I have just finished some experiment at home using tea eggs.

  1. First I peel off the shell of the tea egg and place it in a bowl of white vinegar (of course, I consumed the rest of the egg). Not surprisingly, bubbles were seen as the carbonate in the eggshell reacted with the vinegar.
  2. After a day, part of the mixture was decanted into a small glass jar. Sodium carbonate (baking soda) chunks was then added which give off a lot of bubbles of $\ce{CO2}$ plus thick foam of undissolved eggshell mixture. This is repeated until no more reaction occurred (meaning the acid is completely neutralised with the baking soda in excess). After it is settled, a simple filter is made using tissue paper (Coles White Facial Tissue) as the mixture is then poured on top of the tissue into a clean glass cup. This is then left for 7 days, sealed by the tissue paper.
  3. More white vinegar is added to the same liquid level. This is then left to evaporate a bit (and part of the liquid is decanted into another glass jar. Step 3 is then repeated until all eggshell has dissolved (leaving behind brown film like residue which is the membrane of the egg and also the tea leaf related residues
  4. After that,the clear solution is transferred by capillary action using a rolled tissue paper (same brand) to a new glass jar. A few hours later, some white powder is formed on the rolled tissue paper. This white solid is then scrapped off to be stored in another glass jar.
  5. A few days later after realising the colorless solution in the glass jar still does not evaporate significantly, it is poured onto a spread out tissue placed on a clean flat surface. After the solution evaporated, similar white powder was deposited near the edge of the tissue. This is then scrapped off to the same glass jar that contain the white powder.

Now when I prepared to wash everything, I noticed some strange slimy looking sediment (which look like tangled threads and web like in solution) formed that was not there 7 days ago.enter image description here

I have a couple of suspicions:

  • Dissolved egg proteins that precipitated
  • Some unknown reaction between sodium carbonate and eggshell solution
  • A biofilm of some unknown microbes

Any idea what that white stuff could possibly be?

  • $\begingroup$ The white powder is likely either sodium or calcium acetate, likely a mixture of the two. Egg shells are mainly calcium carbonate and baking soda is sodium bicarbonate, which each react with the acetic acid (vinegar) to form acetates releasing carbon dioxide bubbles. As far as the the slimy stuff goes, your protein guess seems pretty plausible. $\endgroup$ – ChemBird Feb 11 '17 at 8:07
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    $\begingroup$ Possible duplicate of Why do the physical properties of an egg shell change when the egg shell is exposed to vinegar for a week? $\endgroup$ – Mithoron Feb 11 '17 at 23:54
  • $\begingroup$ Hmmm... I am not sure if the suggested link resolves it fully, given how I actually kinda separated the egg membrane from the eggshell itself by the filtration, unless part of the protein dissolved in the baking soda and then deposited afterwards after standing for a week $\endgroup$ – Secret Feb 12 '17 at 6:55

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