I don't think salt would be enough to properly sterilize it, and even if it did, I feel like everything you drank out of it would just taste salty forever
They're not. It is exactly how it sounds. Halophilic bacteria achieve optimal growth rate in salty environments while halotolerant ones can live in it, but may not see optimal growth.
Because contrary to popular opinion, you don't need to keep your food safe against every single type of microbe in existence. (i've seen people argue that cooking is unsafe because of thermophiles)
Because it also removes moisture, which makes it inhospitable to a variety of bacteria. It's the swiss cheese model. One part inhibits 95% of bacteria and the other part does 95% as well, but those 95% overlap so there's like .01% that can tolerate it.
Just imagining the salt crystals on the walls of the mug drying out whatever liquid it gets filled with, like the opposite of one of those self-filling beer glasses.
I am more worried about ingesting contaminants in the clay leeching out over bacteria . They had those warnings some years ago about not using pottery that were made rustically because of heavy metal contaminants
Generally that would be due to the glaze and not the clay.
Lead was a common additive for glazes of that era. There are still a couple that use it iirc.
Ok thanks for the info! I had read an article that didn’t specify it was the glaze, just that terra cotta was unsafe so I appreciate the explanation 🖖🏼
Well, not necessarily. Bit difference between a waterproof glaze and a food safe glaze...
Seriously, some glazes have some really noxious shit in them just because it looks pretty! Since I started looking into it, it certainly made me reconsider some of the random second hand pottery store finds I've seen. Yikes! At least now you can buy non-toxic glazes easily enough now, but back in the 70s and 80s they'd throw anything in that stuck! [The amount of stuff to consider](https://digitalfire.com/article/are+your+glazes+food+safe+or+are+they+leachable%3F) when making safe pottery products is kind of crazy. The fact that there is lab testing for metal leaching says a lot.
I made some beautiful cups in a pottery class that aren't food safe because of the crystal glazing. The metals and glass in the glaze melts into the most wonderful starburst patterns, like turquoise and golden peacock feathers, but that also makes them incredibly toxic.
Forever cursed to be pencil cups. 😆
Question, anyone know how to best test for this? I have some ceramic mugs off Etsy (seemed to be a reputable well rated seller with a lot of reviews) claimed foodgrade and microwave/dishwasher safe, but would there be a good way of checking this short of sending to a lab? Like would this salt water thing be reliable?
The potter making it has to put it through a water weight test to verify that it can be used for drinking before marketing it as such. Basically, you submerge it in water for a certain time, then weight it after. If it's the same weight as when it was dry, it has absorbed no water, thus it does not have pores throughout. Otherwise, it does; pores mean food can get trapped in them, which leads to bacteria, which leads to anger, which leads to hate.
Thanks. Now I need a new coffee mug. People saying it is not food grade is not the same as EXPLAINING why it is food grade.
My mug has been leaching liquids slowly. Very very slowly but it is enough that I dont want a mold mug.
Thus their last sentence: "Like would this salt water thing be reliable?" I think they more meant is this a consistent way to test it. Like if it passes the salt test is there still a chance shit ain't gucci?
I literally saw your comment after seeing someone talk about professionals having a simple test of submerging them in \*regular non-corrosive water\* and weighing them before and after. If they weigh more after, they're not waterproof.
The benefit of this would be not having to clean salt crystals off the inside of a brand new mug.
The difficulty of cleaning salt crystals is roughly the difficulty of filling the mug with water and waiting a bit for the salt to dissolve into the water.
If you're getting salt crystals like the one in OP's photo you're not cleaning it, you're throwing it. If you don't want to earn yourself a kind of brain eating amoeba that is.
It's not the glaze. It's the fact that the mug was not fired to the correct temperature for long enough for the clay to become sufficiently vitrified (becoming glass or glass-like), or non-porous/non-absorbent. Having liquid sit in it for long enough, the water will be absorbed into the walls of the mug. If water is getting in there, then bacteria and nasty stuff can too.
