# What would cause a coffee cup to give off sparks when smashed? **URL:** \ **Category:** Factual Questions\ **Created:** [April 21, 2023, 5:07am UTC](https://boards.straightdope.com/t/what-would-cause-a-coffee-cup-to-give-off-sparks-when-smashed/983004 "2023-04-21T05:07:20Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Smapti](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/smapti/32/17938_2.png) [@Smapti](https://boards.straightdope.com/u/Smapti)\ **Post date:** [April 21, 2023, 5:07am UTC](https://boards.straightdope.com/t/what-would-cause-a-coffee-cup-to-give-off-sparks-when-smashed/983004/1 "2023-04-21T05:07:20Z")
This evening, I went to a rage room in Seattle. For those unfamiliar with this relatively new business model, it’s an establishment where they give you a milk crate full of old bottles and plates and home furnishings and the like, put you in a concrete room with an assortment of melee weapons, and let you smash stuff for 10 or 15 minutes. > **[Rage room](https://en.m.wikipedia.org/wiki/Rage_room)** > > A rage room, also known as a smash room or anger room, is a room where people can vent their rage by destroying objects. Firms offer access to such rooms on a rental basis. Statistics show that most customers are women. It is not effective or appropriate for people with anger management issues. > Rage rooms may include living room and kitchen replicas with furnishings and items such as televisions and desks. Clients may be allowed to bring their own possessions to destroy. > The first rage rooms ... It was great fun to just be able to break stuff without consequences and work up some adrenalin while letting off steam. They had a selection of golf clubs, baseball bats, and other implements of destruction, but I wound up sticking with a sledgehammer for most of my time, and I noticed something odd. My basket included a couple of ceramic coffee cups, the kind you’d buy as souvenirs from gift shops. Each time I broke one of those with the sledgehammer, it literally shot off at least a dozen or so sparks as it shattered. Thankfully none of them were substantial enough to ignite the plywood walls or the rubber mat, but it left me pretty astonished that it happened at all. What’s the physical process going on there that’s causing those sparks? Does the ceramic or the head of the hammer have some unique chemical property that produces more heat than breaking a glass bottle or a picture frame or a baking pan? I tried Googling it but all I got was a bunch of links about why you shouldn’t microwave metal. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [April 21, 2023, 5:23am UTC](https://boards.straightdope.com/t/what-would-cause-a-coffee-cup-to-give-off-sparks-when-smashed/983004/2 "2023-04-21T05:23:53Z")
Ceramic is extremely hard. Hard enough to cut tiny slivers of steel off of the hammer face. When those slivers are cut, enough heat is generated to ignite them. It’s the same principle as a grinding wheel throwing sparks when sharpening a knife, just not as intense. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [April 21, 2023, 7:30am UTC](https://boards.straightdope.com/t/what-would-cause-a-coffee-cup-to-give-off-sparks-when-smashed/983004/3 "2023-04-21T07:30:43Z")
It’s also not that uncommon for clay bodies to contain a fair bit of iron - usually in the form of oxides, but for a reduction-fired piece, the iron can be in the form of metallic particles. I think hard stuff vs steel hammer is probably the most likely and common scenario, but I reckon you could sometimes also see sparks if you smash an iron rich clay object with a wooden bat. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [April 21, 2023, 11:35am UTC](https://boards.straightdope.com/t/what-would-cause-a-coffee-cup-to-give-off-sparks-when-smashed/983004/4 "2023-04-21T11:35:32Z")
Nothing to add to the source of the sparks beyond pointing out that each bit of glowing metal is very, very small and the total energy available in an impact from a strong dude wielding a sledgehammer is very large. Easy to get a lot of heat added to a small area which leads to a yuge temperature rise. Quoting from the wiki’s lede: > A rage room, also known as a smash room or anger room, is a room where people can vent their rage by destroying objects. … As the article gently suggests, I think that in many (most?) cases they misplaced the word “vent” there and really mean “practice”. I’m not sure that at the margin encouraging highly frustrated people to learn to enjoy breaking stuff is all that good for the world. Or the safety of their roommates. Although when has that consideration ever stopped a profitable business idea? I’m _not_ suggesting our dear @Smapti would be so motivated, but I’m _real_ skeptical of the next person in line. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [April 21, 2023, 12:59pm UTC](https://boards.straightdope.com/t/what-would-cause-a-coffee-cup-to-give-off-sparks-when-smashed/983004/5 "2023-04-21T12:59:47Z")
