on it. Not particularly surprising, since the gel doesn’t expand when it comes out of the can; if it did, it would be foam, not gel.
I presume that the chilly temp in my basement precluded the development of foam on the surface of the mound in any reasonable time frame. Perhaps if I had done this in the bathroom with the space heater on (jacking up the temp to ~90F), I might have witnessed the gel turning to foam as it came out of the can.
The isobutane boils off at a very low temp, that alone would make it feel very cold.
The gel I used in this test (Gilette Comfort Advantage) lists the following ingredients:
Water, glycerin, palmitic acid, triethanolamine, stearic acid, isopentane, glyceryl oleate, fragrance, isobutane, sorbitol, hydroxyethylcellulose, PTFE, PEG-90M, tocopheryl acetate, PEG-23M, propylene glycol, aloe barbadensis leaf juice, blue 1.
Two points:
#1: Isobutane is listed after fragrance. Assuming the ingredients are listed in the order of their proportion in the final product (as is the case with foods), then there’s very little isobutane in it.
#2: The test I did shows that the product is the same temperature after dispensing as it was in the can. Isobutane boils at ~10F, so if the boiling of isobutane were going to cause a temperature drop, it would have happened within the first few seconds after being dispensed.
The isopentane, which boils at 80-90F, would lower the temperature after being applied to warm skin.
Note that there’s no menthol in the stuff I tested.
Do you keep your shaving gel in a bathroom medicine cabinet which is on an outside wall? And it gets cold in there?
If yes, try leaving it on the sink counter next to those fancy balls of soap no one is ever supposed to use.