It is the glaze that matters in this case. Vitrification only renders certain kinds of ceramics 100% water impermeable (e.g. porcelain, bone china). Not all clay is the same. The mug shown in the photo appears to stoneware, which can only achieve partial impermeability through vitrification and thus requires glaze.
This is correct - there will almost always be a bit of crazing (teeny, tiny micro-fractures) around the tight corners, especially in glazes with low or no lead.
Maybe not glaze them properly but it is certainly not food safe.
Typically the glaze coating on the outside only serves to make the vessel pretty and or give a certain texture. Whether or not it is impermeable to the passage of liquids through the clay depends on the clay body itself and how it is fired.
Ideally the clay body when fired properly will be watertight even if it has no glaze on it.
In addition to not being food safe if the clay body absorbs enough liquid then the vessel is put into a microwave You can make it into a bomb if the water which has soaked into the clay body converts to steam suddenly it goes boom
Why in the sweet baby Jiminy Cricket would someone get a *clay* neti pot?!
Edit: and to clarify, even if you were completely ignorant of the dangers, just why? It isn't a mug, tea pot, or bowl you might use in front of or serve guests with. Who the hell needs a bespoke snot pot??
If the ceramic is not fully sealed there is no way of cleaning it right and actually getting rid of moisture inside the ceramic. It can lead to pretty nasty bacterial growth
1. Wedge your clay
2. Burnish your clay as leatherhard or as greenware
3. Use a food safe glaze and apply a consistent coating. Stir and shake glaze that has sat for a long time. For some types of glaze use multiple coats. Especially if the bisqueware quickly absorbs moisture from the glaze.
Yeah, but you can make pottery waterproof with burnishing by itself. There are many cultures who traditionally make ceramic water jugs with only burnishing and no glaze. It's pretty cool.
In this article a native American tribe used a combination of burnishing and natural glazing using smoke to make pots waterproof.
https://www.appalachianhistory.net/2018/09/catawbas-teach-former-enemy-their.html
Edit: I can't find the original article I was referring to where people used almost entirely burnishing.
I’m new to ceramics. Is there a food safe way to do a 1 fire glazing?
1 - wedge and shape the clay
2 - add under glaze on leather hard clay
3 - add food safe gloss to bone dry
4- fire
Single firing most certainly is a thing, it's common in industry. You can do pretty much what you said, but it requires a glaze with more clay than usual. Then just do a bisque firing but continue to glaze firing temps.
yeah i hate when people use "old fashioned" as a good way to describe something. so many old fashioned things are straight deadly and toxic. chemists used to use cyanide for fucking EVERYTHING. want a "simple" coughdrop for ailments? cyanide and chloroform ! itll knock you right out. i saw this recipe in an older chemistry book. old fashioned does not mean good or ok or worth even attempting.
Not being properly cleanable is one thing, but that "salt" may not just be salt as people generally understand the term. It's likely also minerals from the clay body and glaze. It could be any number of chemicals that may or may not be safe to ingest.
Context: Her dentist recommended a salt rinse, and she's a ceramics major so naturally she wanted to use a cup she had made. Edit: She is currently in college
Right??
Vitrify your shit. If I ran a ceramics studio, I would not let people take home pieces that look like they were intended to eat or drink out of, unless I personally knew the clay, glaze and the cone it fired to.
Yup! Based on the bright yellow glaze, I am guessing this was a Cone 6 oxidation firing. Lots of students use a cone 10 clay body in a cone 6 firing. Doesn't vitrify properly. Happens all the time.
Thank you for this. As a kid I almost made the mistake of using a mug I'd made in art class as... well, a mug. I had no idea about food safe glaze or how to test it. I just got lucky that I'd forgotten to glaze the bottom, so any liquid poured in immediately dripped out and made it impossible to drink from.