Yeah, I was sort of disappointed to learn that these places exist, but things like it have been around a while - I remember ‘crockery smash’ attractions at fairs - same sort of idea as coconut shy, but smashing plates with wooden balls instead of trying to knock down glued-on coconuts. (although I think the plates in that case were unfired green clay so it might be the proprietors just gathered up the pieces and recycled them back into the next lot of plates) ---
**Author:** ![Bosda\_Di\_Chi\_of\_Tricor](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bosda_di_chi_of_tricor/32/16845_2.png) [@Bosda\_Di\_Chi\_of\_Tricor](https://boards.straightdope.com/u/Bosda_Di_Chi_of_Tricor)\ **Post date:** [April 21, 2023, 1:04pm UTC](https://boards.straightdope.com/t/what-would-cause-a-coffee-cup-to-give-off-sparks-when-smashed/983004/6 "2023-04-21T13:04:37Z")
I recall that crystalline materials, when breaking, emit sparks. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [April 21, 2023, 1:13pm UTC](https://boards.straightdope.com/t/what-would-cause-a-coffee-cup-to-give-off-sparks-when-smashed/983004/7 "2023-04-21T13:13:44Z")
> [@Bosda\_Di\_Chi\_of\_Tricor](#): > > I recall that crystalline materials, when breaking, emit sparks. I’m interested to hear if this is a possibility. Those sparks can be a result of a piezoelectric effect, an electrical discharge as opposed to glowing bits of material. As kids we would throw little rocks at large pieces of quartz to see the sparks, although now I don’t know if those were electrical sparks or something in the smaller rocks or impurities in the quartz. ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [April 21, 2023, 1:17pm UTC](https://boards.straightdope.com/t/what-would-cause-a-coffee-cup-to-give-off-sparks-when-smashed/983004/8 "2023-04-21T13:17:24Z")
> [@TriPolar](#): > > I’m interested to hear if this is a possibility. Those sparks can be a result of a piezoelectric effect, an electrical discharge as opposed to glowing bits of material. This also happens when you eat Mentos. Try chewing one in the dark while looking in the mirror sometime. ETA: Now that I look for it I don’t find anything specifically about Mentos, but [Wintergreen Lifesavers do.](https://recipes.howstuffworks.com/question505.htm) ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [April 21, 2023, 1:30pm UTC](https://boards.straightdope.com/t/what-would-cause-a-coffee-cup-to-give-off-sparks-when-smashed/983004/9 "2023-04-21T13:30:56Z")
I recalled that right after posting. As your cite points out that is Triboluminescence, another effect that seems most likely as the source of sparks from hitting a block of quartz with random rocks. Now I’m curious to find out if that’s related to the piezoelectric effect used to ignite gas fueled devices, and novelty shockers, among some other functions. ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [April 21, 2023, 2:16pm UTC](https://boards.straightdope.com/t/what-would-cause-a-coffee-cup-to-give-off-sparks-when-smashed/983004/10 "2023-04-21T14:16:41Z")
> [@LSLGuy](#): > > I’m not sure that at the margin encouraging highly frustrated people to learn to enjoy breaking stuff is all that good for the world. Or the safety of their roommates. I remember a story from a friend of mine who’s college roomate got frustrated with my friend’s printer and threw it out a window. I believe he paid for it without having to be asked, hopefully it was worth it for him. (This was back in the early 1990s when printers weren’t basically single-use disposables cheaper than their ink.) ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [April 21, 2023, 2:19pm UTC](https://boards.straightdope.com/t/what-would-cause-a-coffee-cup-to-give-off-sparks-when-smashed/983004/11 "2023-04-21T14:19:34Z")
> [@TriPolar](#): > > Those sparks can be a result of a piezoelectric effect, an electrical discharge as opposed to glowing bits of material. That’s what I thought. Did some googling on it before making a contrarian post, but couldn’t dig up any mention of breaking ceramics causing piezoelectric sparks. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [April 21, 2023, 2:31pm UTC](https://boards.straightdope.com/t/what-would-cause-a-coffee-cup-to-give-off-sparks-when-smashed/983004/13 "2023-04-21T14:31:58Z")
