# CLothes Dryer Science **URL:** \ **Category:** Factual Questions\ **Created:** [July 27, 2004, 2:14pm UTC](https://boards.straightdope.com/t/clothes-dryer-science/257092 "2004-07-27T14:14:49Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Contrapuntal](https://avatars.discourse-cdn.com/v4/letter/c/e274bd/32.png) [@Contrapuntal](https://boards.straightdope.com/u/Contrapuntal)\ **Post date:** [July 28, 2004, 2:40pm UTC](https://boards.straightdope.com/t/clothes-dryer-science/257092/21 "2004-07-28T14:40:03Z")
[QUOTE=Cheesesteak] > [@](#): > > Well, if you have a dryer full of dry towels and toss in one small wet article, I think that article is going to dry pretty quick because it’s moisture will be distributed amongst the dry stuff. There is also going to be a significant amount of physical rubbing to help pull the moisture from the wet article. Everything in the dryer will fairly rapidly wind up a little bit wet, which could be good enough for government work. In order to get “fully” dry, however, you still need to heat and vaporize all that water, which will take time .That’s sort of where I was going with my premise; that moisture evaporates more quickly from a larger surface area. The question I guess would be whether the time it takes for the moisture to transfer from the wet article to the dry is sufficiently small that the increase in surface area compensates for it. > [@](#): > > One other thing to consider is the “action” the items get. Sticking one small towel in might not give you enough agitation to get it dried efficiently, then it would be worth it to throw in a couple more dry towels to get the stuff mixing well. Another good point. Something tells me that there is a point where a mixture of wet and dry is more efficient but I have to admit it is just a “feeling” and I sort of want it to be true so I do distrust it. Not that feelings count for anything anyway. ---
**Author:** ![Greywolf73](https://avatars.discourse-cdn.com/v4/letter/g/d9b06d/32.png) [@Greywolf73](https://boards.straightdope.com/u/Greywolf73)\ **Post date:** [July 28, 2004, 2:52pm UTC](https://boards.straightdope.com/t/clothes-dryer-science/257092/22 "2004-07-28T14:52:15Z")
I must add a comment that is sort of off-topic but still relevant. I have discovered a way around ironing if you are too lazy to drag out the iron and ironing board. Far less energy-efficent though. Pop the wrinkled item in the dryer with a damp cloth and turn on for about 10 minutes. Ta-Da! Instant wrinkle-removal! Anyway, my method for dealing with clothes/towels left in the dryer–I simply forget about them until the next time I need the dryer or need a clean towel, whatever comes first. When I DO need the dryer again, I simply dump the forgotten load of laundry in the middle of my bed so I will be sure to remember to fold them before I go to bed. Unless I just shove them off into a pile on the floor at 1 AM… I don’t think I’ll be receiving any awards for housekeeping any time soon. ---
**Author:** ![KP](https://avatars.discourse-cdn.com/v4/letter/k/a9adbd/32.png) [@KP](https://boards.straightdope.com/u/KP)\ **Post date:** [July 28, 2004, 3:08pm UTC](https://boards.straightdope.com/t/clothes-dryer-science/257092/23 "2004-07-28T15:08:20Z")
Actually, the energy to heat the clothing is an insignificant factor 1. It takes roughly 80 cal/g to raise water to the boiling point, but [540 cal/g](http://www.encyclopedia.com/html/section/vaporiza_TheBoilingPointandLatentHeatofVaporization.asp) to supply the Latent Heat of Vaporization that converts it to water vapor. A liquid with the same boiling point as water, but a much lower latent heat of vaporization would be much more volatile than water. 2. clothing in a dryer doesn’t ever reach the boiling point of water, but individual water molecules do, carrying off heat in the process. This is why sweating can cool you off even at a paltry 37C (98.6F) compared to the 100C boiling point of water: the hottest molecules evaporate, leaving cooler ones behind. 