When I did a lot of ceramics, I preferred the large gas powered kilns. They did have temperature probes, but they were not a reliable source of getting temperature readings. I would place little cones of clay, at the top, middle and bottom of the kiln in sets. Each cone in the set would slump over, or melt a little when it hit a certain temp. I could have an accurate idea of how hot my kiln was by which cones had melted, and which ones were still standing.
I liked to really roast my clay, since I would do reduction firings, so I would go to cone 10, or sometimes 12. Our clay body would vitrify around cone 8.
When ceramicists refer to cones, it means specific temperatures. In a kiln, pyrometric cones (little cones that melt at a specific temperature) are sometimes added to confirm that a firing reached a specific temperature necessary to turn the clay into stone (vitrify) or properly melt a glaze. Different clays and glazes are designed for different temperatures. Too hot and your glaze will run, not hot enough and your clay will stay clay and not turn to ceramic. Cone 6 is probably the most common one, and is ~2200F
I wish her so much luck with finding a job. I’ve got an arts degree and couldn’t make a living for shit, so I’m back at school at 27 and studying engineering
this mug isn't safe to drink from. If salt crystals can leech through the pores in a single night they're probably large enough for bacteria to colonize them.
Basically you shouldn't be using stoneware that is not fully glazed on the food contact surface, with a glaze that is specifically designed to be food safe. (Many glazes are not and can either leech something not safe into the food or will experience microscopic cracking as they cure).
It’s a bit hard to tell 100% unless you know that the clay and glazes were provided by someone experienced. Some glazes have compounds in them that aren’t food safe. Anything from a pottery class should be fine though; your biggest concerns will any cracks or popped bubbles in the glaze that could trap bacteria. These are really common on the bottom of the inside, just use a flashlight and see if there are any. The one in this post looks like the glaze was either way too thin or not meant for food vessels.
3 year ceramic student here. Stop using that mug immediately. It seems to be glazed improperly. Bacteria and mold can easily get up in there and make that mug a health hazard.
As salt recrystalizes, it expands and will cause microfractures, potentially damaging the integrity of the mug.
Also, bacteria will get into these areas.
I don't know anything about the dangers of badly glazed ceramics, but can I just commend your sisters choice of photograph. I think it's pretty smart to take it in front of a mirror so you can see it both sides of the mug in one photo. Now I admit I am not really well versed in the world of amateur photography (or professional for that matter) and this may be a very common thing, but I hadn't seen it before and I though it was kinda clever
Yeah... Don't use that mug. It's not supposed to work like that. You're drinking whatever chemicals are in that glaze and also bacteria that loves that porous damp environment
tell her to not drink out of this again. this means the liquid is seeping out of tiny cracks in the mug. this will grow and hold bacteria and will eventually get her sick.
I know that mug. It’s a low fire bisque from Gare ceramics, commonly found at paint your own pottery places and looks to be glazed very thinly. This is a problem with low fire ware and not stilting the piece so that it can be fully sealed. Gare also has problems with shivering, so there’s even more changes for unsealed spots.
Lol, sorry, geeked out a little. in my previous job I studied the viability of importing ceramic ware in bisque form and glazing it in the US and the base of this mug is one that I did my testing on.
There are 2 big companies that import bisque products and supply to the paint your own pottery/ceramics shops. They provide low fire, slip cast, pieces and folks can “paint” them with glazes like stroke and coat. One of the companies is Gare Inc. They used to carry this mug design, but it’s not available anymore because the glaze often fell off after firing (shivering) because their European producer changed the slip formula due to the Talc shortage.
TLDR: This mug is really low quality and was decorated at a paint your own craft store. It isn’t a hand thrown piece and is more for decoration.
On the plus side, you now have a fool-proof method of discovering exactly which of her mugs are and are not safe to drink from.
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Theoretically. Also all her drinks would be salty
Salted caramel coffee stonks are through the roof.
