There is dried grass mixed in with the sand I swept up from the floor. I was hoping to screen that stuff out but the grass makes its way through the screen. Is there a way to get it out or will I have to accept an ongoing loss of petrobond?
If you don't want to clean the whole heap at the same time, riddle your facing sand with a very fine screen and then use the stuff with bits of grass as backing sand. It'll eventually burn out. I'd get as much of it out as you can beforehand though. I have a tarp that I put down before molding so I don't get floor dirt, etc mixed in the sand. I suspect if you're just sweeping it off the concrete floor in a common work area you're getting more than just grass in there.. Plus I'm not a big fan of having petrobond residue getting on my shoes and tracking it around every time I walk through my barn. Aside from actual oil it's probably the nastiest and hard to clean thing that gets on the bottom of my feet, truck floor, mud room mats, etc, plus it stinks. So prepare your area some and the problem should go away. I've also found that mice and chipmunks aren't bothered by petrobond because I've had to sift safflower and other hoarded bird seeds out of my sand when it was left uncovered. Pete
Just to clarify, the bulk of my sand is clean and stays clean. What I'm referring to is the sand I spill on the floor when molding and mulling and transferring to storage buckets. I've had 5 casting sessions using the new petro-bond and now I have a 1/4 bucket of contaminated sand. My options are to painstackingly sift a small amount after each clean-up or find a way to clean a bucket at a time.
Maybe use a finer screen to sift out the junk that is making it through the one you've tried using? You could try to avoid dropping sand on the floor in the first place by building a molding bench; that way the sand that falls out of the flask when you're ramming up molds just lands back in the built in bin underneath the flask... I used to keep my sand in 5-gallon plastic buckets and I'd have to move my drill press and belt/disc sander, etc., out of the way to lay out a tarp on my regular workbench to catch the sand that falls out of the flask during molding before I built my molding bench, which worked somewhat but I still lost a lot more sand with each mold than the tiny amount that presumably escapes now. My shed has a dirt and gravel floor, so there's really no retrieving sand that falls down there when I'm making molds. It would be very difficult to convince me to go back to working out of those buckets... I copied the basic idea behind Cae2100 AKA Chirpy's Tinkerings' molding bench - ie. the bin is just half of a plastic 55 gallon barrel bolted to the inside of a 2X4 frame I built around and under it. A hinged plywood lid with a blue Styrofoam gasket glued to the underside keeps out MOST of the spiders and earwigs, but it doesn't seal in the moisture quite as well as I'd hoped. I get very few foreign objects in my sand with this setup. Few enough that it is fairly easy to just pick it out when I see it. Some short plywood walls on the sides and back keep sand from flying out of the bench when I'm mixing water into my sand with a kitchen mixer beater and drill or brushing/blowing loose grains off of molds. The whole build only cost me $10 or $15 (can't remember which, but that was for the used plastic barrel, which I still have half of) because all the wood was reclaimed from an old homemade bed frame I'd stored in my other shed for 14 years until my friend finally told me he was never coming back to retrieve it.
I always lay out a clean tarp and work over that. I park my muller and buckets on the tarp. Any molding sand that makes it to the garage floor gets discarded. I lose a very small amount of sand each session. Better than finding a chip of wood or gravel at that critical feature of the mold! R
Dang, lost another handful of sand onto the dirty floor. Clearly, I need to take a real hard look at my casting procedure and make sure the floor is clean before I drop sand. I guess I better get serious about sifting contaminated sand as I go.
