Heating food in gravy on Shabbat

I understand that Ashkenazim can heat damp food (’Lach’) on shabbat up to the temperature of ’Yad Solelet Bo’. What are the precise parameters?: - what is the definition of damp food? Where is the border between damp food which can be heated and more liquidy food, which can’t. Examples would be appreciated - What is the temperature of ’Yad Solelet Bo’?

Shemirat Shabbat K'Hilchata writes that "Yad Soledet Bo" is more than 45 degrees Celsius (113 degrees Faranheit). Regarding your first question: its premises are incorrect. 1- On shabbat, it is forbidden to heat uncooked food (wet, damp or dry)even to a temperature that is less than Yad Soledet Bo; this if you are putting the food at a proximity to the source of heat where - if it were not removed in time - it could reach Yad Soledet Bo. 2 - Dry, cooked food (for example shnitzel that has already been cooked) can be heated on shabbat without fear of it being "recooked". Even so, it cannot be put on an open fire due to rabbinical prohibitions. There are differences of opinion as to how dry is dry. Shnitzel is dry even though it has some moisture; there are poskim who following Rabbeinu Yeruham, feel that a cooked food is seen as dry if it is mainly dry - for example rice with some gravy, stew which is mostly meat with some gravy etc. 3- There is also no problem of recooking hot cooked liquid food (hot soup) when you replace it on the plata. If the soup has cooled to less than Yad Soledet Bo,but is still warmer than room temperature, Ashkenazim permit it to be reheated and Sephardim do not. Again it cannot be replaced on an open fire. These halachot have many details and it is wise to learn them systematically within a study-framework, like a shiur.