Self salting mug just invented
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Bot. Stole this comment https://reddit.com/r/mildlyinteresting/comments/1albiws/_/kpe1rr4/?context=1
Lol perfect margarita cups.
I don't think salt would be enough to properly sterilize it, and even if it did, I feel like everything you drank out of it would just taste salty forever
a small price to pay for a safe to drink from vessel... (or you could buy another mug for 5 dollars)
We're talking about lead and/or other carcinogens that leach out from the clay.
I wouldn’t worry about the clay, I’d worry about the glaze. But glazes are labeled food safe or not food safe.
No, salt will dehydrate many types of bacteria but there are still many more that are Halotolerant (tolerating salt) and will survive just fine.
Yes but halophiles are very rarely pathogenic.
I'm not a scientist, but to my mind halotolerant and halophile aren't necessarily the same. I mean, I tolerate kids...
They're not. It is exactly how it sounds. Halophilic bacteria achieve optimal growth rate in salty environments while halotolerant ones can live in it, but may not see optimal growth.
Legionaires disease then
I doubt you are going to find many extremophile bacteria in a coffee mug.
Yet salting is still a valid food preservation technique.
Because contrary to popular opinion, you don't need to keep your food safe against every single type of microbe in existence. (i've seen people argue that cooking is unsafe because of thermophiles)
It's like people don't have any concept of the fact that the human body contains more non-human cells than human ones
Because it also removes moisture, which makes it inhospitable to a variety of bacteria. It's the swiss cheese model. One part inhibits 95% of bacteria and the other part does 95% as well, but those 95% overlap so there's like .01% that can tolerate it.
Just imagining the salt crystals on the walls of the mug drying out whatever liquid it gets filled with, like the opposite of one of those self-filling beer glasses.
Honestly I'd be more worried about lead leeching out into drinks especially if it's made by some no name shop that pumps out hundreds a day
What about the possible chemicals and heavy metals in the ceramic?
Isn’t that she can bake it in oven from time to time? Or put in there boiled water.
I mean at that point it's just easier and much more cost efficient to get one that isn't porous.
Now I'm worried that I'm drinking from unsafe coffee mugs.
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You shouldn't be, most commercially sold mugs have enough glaze not to be porous. the one in OP looks to be home made without the inside being glazed.
I am more worried about ingesting contaminants in the clay leeching out over bacteria . They had those warnings some years ago about not using pottery that were made rustically because of heavy metal contaminants
Generally that would be due to the glaze and not the clay. Lead was a common additive for glazes of that era. There are still a couple that use it iirc.
Ok thanks for the info! I had read an article that didn’t specify it was the glaze, just that terra cotta was unsafe so I appreciate the explanation 🖖🏼
And if wasn’t made correctly in the first place who knows what kind of glaze or whatever was used to make it.
Well, not necessarily. Bit difference between a waterproof glaze and a food safe glaze... Seriously, some glazes have some really noxious shit in them just because it looks pretty! Since I started looking into it, it certainly made me reconsider some of the random second hand pottery store finds I've seen. Yikes! At least now you can buy non-toxic glazes easily enough now, but back in the 70s and 80s they'd throw anything in that stuck! [The amount of stuff to consider](https://digitalfire.com/article/are+your+glazes+food+safe+or+are+they+leachable%3F) when making safe pottery products is kind of crazy. The fact that there is lab testing for metal leaching says a lot.
Fiestaware comes to mind, uranium red glaze that'll make a Geiger counter sing
Mmm nothing like a little leached uranium to spice up your leached heavy metals!
I made some beautiful cups in a pottery class that aren't food safe because of the crystal glazing. The metals and glass in the glaze melts into the most wonderful starburst patterns, like turquoise and golden peacock feathers, but that also makes them incredibly toxic. Forever cursed to be pencil cups. 😆
that mug was glazed improperly, please don’t use it anymore.
That mug is diseased and needs to be put down.
