Hello, I have recently been using petrobond to produce a clean face on castings. The problem is that I am using the petrobond to pack flasks out not just facing around the pattern. This seems to be consuming a lot of product in that when I have removed the casting, I am trying to seperate the burned sand from the clean un order to reuse said clean. In short, I am segregating the clean from burned. This method reduces the amount of clean sand quite a lot. I have a couple of questions that maybe forum members could offer guidance on. Question 1 - is it acceptable to use the petrobond to face around the pattern only then use say greensand to pack the remaining space within the flask? Question 2 - what methods are there to reprocess / relife the burned petrobond to allow a satisfactory reuse? Thanks in advance.
Lately most of my castings have been flat back plaques. I cast details in the drag along with the runner. Drag is petrobond, cope is greensand rammed separately. I dust the cope generously, assemble, and pour. When I separate the mold after casting, I have the flask sitting on its side and pull the mold halves apart slowly. The casting stays with the cope because of the sprue. Any petrobond that is burned to dust (within reason) just gets swept into the greensand heap, the rest gets mulled back into the petrobond supply. NO greensand in the petrobond though. Yes, the PB supply will get black in short order. There’s no avoiding that. Actually, to me anyway, fresh orange PB is undesirable. Periodically I mix a couple of lbs of brand new petrobond with black petrobond 50/50 in the muller to use as facing sand. When casting bronze, I know for sure that facing sand will be sacrificed. Bronze temps burn the shit out of it. Facing with PB and backing with greensand can be done but it’s dicey. Your PB can easily delaminate from the greensand for one, and you can end up contaminating your greensand heap with oily sand. You can recondition your petrobond, but you need direction from someone besides me. Others will speak up. The reusability of our sand is great feature for us but, like crucibles, etc, it is a consumable. Pete
I just make whole molds out of petrobond and put ALL the sand in the muller after to refresh it with a squirt or 3 of SAE 30W non detergent motor oil and a spritz or 2 of methyl hydrate to each half a 5 gallon bucket load. The only time I dispose of any is if it burns beyond black and turns grey, which only seems to happen to me with heavier section bronze castings. For a while I was making petrobond ingot molds too and that was pretty brutal for burning out the binder whenever I'd pour copper alloys. Never again! Jeff
