Received a call from a local fire restoration contractor, that I know, this morning. I'd recently mentioned looking for sash weights and he said he'd keep on eye open. He informed that he had 11 free sash weights in his office for me if i still wanted them. I drove down to get them.
One look and I fully understood the reluctance of a couple of posters to try using this material. These poor weights look like swiss cheese afflicted with bed sores. LOTS of large voids and air pockets. I now know for sure that there are major differences in quality among them. I recently bought 12 weights from a fellow that were nice clean wonderfully solid pieces of CI. I scaled them back by about 3/16 diameter and the rest is good usable metal. These latest weights are likely to yield only small flats if they are even usable at all. Truthfully, they could just as easily wind up in the trash.
Moral of the story is don't offhandedly discount using old sash weights, but check them closely to make sure they are solid well made pieces before dragging them home. It doesn't take a genius to spot the difference.... trust me....LOL Just another fine example of several varied experiences producing diametric opinions.... and all of them correct.
Steve