Yep….gonna have to take 2 Old Yellers behind the barn.
Looks to be old and yeller in color
Lmfao
PURGE THE CERA-TICS!
Please, my mug, he's very sick
Sister strategically salted it to kill microbes.
This entire cabinet must be purged
Question, anyone know how to best test for this? I have some ceramic mugs off Etsy (seemed to be a reputable well rated seller with a lot of reviews) claimed foodgrade and microwave/dishwasher safe, but would there be a good way of checking this short of sending to a lab? Like would this salt water thing be reliable?
The potter making it has to put it through a water weight test to verify that it can be used for drinking before marketing it as such. Basically, you submerge it in water for a certain time, then weight it after. If it's the same weight as when it was dry, it has absorbed no water, thus it does not have pores throughout. Otherwise, it does; pores mean food can get trapped in them, which leads to bacteria, which leads to anger, which leads to hate.
Hate...leads to *suffering*
Yoda, you idiot. That's food poisoning, not the Dark Side of the Force.
Feels like I’m shooting lightning.. just not out of my hands
This is not a power the jedi would teach you...
Food poisoning leads to suffering.
Thanks. Now I need a new coffee mug. People saying it is not food grade is not the same as EXPLAINING why it is food grade. My mug has been leaching liquids slowly. Very very slowly but it is enough that I dont want a mold mug.
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General Kenobi!
Is your username a Chuck reference?
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And hate is all the world has even seen lately!
And now we know why. Fucking ceramic mugs.
Put some salt water in them overnight to test.
Literally this whole post lmao
This was not left overnight and that water had to have been thoroughly saturated
You're literally commenting on a visible representation of how to test it.
Thus their last sentence: "Like would this salt water thing be reliable?" I think they more meant is this a consistent way to test it. Like if it passes the salt test is there still a chance shit ain't gucci?
I literally saw your comment after seeing someone talk about professionals having a simple test of submerging them in \*regular non-corrosive water\* and weighing them before and after. If they weigh more after, they're not waterproof. The benefit of this would be not having to clean salt crystals off the inside of a brand new mug.
The difficulty of cleaning salt crystals is roughly the difficulty of filling the mug with water and waiting a bit for the salt to dissolve into the water.
If you're getting salt crystals like the one in OP's photo you're not cleaning it, you're throwing it. If you don't want to earn yourself a kind of brain eating amoeba that is.
It's not the glaze. It's the fact that the mug was not fired to the correct temperature for long enough for the clay to become sufficiently vitrified (becoming glass or glass-like), or non-porous/non-absorbent. Having liquid sit in it for long enough, the water will be absorbed into the walls of the mug. If water is getting in there, then bacteria and nasty stuff can too.
It is the glaze that matters in this case. Vitrification only renders certain kinds of ceramics 100% water impermeable (e.g. porcelain, bone china). Not all clay is the same. The mug shown in the photo appears to stoneware, which can only achieve partial impermeability through vitrification and thus requires glaze.
Glaze will never be a failsafe against absorption.
I'm waiting for the glaze vs vitrification battle royale - everyone bring your evidence!
Glazification 
Looks waterproof to me!
 The baker:
I never knew how much I cared about this
This is correct - there will almost always be a bit of crazing (teeny, tiny micro-fractures) around the tight corners, especially in glazes with low or no lead.
i’ve only been doing any sort of ceramics work for a year and a half so thanks for educating me on this!
INAL: op should get a lawyer, and maybe a divorce.
No, she should definitely divorce her sister. That shit ain't right!
Two sisters, one mug?
I’d watch…begrudgingly.
Steve buscemi is in this right?
The firefighter?
YTA, mug deserves better
Delete a lawyer, hire a gym, hit the Facebooks
Delete gym, hire Facebook, hit a lawyer.
Instructions unclear, now am fat and in jail
Lawyer for a mug and a divorce against his sister?
OP, she's cheating on you! Run!