> [@Darren\_Garrison](#): > > That’s what I thought. Did some googling on it before making a contrarian post, but couldn’t dig up any mention of breaking ceramics causing piezoelectric sparks. Never heard of ceramic material doing that and we have some confirmation of triboluminescence as the reason from new Doper @HannaJ. Seems to be a more likely explanation if it’s not hot bits of impurity in the material or hot bits of hammer. Hitting quartz could cause piezoelectric discharge but I think triboluminescence is a better explanation for hitting a very large chunk of quartz with a smaller rock. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [April 21, 2023, 2:34pm UTC](https://boards.straightdope.com/t/what-would-cause-a-coffee-cup-to-give-off-sparks-when-smashed/983004/14 "2023-04-21T14:34:03Z")
Are bots allowed to post here? ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [April 21, 2023, 2:35pm UTC](https://boards.straightdope.com/t/what-would-cause-a-coffee-cup-to-give-off-sparks-when-smashed/983004/15 "2023-04-21T14:35:19Z")
Good question. How about AIs? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [April 21, 2023, 2:40pm UTC](https://boards.straightdope.com/t/what-would-cause-a-coffee-cup-to-give-off-sparks-when-smashed/983004/16 "2023-04-21T14:40:25Z")
No way. Triboluminescence doesn’t make _sparks_… i.e. - flying, glowing embers. It’s also particularly faint. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [April 21, 2023, 2:46pm UTC](https://boards.straightdope.com/t/what-would-cause-a-coffee-cup-to-give-off-sparks-when-smashed/983004/17 "2023-04-21T14:46:38Z")
Crummy video - but you can see a few sparks here: [hammer sparks - YouTube](https://www.youtube.com/watch?v=VQK5KfUt8CM) ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [April 21, 2023, 2:48pm UTC](https://boards.straightdope.com/t/what-would-cause-a-coffee-cup-to-give-off-sparks-when-smashed/983004/18 "2023-04-21T14:48:19Z")
> [@beowulff](#): > > No way. > Triboluminescence doesn’t make _sparks_… i.e. - flying, glowing embers. > It’s also particularly faint. Yes, sparks could mean either an electrical discharge or hot glowing bits of material. Would hitting a large chunk of quartz with a small rock cause piezoelectric discharge? Could triboluminescence appear in bits of quartz being knocked off by a rock? I do remember we would wait until it was getting dark to see the sparks well, but none of the possible effects would be seen well in bright daylight. ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [April 21, 2023, 2:53pm UTC](https://boards.straightdope.com/t/what-would-cause-a-coffee-cup-to-give-off-sparks-when-smashed/983004/19 "2023-04-21T14:53:13Z")
> [@LSLGuy](#): > > I’m not sure that at the margin encouraging highly frustrated people to learn to enjoy breaking stuff is all that good for the world. Or the safety of their roommates. Although when has that consideration ever stopped a profitable business idea? Or just be honest that people enjoy breaking stuff. It’s not venting or cathartic, it’s just fun. When I did a remodel, I greatly enjoyed taking a sledgehammer to one of my (non-loadbearing, I checked) walls. In the spring, I find it entertaining to break up the ice on my pond. When I did tree trimming and landscaping, I took great satisfaction in reducing a once towering giant to a pile of firewood and woodchips. Marketing it as a rage room implies that violence is a reasonable reaction to frustration, and that breaking things will reduce that frustration. Can’t adults just have fun? ---
**Author:** ![Babale](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/babale/32/15666_2.png) [@Babale](https://boards.straightdope.com/u/Babale)\ **Post date:** [April 21, 2023, 3:43pm UTC](https://boards.straightdope.com/t/what-would-cause-a-coffee-cup-to-give-off-sparks-when-smashed/983004/20 "2023-04-21T15:43:55Z")
> [@Smapti](#): > > For those unfamiliar with this relatively new business model Don’t they have one of those in 1940’s _Pinocchio_, on Pleasure Island? ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [April 21, 2023, 3:48pm UTC](https://boards.straightdope.com/t/what-would-cause-a-coffee-cup-to-give-off-sparks-when-smashed/983004/21 "2023-04-21T15:48:07Z")
> [@k9bfriender](#): > > Marketing it as a rage room implies that violence is a reasonable reaction to frustration, and that breaking things will reduce that frustration. Can’t adults just have fun? Sure they can have fun. They can have fun, as you rightly say, breaking things. I sure have over the years. Not so much recently, but much more for lack of opportunity than any sort of prudish holier-than-thou attitude about it. It’s the labeling “rage room”, and the scene setting of a standard living room or kitchen that I object to as psychologically unhealthy _at the margin_. In a society that is rapidly turning to nihilistic violence (or at least erotic fantasies of nihilistic violence) as the first resort answer to everything, “rage rooms” are just that much more grease on the skids. [Next page](https://boards.straightdope.com/t/what-would-cause-a-coffee-cup-to-give-off-sparks-when-smashed/983004.md?page=2)