3. damp clothing can hold more than their own mass in water HOWEVER: the question of whether your clothes will dry faster can be solved by a simple measurement, without any math. Just monitor the Relative humidity of the air leaving the dryer (e.g. by passing it through a container with a wet towel suspended in it, and monitoring the towel’s weight). At all times when the RH is 100%, the process is proceeding as fast as it can, limited by the volume of air pumped by the fan. Only at the times when the RH is under 100% can you get an improvement. Yes, it’s terrible what a bored teenager science genius will spend a summer day doing. A mind is a terrible thing to waste. Unfortunately, I had no way to measure the absolute dryness of the clothing. I did weigh the clothing afterwards, but it turns out I’d have had to do multiple loads until I hit the exact same weight – and NO teenager is that bored-- so I can only say that any speedup for a full load was more modest than I’d hoped. However, if you just want to dry off a few things (e.g. a Boy Scout Uniform, when the carpool is coming in 12 minutes,) a big load of dry towels is just the ticket. ---
**Author:** ![Manduck](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/manduck/32/256_2.png) [@Manduck](https://boards.straightdope.com/u/Manduck)\ **Post date:** [July 28, 2004, 6:05pm UTC](https://boards.straightdope.com/t/clothes-dryer-science/257092/24 "2004-07-28T18:05:17Z")
Nobody cares about the wrinkles except me ☹ ---
**Author:** ![Contrapuntal](https://avatars.discourse-cdn.com/v4/letter/c/e274bd/32.png) [@Contrapuntal](https://boards.straightdope.com/u/Contrapuntal)\ **Post date:** [July 28, 2004, 8:16pm UTC](https://boards.straightdope.com/t/clothes-dryer-science/257092/25 "2004-07-28T20:16:14Z")
Upon reflection, a bored teenage science genius is just what this situation calls for. (You know, there might be some superhero possibilities there.) I’m not sure I follow your protocol there \*\*KP \*\* but it seems you are saying that there is some point at which a mixture of wet and dry is the most efficient. Thanks for the effort, and thanks for enabling me to continue my lazy ways. ---
**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\ **Post date:** [July 28, 2004, 9:52pm UTC](https://boards.straightdope.com/t/clothes-dryer-science/257092/26 "2004-07-28T21:52:46Z")
> [@KP](#): > > Actually, the energy to heat the clothing is an insignificant factor… Which, actually, is what I said back in Post #4. 😉 > [@KP](#): > > …2) clothing in a dryer doesn’t ever reach the boiling point of water, but individual water molecules do, carrying off heat in the process. This is why sweating can cool you off even at a paltry 37C (98.6F) compared to the 100C boiling point of water: the hottest molecules evaporate, leaving cooler ones behind. You can’t really talk about “temperature” when discussing individual molecules. The temperature of a sample of water is related to the average kinetic energy of the molecules in the sample. You can, therefore, meaningfully discuss the kinetic energy of individual molecules, but you cannot meaningfully describe individual molecules as being “hotter” or “colder.” ---
**Author:** ![spingears](https://avatars.discourse-cdn.com/v4/letter/s/ebca7d/32.png) [@spingears](https://boards.straightdope.com/u/spingears)\ **Post date:** [July 28, 2004, 10:07pm UTC](https://boards.straightdope.com/t/clothes-dryer-science/257092/27 "2004-07-28T22:07:39Z")
> [@KP](#): > > 1. clothing in a dryer doesn’t ever reach the boiling point of water, but individual water molecules do, carrying off heat in the process. This is why sweating can cool you off even at a paltry 37C (98.6F) compared to the 100C boiling point of water: the hottest molecules evaporate, leaving cooler ones behind. > However, if you just want to dry off a few things (e.g. a Boy Scout Uniform, when the carpool is coming in 12 minutes,) a big load of dry towels is just the ticket. Correction Please. Individual molecules of water evaporate at the bulk temperatue of the towels, not at 100C. An open pan of water evaporates, just as sweat does, at whatever temperature it is at as well as the moisture in the towels. It is impossible for molecules of water to exist at a temperature higher than the bryer temperature. ---
