How to make preserved eggs?

The method of making preserved eggs is as follows:

Egg 10 kg, water 10 kg, caustic soda 500-600g, black tea powder 200g and salt 400g.

First, we heated black tea powder with 3kg of water, boiled dark brown tea juice, and filtered the tea for later use. Then put caustic soda into a jar prepared in advance, add 7 kilograms of water and stir until it is completely dissolved, then pour in tea juice and salt and stir well again. After these jobs are done, put the eggs in, press them under the liquid surface, cover them and seal them, marinate them at 20℃ 13 days or so, and then take them out for inspection.

If the protein is transparent, take out the eggs and soak them in 50% feed liquid and 50% cold boiled water 10- 15 days. The concentration of feed liquid can be increased or decreased according to the solidification state of protein.