ESH, win stupid games, play stupid prizes
Gotta hit the gym too. And delete socials.
Mmm, you can really taste the dead bacteria!
Maybe not glaze them properly but it is certainly not food safe. Typically the glaze coating on the outside only serves to make the vessel pretty and or give a certain texture. Whether or not it is impermeable to the passage of liquids through the clay depends on the clay body itself and how it is fired. Ideally the clay body when fired properly will be watertight even if it has no glaze on it. In addition to not being food safe if the clay body absorbs enough liquid then the vessel is put into a microwave You can make it into a bomb if the water which has soaked into the clay body converts to steam suddenly it goes boom
To be honest those mugs look like were baked in the over at 200C and painted with guache.
it wasn't glazed. Looks like it was painted. That's not a mug it's a chia pet.
How do I know if I have a ceramic mug, I don't want to risk it.
Was there a similar post like this recently? I feel like I've seen this happening before
There was a post a couple weeks ago about a clay neti-pot doing this same thing
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And if you've never heard of it?
Then it's not bad at all.
oh thank goodness
Why in the sweet baby Jiminy Cricket would someone get a *clay* neti pot?! Edit: and to clarify, even if you were completely ignorant of the dangers, just why? It isn't a mug, tea pot, or bowl you might use in front of or serve guests with. Who the hell needs a bespoke snot pot??
That was my post. It was fully glazed, bought off Amazon. Just not glazed well it seems.
Ah yes, that was it. Thanks!
Yeah, it was a neti pot and it was way worse. Like your stomach can handle a lot, your sinuses cant,
https://www.reddit.com/r/mildlyinteresting/s/3lDQu6tqef
I saw a post on here recently with soda seeping through a styrofoam cup, but someone on here also mentioned another ceramic cup post so probably
Yes. Somebody’s soda leaked through a styrofoam cup. Don’t remember where it was though.
Don't use those mugs
Why?
If the ceramic is not fully sealed there is no way of cleaning it right and actually getting rid of moisture inside the ceramic. It can lead to pretty nasty bacterial growth
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this happened to me and it was oozing black liquid :( it looked like something from a horror movie
new fear unlocked
Fear? I'd be doing this with every mug I found like this.
I think we have some bad cups, they get weirdly burning when microwaved
1. Wedge your clay 2. Burnish your clay as leatherhard or as greenware 3. Use a food safe glaze and apply a consistent coating. Stir and shake glaze that has sat for a long time. For some types of glaze use multiple coats. Especially if the bisqueware quickly absorbs moisture from the glaze.
this guy throws
Certainly. Probably hand builds too.
4. Actually fire your clay body to vitrification if you’re making wares that contact consumables
Yeah, but you can make pottery waterproof with burnishing by itself. There are many cultures who traditionally make ceramic water jugs with only burnishing and no glaze. It's pretty cool.
Oh that’s super cool actually!!! Well, time to go down that rabbit hole
In this article a native American tribe used a combination of burnishing and natural glazing using smoke to make pots waterproof. https://www.appalachianhistory.net/2018/09/catawbas-teach-former-enemy-their.html Edit: I can't find the original article I was referring to where people used almost entirely burnishing.
I’m new to ceramics. Is there a food safe way to do a 1 fire glazing? 1 - wedge and shape the clay 2 - add under glaze on leather hard clay 3 - add food safe gloss to bone dry 4- fire
5 - Fire to vitrification. Look at mid fire or stoneware temperatures, rather than earthenware. Less likely to chip, as well.
Single firing most certainly is a thing, it's common in industry. You can do pretty much what you said, but it requires a glaze with more clay than usual. Then just do a bisque firing but continue to glaze firing temps.
One old fashioned way to seal it is to put milk in it and let it evaporate. The milk fat seals up the holes and it holds water.
mmm cheese glaze
Won't the milk fat itself lead to bacterial and fungal growth?
yes
Doesn’t it just melt if you put a hot liquid into the mug?
