I’ve witnessed this with face creams, coconut oil, and lip balm – anything solid at room temp. if you dig a finger into the product, or run your nail against it, what comes away is soft and spreadable, rather than a hard chunk. I imagine the cell structure is changing in some way, but – what way? why does this happen?
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> I imagine the cell structure is changing in some way
Oils are not typically made of cells. Cells are for living tissues, atoms and molecules are for chemical substances like oils. A face cream or lip balm is just going to be chemicals and not tissue, living or otherwise.
> why does this happen?
Probably because it is getting warm. I hazard to guess that you have noticed that your and others’ grubby mitts are warm to the touch, maintained at a temperature higher than ambient due to our metabolism turning chemical potential energy into active biological processes. Much of that energy leaves our bodies as heat and as blood continually circulates through the tissues of our fingers it keeps them warm.
Many such creams are formulated such that they will be soft and pliable at the temperatures of the surface of the human body. This is very intentional for the reason you just described.
>I imagine the cell structure
Oils don’t have cells, and they get soft because they are melting due to your body heat. Fats and oils often have freezing points that are right around room temp or body temp. Lots of them, like coconut oil, are solid at cool room temp but liquid at body temp. So when you scoop with a finger, the solid warms up enough to melt. It only takes a few degrees since room temp is just below its freezing point.
> …if you dig a finger into the product, or run your nail against it, what comes away is soft and spreadable…
Try an experiment.
Take a plastic knife/spoon/spork/whatever and put it in the fridge/freezer for a couple minutes. Take another and put it in some warm water for a little bit.
Now take the cold spork and dig a little bit into the oil/cream/balm. Does it become soft or stay as more of a hard chunk?
Now take the warm spork (and dry it off with a towel or something) and dig a little bit into the oil/cream/balm. Does it become soft or stay as more of a hard chunk?
(SPOILERS BELOW)
If you do the little experiment above, you’ll probably “discover” that the warm spork makes the oil/cream/balm melty and smooth while the cold spork leaves it more clumpy and solid.
This is because the chunkyness/oilyness changes due to temperature! The ingredients in the oil/cream/balm have a melting point that is lower than your body temperature. Therefore, when your warm fingers (or even the somewhat-warm back of a fingernail) touch the stuff it warms up the substance and causes it to melt and become less chunky.
They’re melting.
Your body is around 98°. Those materials you’re describing have a melting point lower than 98°. They’re solids at room temperature but just barely, and they’re liquids at just above room temperature.
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