This question might be a bit weird, but I just asked myself why a wooden spoon creates bubbles when put in oil at about 170°C. My idea is, that the water in the spoon reacts with the Oil, but why does this just starts to happen when the Oil reaches approx 170°C? Why does this not happen at 100 or 120°C ?
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1$\begingroup$ Can you describe the spoon a little more? Is it old? Brand new? $\endgroup$– GertCommented Jan 28, 2021 at 14:25
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$\begingroup$ Well, it's just a regular spoon for cooking. This worked for old and new spoons as well $\endgroup$– PhicalcCommented Jan 28, 2021 at 15:14
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$\begingroup$ And you did actually compare behaviour at $100^{\circ}\mathrm{C}$ and $170^{\circ}\mathrm{C}$? $\endgroup$– GertCommented Jan 28, 2021 at 15:17
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1$\begingroup$ @Gert yeah, I did. Actually, this is a common trick to find out if Oil for frying has the right temperature. When it starts bubbling the temperature is pretty close to 170 °C $\endgroup$– PhicalcCommented Jan 28, 2021 at 17:20
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2$\begingroup$ @lee No, I think it's fine here. The process is likely to be a physical one, not a chemical one (so says my gut as a chemist) $\endgroup$– GertCommented Jan 28, 2021 at 17:51
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2 Answers
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Wooden spoons are porous, and have oil, water, and air embedded in their surfaces after being used for a while.
Putting a spoon like this into hot oil will boil the water in the surface, and expand any air there, thus creating bubbles of water vapor mixed with air.
If you then allow the oil and the spoon to cool off together, the remaining air in the (hot) spoon will contract and pull oil into the deep pores of the wood as it does. This will form a thick layer of oil-saturated wood on the spoon surface, and suppress bubble formation the next time you stick it into a container of hot oil.
answered Jan 28, 2021 at 18:12
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$\begingroup$ The OP said that he saw bubbles on both the old and new spoons as well. According to your answer this wouldn't happen because, there'll be a thick layer of oil-saturated good which suppress the formation of bubbles. Could you please explain this? $\endgroup$– leeCommented Jan 29, 2021 at 3:20
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$\begingroup$ @lee Don't you wash your cooking spoons? $\endgroup$ Commented Feb 14, 2022 at 23:22
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I doubt whether this has to do with the content of the spoon, as old and new spoons behave in the same way. I suspect the reason is that oil is a mixture of different oils, and that oils with smaller molecules have a lower boiling temperature. The oil may contain a small proportion with a boiling temp of about 170°C. The spoon has a rough surface on which bubbles are more likely to form. You could test this by seeing whether any other objects with a similar rough surface have the same effect.
answered Jan 29, 2021 at 7:49