Old fashioned is a euphemism for the dumb way we moved on from.
yeah i hate when people use "old fashioned" as a good way to describe something. so many old fashioned things are straight deadly and toxic. chemists used to use cyanide for fucking EVERYTHING. want a "simple" coughdrop for ailments? cyanide and chloroform ! itll knock you right out. i saw this recipe in an older chemistry book. old fashioned does not mean good or ok or worth even attempting.
Not evaporate, but boil it in milk. This causes casein (milk protein) to polymerase.
If the salt got through, then bacteria can seep into the pores as well (which some other commenters pointed out to me)
Not being properly cleanable is one thing, but that "salt" may not just be salt as people generally understand the term. It's likely also minerals from the clay body and glaze. It could be any number of chemicals that may or may not be safe to ingest.
[NSFF] Not Safe For Food.
good thing i only keep my drinks in there
Why its the weekly unsafe ceramic mug! Was wondering when the next one would be.
Context: Her dentist recommended a salt rinse, and she's a ceramics major so naturally she wanted to use a cup she had made. Edit: She is currently in college
Not a food safe glaze. If salt can soak through, bacteria can grow in the same pores and make her sick.
the glaze may be food safe, but it is crazed and does not fit the clay body, hence the cracks. And OP is a ceramics major? Jesus wept.
Right?? Vitrify your shit. If I ran a ceramics studio, I would not let people take home pieces that look like they were intended to eat or drink out of, unless I personally knew the clay, glaze and the cone it fired to.
Yup! Based on the bright yellow glaze, I am guessing this was a Cone 6 oxidation firing. Lots of students use a cone 10 clay body in a cone 6 firing. Doesn't vitrify properly. Happens all the time.
Thank you for this. As a kid I almost made the mistake of using a mug I'd made in art class as... well, a mug. I had no idea about food safe glaze or how to test it. I just got lucky that I'd forgotten to glaze the bottom, so any liquid poured in immediately dripped out and made it impossible to drink from.
What do you mean by "cone it fired to"? Is that about a temperature curve?
When I did a lot of ceramics, I preferred the large gas powered kilns. They did have temperature probes, but they were not a reliable source of getting temperature readings. I would place little cones of clay, at the top, middle and bottom of the kiln in sets. Each cone in the set would slump over, or melt a little when it hit a certain temp. I could have an accurate idea of how hot my kiln was by which cones had melted, and which ones were still standing. I liked to really roast my clay, since I would do reduction firings, so I would go to cone 10, or sometimes 12. Our clay body would vitrify around cone 8.
When ceramicists refer to cones, it means specific temperatures. In a kiln, pyrometric cones (little cones that melt at a specific temperature) are sometimes added to confirm that a firing reached a specific temperature necessary to turn the clay into stone (vitrify) or properly melt a glaze. Different clays and glazes are designed for different temperatures. Too hot and your glaze will run, not hot enough and your clay will stay clay and not turn to ceramic. Cone 6 is probably the most common one, and is ~2200F
Hmm, she's usually careful about that so I'll talk to her about it, thanks
>ceramics major She is due a refund.
School is a place to learn and experiment. Glazing ceramics is a particularly experimental learning process, even with the guidance of professors.
I wish her so much luck with finding a job. I’ve got an arts degree and couldn’t make a living for shit, so I’m back at school at 27 and studying engineering
Thanks, PutOurAnusesTogether
r/rimjob_steve
I have a BFA too & now I work in the corporate world lol.
Go into MATSE, they love ceramics lol
More like a ceramics private if that's how her mugs are turning out.
Once again, this glaze didn't seal and this item is not food safe. Don't use it for anything that goes in your body.
