Just tried my first casting. I made my own greensand using a really fine decorative sand for houseplants and bentonite clay. The sand is like something you'd put in one of those desktop zen gardens. I made an open top mold and poured directly into the mold cavity. The water in the sand boiled up through the metal and I got aluminum swiss cheese. So my guess is too much water although the pattern came out cleanly. I could never get the sand to clump and break like it does in the videos I've watched. I added water and clay to get that clumping which obviously didn't work. Any advice would be appreciated.
Hi Allen- Do you know about what % or parts each you have in sand, clay, and water? Is you bentonite Western or Southern? sourced specifically for foundry or from another hobby/industry? The good thing is that you can leave the sand out to dry if it is too moist. Did you have enough left over to make an ingot? How did that look (if you were able)? I am pretty new to it all and have a batch that works the other way: both types of bentonites, seems to pass the squeeze test, but doesn't have good strength in the flask to the point of seeming dry while molding. Maybe some of the folks with more experience can lend us their wisdom.
Honestly I think I'm going to buy a bag of petrobond. I just sold some mg parts and there's money sitting in PayPal. I'll leave the experimenting for another time.
LOL that's basically what I did...until I started messing with K-Bond. The P-Bond will take away a variable while you get the hang of other parts of the process.
I got bored waiting for the petrobond to get here so I figured I'd give the greensand another shot now that some of the water has evaporated. I still have steam coming out of the mold which ruined the piece. I'll be interested to see how the petrobond works out.
Thanks for the pics. Yeah, you are going to want things to turn out better than that. Open mold is harder than closed mold for me, the metal balls up and you're not really gating it in where you want it to be/flow. The Petrobond will be a morale booster. I still want to figure out green sand long term.
God I hope it gets better! I only did an open mold because I realized I didn't have enough sand to fill both halves of the flask. I ordered 50lbs of petrobond so I should be set.
I can see your version of green sand did not work well. But in fairness to green sand, if it is mixed up with standard ingredients to a standard formula like those found in the US Navy Foundry Handbook, it works very well for aluminum. I have cast a fair number of aluminum pieces in green sand with results that were very nearly identical to petro. Here is a link to thead that was the "ultimate" comparative test. The cope was petro and the drag was green. The difference in the finish is small. http://forums.thehomefoundry.org/index.php?threads/petrobond-green-sand-hybrid-mold.1662/ Denis
I got my petrobond today and comparing it to what I made I think my sand was way too coarse. That's okay though, I called this thread scheduled disaster because I knew that the first few attempts at casting would probably be a mess.
Nothing, really, just a test to get the hang of it. I needed to make a pattern and there was an MG knockoff laying next to the band saw so I made it look kinda like that. I'll be making some real stuff now, though.
