Fill a 24 quart pot half full of water. Put on the stove. Boil the water on high heat. [NOTE - you can cover the pot with a lid to make the boiling process faster.]
Add the unthawed pork neck bones and pork feet bones. Wait for the water and bones to boil again.
Scoop out the scum and floating impurities from the pot until you don't see anymore floating to the surface. This may take anywhere between 20-40 minutes.
Strain the bones and clean the pot. Thoroughly rinse and wash each bone by hand. Put them back into the pot with fresh water and let it boil again.
Let the pot boil on high heat for at least 6 hours and up to 10 hours. You'll get a more viscous broth by boiling 8-10 hours. Do not cover the pot completely with a lid but you can leave a lid half covered. Add more water periodically as the water level decreases. Stir the bones every 15-25 minutes.
Use a refractometer to measure the "thickness" of the broth. The broth should measure at 4.5 or higher on the "BRIX" scale on the refractometer.
Using a fine strainer, strain all the solids and reserve the remaining liquid broth.
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