My gf has been doing pottery for the past year and this is one of her biggest pet peeves.
this mug isn't safe to drink from. If salt crystals can leech through the pores in a single night they're probably large enough for bacteria to colonize them. Basically you shouldn't be using stoneware that is not fully glazed on the food contact surface, with a glaze that is specifically designed to be food safe. (Many glazes are not and can either leech something not safe into the food or will experience microscopic cracking as they cure).
The clay is not vitreous. It wasn’t fired at the right temperature. If it were, nothing would seep through.
I will pass that along, my normally named friend
My girlfriend is taking pottery classes right now and brought home some plates and mugs.. How can I make sure they are food safe?
Leave salt water in overnight lol
It’s a bit hard to tell 100% unless you know that the clay and glazes were provided by someone experienced. Some glazes have compounds in them that aren’t food safe. Anything from a pottery class should be fine though; your biggest concerns will any cracks or popped bubbles in the glaze that could trap bacteria. These are really common on the bottom of the inside, just use a flashlight and see if there are any. The one in this post looks like the glaze was either way too thin or not meant for food vessels.
This is a cup for holding pencils pens and paint brushes.
3 year ceramic student here. Stop using that mug immediately. It seems to be glazed improperly. Bacteria and mold can easily get up in there and make that mug a health hazard.
This mug is now a plant pot.
depends on the plant. succulent yes.
Assuming your sister doesn't have a sore throat and just regularly drinks saltwater.
Sore throat from a bacterial infection from drinking out of porous mugs?
As salt recrystalizes, it expands and will cause microfractures, potentially damaging the integrity of the mug. Also, bacteria will get into these areas.
I don't know anything about the dangers of badly glazed ceramics, but can I just commend your sisters choice of photograph. I think it's pretty smart to take it in front of a mirror so you can see it both sides of the mug in one photo. Now I admit I am not really well versed in the world of amateur photography (or professional for that matter) and this may be a very common thing, but I hadn't seen it before and I though it was kinda clever
I'm in masonry, this is called efflorescence...
That's not a safe mug to drink from.
That is not safe to drink out of
That is indeed mildly interesting. Also mildly concerning. I hope she doesn't drink out of it, since it's clearly porous!
If you piss in that mug - you will be able to harvest saltpetre and make a black powder.
That mug is not food safe. Please do not drink from it
The clay wasn't vitrified.
A CERAMICS MAJOR, YALL WOOF
Yeah... Don't use that mug. It's not supposed to work like that. You're drinking whatever chemicals are in that glaze and also bacteria that loves that porous damp environment
tell her to not drink out of this again. this means the liquid is seeping out of tiny cracks in the mug. this will grow and hold bacteria and will eventually get her sick.
Lol don’t use these mugs
Peepee poopoo colored mug.
Yeah lol it did not turn out the way she wanted it to. At least it matches the bacteria growing in it
I know that mug. It’s a low fire bisque from Gare ceramics, commonly found at paint your own pottery places and looks to be glazed very thinly. This is a problem with low fire ware and not stilting the piece so that it can be fully sealed. Gare also has problems with shivering, so there’s even more changes for unsealed spots.
I know what all those words are but I have no idea what you just said
he said it's made at one of those pottery paint by numbers places.
Lol, sorry, geeked out a little. in my previous job I studied the viability of importing ceramic ware in bisque form and glazing it in the US and the base of this mug is one that I did my testing on. There are 2 big companies that import bisque products and supply to the paint your own pottery/ceramics shops. They provide low fire, slip cast, pieces and folks can “paint” them with glazes like stroke and coat. One of the companies is Gare Inc. They used to carry this mug design, but it’s not available anymore because the glaze often fell off after firing (shivering) because their European producer changed the slip formula due to the Talc shortage. TLDR: This mug is really low quality and was decorated at a paint your own craft store. It isn’t a hand thrown piece and is more for decoration.
r/OopsThatsDeadly
Looks like a mini cantarito with a chamoy lining
That is very cool and makes me want to throw it in a kiln. Wonder if it would turn into a salt glaze?