**Author:** ![BiblioCat](https://avatars.discourse-cdn.com/v4/letter/b/ed8c4c/32.png) [@BiblioCat](https://boards.straightdope.com/u/BiblioCat)\ **Post date:** [July 28, 2004, 10:29pm UTC](https://boards.straightdope.com/t/clothes-dryer-science/257092/28 "2004-07-28T22:29:31Z")
> [@Manduck](#): > > If the towels have been sitting in the dryer all day, they will be all wrinkly. If you leave them in the dryer when you add the wet stuff, the wrinkles will be fluffed out again. I do towels last, so I can put them in the dryer and leave them to fold the next day. How wrinkled do **your** towels get? Mine don’t get wrinkled. Besides, when you fold them, any wrinkles go away. I bet you’re one of those freaks 😉 who irons sheets, too, aren’t you? ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [July 28, 2004, 11:43pm UTC](https://boards.straightdope.com/t/clothes-dryer-science/257092/29 "2004-07-28T23:43:51Z")
You people own more than one towel? ---
**Author:** ![spingears](https://avatars.discourse-cdn.com/v4/letter/s/ebca7d/32.png) [@spingears](https://boards.straightdope.com/u/spingears)\ **Post date:** [July 28, 2004, 11:48pm UTC](https://boards.straightdope.com/t/clothes-dryer-science/257092/30 "2004-07-28T23:48:50Z")
The mixing of damp and dry towels in dryer will slow the drying time by impeding the flow of air through the dryer. Why dry something already dry? ---
**Author:** ![The\_Flying\_Dutchman](https://avatars.discourse-cdn.com/v4/letter/t/9fc348/32.png) [@The\_Flying\_Dutchman](https://boards.straightdope.com/u/The_Flying_Dutchman)\ **Post date:** [July 29, 2004, 2:50am UTC](https://boards.straightdope.com/t/clothes-dryer-science/257092/31 "2004-07-29T02:50:09Z")
Okay, I’m back now so lets continue your education. I believe that you now agree with me that a dryer stuffed with dry towels will not hasten the time it takes to dry a wet tea towel straight out of the washing machine. You do wonder however if one dry bath towel might make a positive difference. Okay then, lets start a graph of dryer time vs number of dry towels used in order to dry a wet tea towel. You must admit that over a short range of 4 or 5 dry towels we are bound to see a somewhat linear function, (that is a straight line). Have you ever seen a real life mathematical function that reverses direction between the independant variable 0 and 1? I haven’t. My suspicion is that overall dryer time vs number of dry towels to dry a tea towel is somewhat exponential. After all, if the towels become more and more restricted from tumbling, the vehicle for transporting the moisture out of the dryer can be severely restricted from contact with the wet tea towel to the point where it might take days to dry and burn out the motor. Yet there is nothing to suggest a complete reversal approaching zero. Perhaps a dry hankerchief might be more effective? I don’t think so. I suspect that in the very short term, a transference of moisture from the tea towel to the other towels is certain to take place, however the dryer time overall is _primarily_ a function of the initial quantity of moisture , and if given free access to the warm air vehicle for transference out of the dryer, the inert mass (dry towels) will have little effect. ---
**Author:** ![glilly](https://avatars.discourse-cdn.com/v4/letter/g/48db29/32.png) [@glilly](https://boards.straightdope.com/u/glilly)\ **Post date:** [July 29, 2004, 4:11am UTC](https://boards.straightdope.com/t/clothes-dryer-science/257092/32 "2004-07-29T04:11:03Z")
Hmm…I have done some mixed dryer loads and checked them partially into the cycle, though for unrelated reasons. _The dry cloth had picked up very little of the moisture._ I’m willing to concede that this could be because the moisture that transfered evaporated almost immediately. The additional material is more likely to impede the contact between the relatively dry hot air and the moisture-laden laundry, thereby slowing the evaporation rate. That’s my guess. But take it with a grain of salt as I am loaded 🆒 . ---
