Lumen, 19d. definition is 'preserver'. An unusual (usually longer) word for 'person raising sunken ship', minus one letter.
27d. definition is 'bowl'. 'cast', with misprint, + 'copper' + 'rounded mass' minus first and last letters.
I enjoyed this and partial thematic knowledge helped somewhat past a certain point in the solve. However, I came here to see if anyone else was briefly held up by a ‘wrong right answer’ in 19d that parses fine but generates a letter other than that which is required for the message to make sense. Such ambiguity exercised my eyebrow a little…!
yes robt - I was there initially - until it became obvious it was incorrect ... spelling out 'part of a line' etc ... which actually incorporates my initial mistake ....