For instance, let’s say one morning I drink a cup of coffee for breakfast and the next day I eat a cup of scrambled eggs. Assuming the same level of physical activity, roughly how long would it take a typical person’s stomach to empty? Is the difference related more to the consistency of the different substances? or the caloric value?
Liquids are easy to define but “solids” are a continuum, from something like soupy mashed potatoes to a big chunk of half-chewed meat, so it’s hard to give you firm numbers. Here’s a fairly nice write-up on gastric motility:
http://www.vivo.colostate.edu/hbooks/pathphys/digestion/stomach/motility.html
From that cite: "Liquids readily pass through the pylorus in spurts, but solids must be reduced to a diameter of less than 1-2 mm before passing the pyloric gatekeeper. Larger solids are propelled by peristalsis toward the pylorus, but then refluxed backwards when they fail to pass through the pylorus - this continues until they are reduced in size sufficiently to flow through the pylorus. "
Further down that article is a link to a second one which might also help: Gastrointestinal Transit: How Long Does It Take?
From that cite: “The discussion above should help to explain why it is difficult to state with any precision how long ingesta remains in the stomach, small intestine and large intestine.”
The shorter answer is that a cup of coffee might empty in minutes; some chunks of half-chewed ham eaten with the eggs might take several hours to get digested enough to pass into the small intestine. I am not aware that “caloric value” makes a difference, but size and consistency of what is ingested does, and some foods have a direct effect on motility, either increasing or decreasing it. Liquids pass readily and if you drink an amount large enough to wake up the stomach, so to speak, you’ll start to get little spurts of that liquid passing into the duodenum immediately. If you gulp down Thanksgiving dinner, along with something that slows down gastric emptying (such as a bottle of wine), you might need to go lie on the couch a few hours til the stomach fully emptys. This is not related so much to caloric content as it is to the time needed to break everything down and send 'er downstream.
empties
missed window. It’s tough to be the CP w/ OCD to boot.
Thanks for the great response. Those links are very informative; they even pre-emptively answer what would have been my next question about indigestible items.
Here’s one for you: You can’t drink a gallon of milk in an hour. The stomach will not empty fast enough.
I think this is akin to “a duck’s quack doesn’t echo.” Oft repeated, never cited, and makes no sense with regards to anatomy and physiology. As mentioned above, liquids pass through the pyloric sphincter without any mechanical processing from the stomach, and milk is mostly water.
In fact, the internet being the internet, of course someone’s done it, and documented the process.
Googling this led me to YouTube where a disturbing number of college kids have filmed themselves trying and failing. Why can’t they just stick with beer? 
ETA: there seem to be a lot more failures than successes documented out there.
I think it’s akin to “damn, some liquids don’t exactly wash right through me like I thought they would”. It’s an education in digestion.
But 90% of digestion happens in the small and large intestine, not the stomach. The stomach breaks things up and adds in some enzymes and acids. It shouldn’t be doing anything much with milk at all, except absorbing some of the water in it and squirting the rest through the pyloric sphincter.
Well, unfortunately for lactose intolerant and dairy-allergy folks, these thoughts don’t include all the details (I wish it did for my sake).
The main ingredients that prevent milk from passing quickly through are sugars like lactose and milk proteins, like casein. Lactose must be digested by lactase, an enzyme that specifically breaks down that type of sugar. Lactose intolerant people like myself don’t produce enough lactase, and thus we get stomach cramps, bloating, etc.
Casein is a difficult protein to digest in general (it’s used as an ingredient in some glues), and again, the stomach produces enzymes to start breaking down the protein. Bodies with dairy allergies see casein as a foreign invader, and hence the cramping, flu-like symptoms, etc.
Those are just TWO components of milk, but there are many other types of protein and ingredients that need to be worked on by the stomach before it goes into the intestines. Water is just water (most of the time), so it easily passes through.
I wouldn’t think about digestion in terms of percentages, since it depends on what aspect of digestion you’re talking about and what you’ve consumed. Lately I try to remember that a good portion of digestion happens in your mouth, so I try to chew more since I’m a quick eater. I also drink liquids slower so I can get hydrated & get the nutritional benefits through my tissue lining (mouth, throat, stomach, small intestine, etc.).
If you’re not sure what I’m talking about, think about sublingual vitamin tablets that get absorbed directly into your bloodstream through the capillaries of your tongue and cheeks. Or, any chemical for that matter - drugs, recreational or otherwise, go to your bloodstream faster through the mouth since it doesn’t have to pass through the stomach or lungs (I learned this in my college neurochem class). But keep in mind that most medications can’t be taken sublingually because they might be absorbed incompletely or erratically…plus they might taste bad.
Also, the intestines are where most of your minerals are absorbed, so make sure you have a healthy colon! Hope this helps! I set up an account on this board just to answer this question, haha.
Something of a side track, but do liquids HAVE to pass through the pylorus? This might be one of those bio-legends, 
but I have heard that water (and only water) can be absorbed into the human bloodstream through the lining of the stomach. So the non-water content of coffee might have to pass further down the digestive tract, but surely much of its volume, (osmotic pressure permitting) could be emptied more quickly?
Looking at Chief Pedant’s links, there is another page that talks about nutrient density, which is apparently a significant factor in liquid meals and explains the milk issue:
*However, if the fluid is hypertonic or acidic or rich in nutrients such as fat or certain amino acids, the rate of gastric emptying will be considerably slower and non-exponential. Indeed, the rate of gastric emptying of any meal can be predicted rather accurately by knowing its nutrient density. Nutrient density is sensed predominantly in the small intestine by osmoreceptors and chemoreceptors, and relayed to the stomach as inhibitory neural and hormonal messages that delay emptying by altering the patterns of gastric motility. The presence of fat in the small intestine is the most potent inhibitor of gastric emptying, resulting in relaxation of the proximal stomach and diminished contractions of the distal, “gastric grinder” - when the fat has been absorbed, the inhibitory stimulus is removed and productive gastric motility resumes. *
http://www.vivo.colostate.edu/hbooks/pathphys/digestion/stomach/emptying.html
Thus, it should be easier to drink a gallon of skim milk in an hour than a gallon of whole milk.
In addition, both the acid in the stomach and the action of the proteases in the stomach will make the milk curdle - it will not remain liquid.
Wrong, i did it and posted about it on this message board several years ago. it is also something I would rather not do again, but keep in mind that I tend to drink a gallon of water or more in a normal day.
if you start with the stomach empty, and sip the milk pretty constantly it can be done. If you try swilling it or chugging it, you tend to overload. Slow and steady works.
The way I heard it was, you can’t drink a gallon of milk in a half hour and hold it down for an hour.
I saw a guy try this and fail explosively at it. Also, I once participated in a drinking game called the “Hour of Power” in which one must drink a shot of beer a minute for an hour - it adds up to something just shy of a gallon. Nobody could do it. I figured a gallon in half an hour was physiologically impossible.
Then I met a guy who was a total beer-sot - a case a night, easy. I mentioned the milk thing to him and he shrugged, pulled a full gallon of milk from the fridge, and downed it not in half an hour but in about one minute in a series of three or four tremendous guzzles, straight from the container. I remember seeing his stomach bulge out noticeably. He then retired for the evening. This gentleman was a former assistant attorney general for the great State of Virginia.
To correct myself: I learned that the lactase enzyme is actually released in the intestine, not in the stomach. But the other post about milk curdling and it no longer being a liquid makes perfect sense. Thanks!