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Stoneware with rebar

Add tiny rebar to stoneware to dampen ringing
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Until recently I had some cheap plates that heated up more than the food in the microwave. Turns out that cheap ceramics are so porous that they absorb way too much water in the dishwasher.

So I got some cheap stoneware. Awesome. The only heat going into plates is now coming from the food itself when in the microwave.

However, there are two problems that come with stoneware - lack of friction and increased resonance - the first problem probably being a symptom of the second. Lets zoom into a piece of toast on a stoneware plate and explain what's going on :-

As the hard crumb texture traverses the plate, particularly any contours on the plate, this imparts a minuscule amount of energy to the plate and the plate starts oscillating (ringing like a bell). The surface wave on the plate now has a piece of toast riding on the tops of the waves which present much less friction to the toast. This can easily result in a butter-side down situation when the toast is carried out of the kitchen.

Clearly the solution is to add rebar to stoneware to deaden any resonant effect and turn that ring back into a clatter.

bigsleep, Dec 05 2018

Biscuit_20hammer [hippo, Dec 05 2018]

[link]






       You're right, earthenware is porous and can soak up water which will make it heat up dramatically in the microwave (and which is why earthenware flowerpots shatter or spall when left outside in freezing temperatures). Stoneware and porcelain tableware is fired at a higher temperature which makes it vitrified and non-porous. Your idea won't work though - rebar has a higher coefficient of expansion than the stoneware or porcelain plate and so will break the plate apart when it heats up. Also, while stoneware firing temperatures aren't higher than the melting point of steel, they're probably high enough to make it a bit soft and squidgy. Also, assuming the plates are fired in an electric kiln (i.e. in an oxidising atmosphere, rather than the reducing atmosphere of a gas kiln), the steel rebar will oxidise and probably produce rust-coloured iron oxide lines in the plates. A better approach would be to design the plate such that its resonant frequency is sufficiently different from the toast that you don't get the sympathetic resonance between the two which you describe.
hippo, Dec 05 2018
  

       It might be easier to put the rebar in the toast.
MaxwellBuchanan, Dec 05 2018
  

       Harmonically tuned toast
pocmloc, Dec 05 2018
  

       Tuning your toast to a specific frequency would also have the advantage that toast which had a resonant frequency outside the permitted range could be assumed to have poor structural integrity, with the concomitant risk of disintegration when laden down with butter and marmalade en route to your mouth and a resulting sticky patch on the floor of your breakfast room. A regime of toast frequency testing (e.g. see link) would avoid this.
hippo, Dec 05 2018
  

       Would jam not act as a damping material? It's certainly cheaper than rebar, and can be easily applied by any suitably experienced engineer by means of a trowel.
zen_tom, Dec 05 2018
  

       a trowel? - why not just use the mastic gun that the jam comes in from the shop?
hippo, Dec 05 2018
  

       I think hippo brings up a good point about the kiln temperatures, but there are a lot of steels. Inconel could handle middle of the road pottery firing temperatures of say 1300C. So you can make steel reinforced ceramic, but I worry that the microwave energy would concentrate on the steel, that would expand and then your plate would explode. Also, what are you doing putting toast in the microwave?
bs0u0155, Dec 05 2018
  

       // and then your plate would explode. //   

       HAHAHAHA ! AHAHAHAHAHAHA ! MUHWHAHAHAHAHAHAHAHAAA !   

       Ahem. <cough>.   

       Sorry, carry on.
8th of 7, Dec 05 2018
  

       What's the dielectric strength of stoneware? How much voltage develops on metals in a common microwave oven?   

       Putting rebar in your stoneware (or other ceramics) might also make them less likely to shatter on impact with e.g. the floor. There's a theory that I read, from either [wbeaty] or Richard Feynman, that when you drop a plate, it doesn't break on the first impact. Rather, it starts vibrating, and then when that part of the plate is swinging back toward the floor, it hits twice as fast as the first time, and that's what shatters it.
notexactly, Dec 06 2018
  

       It might - although you'd still have the problem of differing coefficients of expansion which would cause the plate to shatter when exposed to heat. You can strengthen pottery by adding larger particles (or 'grog') to the raw clay. These particles (of stone, sand, etc.) obstruct crack propagation and make the pottery stronger and more thermally resistant. Heavily grogged clays are used in raku where pottery is exposed to huge thermal shocks.
hippo, Dec 06 2018
  

       That's a better idea. But still, doesn't Inconel have a very low coefficient of thermal expansion, probably lower than the stoneware's?
notexactly, Dec 06 2018
  

       Not sure - it also might not be linear with temperature. Another issue is shrinkage - when you make something out of clay, depending on the type of clay, the piece will shrink by 10-15% during firing whereas the rebar won't.
hippo, Dec 06 2018
  

       Could resonance be prevented by incorporating a pseudo-random lattice of inhomogenous ceramic into the item at the time of creation ? The ceramics should shrink at a very similar rate during firing.
8th of 7, Dec 06 2018
  

       No, ceramic is already shrunk, and wouldn't shrink more being fired a second time. Another approach which might work is to use 'paper clay' - this is where you mix clay and paper pulp, make your plate or whatever out of this mixture and then fire it. All the paper burns out in the firing (first to ash, then the ash burns to CO2 and minerals), leaving a sort of loose honeycomb structure at the microscopic level.
hippo, Dec 06 2018
  

       Instead of rebar, perhaps a mixture of clay and steel wool could work. The fine fibres should be more tolerant of shrinkage and thermal expansion, but still add rigidity and prevent crack propagation - a sort of ceramic/steel pykrete.
mitxela, Dec 06 2018
  

       ^ [+]   

       // ceramic is already shrunk //   

       We weren't suggesting that the matrix was already fired, just that it was a different composition to make the object inhomogenous. The paper idea seems to fit the requirement quite well.
8th of 7, Dec 08 2018
  

       The thing is, it's highly unlikely that rebar will alleviate any resonance. It will be tightly enshrouded by the ceramic, and hence the whole thing will act as a single resonant unit.
MaxwellBuchanan, Dec 08 2018
  

       The microwave, obviously, would heat any metal rebar. Fortunately woven obsidian and carbon fiber rebar exists.
Voice, Dec 11 2018
  

       Rubber. Put a rubber ring on the bottom of the plates. Less skiddy. Less ringy. Dampening of enthusiastic vibrations. Cheap.
bungston, Dec 11 2018
  

       Why not just make rubber plates ?
8th of 7, Dec 11 2018
  

       Or rubber toast
pocmloc, Dec 11 2018
  

       // a rubber ring […] Dampening of enthusiastic vibrations //   

       Rubber rings and moist, enthusiastic vibrations…?
notexactly, Dec 12 2018
  

       Go on, back in your cage. Are you trying to get whipped again ?
8th of 7, Dec 12 2018
  
      
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