**Author:** ![Contrapuntal](https://avatars.discourse-cdn.com/v4/letter/c/e274bd/32.png) [@Contrapuntal](https://boards.straightdope.com/u/Contrapuntal)\ **Post date:** [July 29, 2004, 1:52pm UTC](https://boards.straightdope.com/t/clothes-dryer-science/257092/33 "2004-07-29T13:52:19Z")
[QUOTE=grienspace] > [@](#): > > Okay, I’m back now so lets continue your education .I like to think that my education continues more or less constantly. 😉 > [@](#): > > I believe that you now agree with me that a dryer stuffed with dry towels will not hasten the time it takes to dry a wet tea towel straight out of the washing machine .Yes. > [@](#): > > Okay then, lets start a graph of dryer time vs number of dry towels used in order to dry a wet tea towel. You must admit that over a short range of 4 or 5 dry towels we are bound to see a somewhat linear function, (that is a straight line). Have you ever seen a real life mathematical function that reverses direction between the independant variable 0 and 1? I haven’t. I am unclear on this. I had just enough math in college to satisfy an English major (well I had some grad level statistics) but it was 15 years ago. > [@](#): > > My suspicion is that overall dryer time vs number of dry towels to dry a tea towel is somewhat exponential. After all, if the towels become more and more restricted from tumbling, the vehicle for transporting the moisture out of the dryer can be severely restricted from contact with the wet tea towel to the point where it might take days to dry and burn out the motor. Yet there is nothing to suggest a complete reversal approaching zero. Perhaps a dry hankerchief might be more effective? I don’t think so. This is unclear as well. It seems to me that towels get less constricted as they dry, not more. I have, however, taken out a dry shirt with a wet sock stuck in the sleeve, so I see your point. > [@](#): > > I suspect that in the very short term, a transference of moisture from the tea towel to the other towels is certain to take place, however the dryer time overall is _primarily_ a function of the initial quantity of moisture , and if given free access to the warm air vehicle for transference out of the dryer, the inert mass (dry towels) will have little effect This has the ring of truth about it. Like I said, I was looking for a way to justify my laziness. So you don’t think that throwing one dry towel in with my favorite Hawaiian shirt ( just those two items in the dryer) will speed the process at all? ---
**Author:** ![spingears](https://avatars.discourse-cdn.com/v4/letter/s/ebca7d/32.png) [@spingears](https://boards.straightdope.com/u/spingears)\ **Post date:** [July 29, 2004, 4:01pm UTC](https://boards.straightdope.com/t/clothes-dryer-science/257092/34 "2004-07-29T16:01:36Z")
> [@trandallt](#): > > .I like to think that my education continues more or less constantly. 😉 > This has the ring of truth about it. Like I said, I was looking for a way to justify my laziness. So you don’t think that throwing one dry towel in with my favorite Hawaiian shirt ( just those two items in the dryer) will speed the process at all? Why, in the name of common sense, gives you any basis for thinking a dry towel added to a wet one will make any difference in drying time over one wet towel? Wet two towels with a carefully measured amount of water that they can absorb completey. Dry one by itself and the other one with a matching dry one. check the drying times for each, then report back to the SDMB’s. (This is truly and educational exercise, if you want education.) ---
**Author:** ![CrazyCatLady](https://avatars.discourse-cdn.com/v4/letter/c/dfb087/32.png) [@CrazyCatLady](https://boards.straightdope.com/u/CrazyCatLady)\ **Post date:** [July 29, 2004, 6:22pm UTC](https://boards.straightdope.com/t/clothes-dryer-science/257092/35 "2004-07-29T18:22:31Z")
> [@trandallt](#): > > . So you don’t think that throwing one dry towel in with my favorite Hawaiian shirt ( just those two items in the dryer) will speed the process at all? No, it will not. And I have to wonder why such an item would need to dry faster, really. Most Hawaiian shirts are made of lightweight rayon or a rayon/cotton blend and dry incredibly quickly anyway. You could toss the shirt in by itself right before you hop in the shower, and it would be dry by the time you got out of the shower and put your undies on. How much faster would you need it, practically speaking? ---
