I had heard that many times and I bought a couple pallets of the pellets maybe 25 years ago or better and poured them into sealable plastic drums and just ration them as needed or when one of the heating elements go bad and ive got to drain some to replace. Not even sure what the pellets are but I treat them with care and a good mask. The thick bags of multi layer paper like simply said "Caustic Soda Pellets" nothing more. Since mine is more or less for personal use/friend use I mostly just add water and pellets when needed. It is killer for cast and steel but if I forget to pull a bearing or miss an aluminum part it eats them.
Ive given up on any local machine shops block/head cleaning as its substandard and then if they have to do it twice $100 to clean a block thats not really clean.... naa. Ive an old diesel fuel powered steam cleaner/blaster that does a better job. Its probably 50 years old and is not in the favor of the epa either.
Just find someone with a good caustic soda hot tank. Mine is 4x8 and ive dipped housings and they come out near like a new part in three days. Probably be easier and cheaper then your time and gallons of evap.
That's hard to find in the northeast thanks to the EPA, there used to be a place with a big dip tank ... can't remember it nationwide chain ... that I had the frame to my 56 chevy dipped in back in the 80's