**Author:** ![brianj16426](https://avatars.discourse-cdn.com/v4/letter/b/dbc845/32.png) [@brianj16426](https://boards.straightdope.com/u/brianj16426)\ **Post date:** [July 29, 2004, 8:42pm UTC](https://boards.straightdope.com/t/clothes-dryer-science/257092/36 "2004-07-29T20:42:06Z")
One of the best investments I have recently made was purchasing a new washer and dryers… Yes dryers - two in fact. My reasoning went as follows: a load of laundry takes about 20-35 minutes to wash the same load will take 50-70 minutes to dry by combining one washer and two dryers they can all be used at near full efficiency. My wife loves it, she says it’s like going to the laundromat… :dubious: Just my two cents… ---
**Author:** ![Cheesesteak](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cheesesteak/32/3694_2.png) [@Cheesesteak](https://boards.straightdope.com/u/Cheesesteak)\ **Post date:** [July 29, 2004, 8:48pm UTC](https://boards.straightdope.com/t/clothes-dryer-science/257092/37 "2004-07-29T20:48:24Z")
> [@spingears](#): > > Why, in the name of common sense, gives you any basis for thinking a dry towel added to a wet one will make any difference in drying time over one wet towel? I think the general idea is to “spread” the moisture around so it has a larger surface area, thus drying faster. Kind of like spreading a puddle of water so it dries in the sun. I don’t know if it would actually work, but the concept is fairly straightforward. ---
**Author:** ![Alessan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alessan/32/465_2.png) [@Alessan](https://boards.straightdope.com/u/Alessan)\ **Post date:** [July 29, 2004, 9:02pm UTC](https://boards.straightdope.com/t/clothes-dryer-science/257092/38 "2004-07-29T21:02:42Z")
If dry towels help the drying process, how come nobody’s ever designed a dryer with an absorbant inner lining? All it would take would be to glue a towel-like cloth over the inside of the drum, and to poke some holes for the steam. ---
**Author:** ![Contrapuntal](https://avatars.discourse-cdn.com/v4/letter/c/e274bd/32.png) [@Contrapuntal](https://boards.straightdope.com/u/Contrapuntal)\ **Post date:** [July 29, 2004, 9:09pm UTC](https://boards.straightdope.com/t/clothes-dryer-science/257092/39 "2004-07-29T21:09:01Z")
> [@Cheesesteak](#): > > I think the general idea is to “spread” the moisture around so it has a larger surface area, thus drying faster. Kind of like spreading a puddle of water so it dries in the sun. I don’t know if it would actually work, but the concept is fairly straightforward. Actually that was the idea that prompted my question, but ye best tred lightly here **Cheesesteak** if ye have any fear of the [the Pit!](http://boards.straightdope.com/sdmb/showthread.php?t=268873) ---
**Author:** ![spingears](https://avatars.discourse-cdn.com/v4/letter/s/ebca7d/32.png) [@spingears](https://boards.straightdope.com/u/spingears)\ **Post date:** [July 29, 2004, 9:42pm UTC](https://boards.straightdope.com/t/clothes-dryer-science/257092/40 "2004-07-29T21:42:18Z")
> [@Cheesesteak](#): > > I think the general idea is to “spread” the moisture around so it has a larger surface area, thus drying faster. Kind of like spreading a puddle of water so it dries in the sun. I don’t know if it would actually work, but the concept is fairly straightforward. Most washers, but maybe not yours, spin or centrifuge the, clothes (towels) to extract most of the liquid. There is nothing to spread. See the post “Clothes Dryer PSEUDO-Science” in the basement. [Previous page](https://boards.straightdope.com/t/clothes-dryer-science/257092.md?page=1) [Next page](https://boards.straightdope.com/t/clothes-dryer-science/257092.md?page=3)