Here's a trick I got from So. Addison on the AA forum. Of course it's always best to use the right product for the job if you can get it, but I think this is a good solution for people who might have to be making do with what materials they can find locally. I've read about other easy to find sources of sodium silicate like concrete sealer and radiator patching fluid, and found them either unavailable where I live in Canada or else I've just had bad luck getting them to work. It if you can find that stuff and get it to work, please let us know here about those experiences - this is just one way that did work for me: Wood stove gasket cement! Cures with CO2 or just a few minutes in the toaster oven. Of course there are molasses cores and linseed oil cores and probably a whole bunch of other kinds of non sodium silicate bound cores as well... But I have not tried those recipes. Let's hear about you guys' experinces wih different binders making cores for sand casting, whether you've used professional ingredients or hardware store hacks like this or whatever. Include recipes if possible! Jeff edit - got a pic of the core hole in the casting I used one of these cores for; video of the molding and casting, core placement, etc., of this aluminum bronze casting will be posted once editing is complete.
I gave up using SS years ago because it does not breakdown so I now use a epoxy fibreglass resin. SS cores needed 4-5 % , epoxy cores need only 1-1.5% and breakdown is 100% with cast iron. As an aside microwave ovens will make SS go hard.
From old foundry man.... Incidentally tell “Ironsides” that if he puts ½% glucose powder in the sand before adding the sodium silicate the core will wash out after casting quite easily, hot water sort of helps but is not really necessary and a hose does wonders.
Half-percents of this and that... Starting to sound a bit less "Quick 'n Dirty", LoL... J/k, actual specific recipes are good to have, this is all great info! I've also read about using cereal additives to improve collapsibility in cores, but I can't remember how much or if it was wheat flour or corn flour that is called for there... Might have been in the US Navy Foundry Manual or Ammen's sandcasting handbook... Might be something mentioned in one of Sandrammer's videos too IIRC. If I can remember to check later, I'll try and find some numbers. But that isn't something I have ever tried using before, personally. Jeff
the Navy Foundry Manuel gives 5 recipes for core sand . you will have to read alot of the book and do some translation, core oil means Linseed oil. cereal is dextrine or corn starch... have fun with the fact that the numbers dont add up V/r HT1
I did buy some SS with molasses, the salesman said that it would breakdown a lot more. The problem with it is that there was a lot of blowholes where the core was and I never had that problem before. Epoxy resins are so much easier to get than SS in Australia so I will stick with that.
I found one thing that really helps break down sodium silicate (SS) cores is to keep the percentage as low as possible, say 3% max. And the key to making a core rigid and durable at 3% is to NOT over-gas it with CO2. Gas it 5 seconds max with CO2. And don't ever put your core in a bag full of CO2; that is the quickest way to ruin a good core that I have found when using a 3% mix. It seems counter intuitive that less CO2 and less SS produces a much harder and more durable core, and also one that breaks down much easier with water, but I have found that to be true after using SS for several years. I have cores that have been sitting on the open workbench for at least a year, and they are fully usable with no sign of deterioration (at 3% and 5 second gassing).
Hey Pat, good to see you back among us posting again, it's been a while. Are you still making molds out of that catalyzed binder sand stuff? Sounds like you've been playing around with ss, is what makes me ask. That and just general curiosity about what you've been up to. 3% is pretty darn close to 4%, which I have seen recommended elsewhere, so yeah I bet that works great. Good tip about not over-gassing! I've been just baking mine on low heat for 10 or 15 minutes (for small cores like in the video, which is all I've tried making so far) instead of using CO2. I'm not sure I have precise enough instruments to weight it out that precisely, but I've had some luck adding just enough of the gasket glue to coat all the sand I'm mixing up. More of an eyeballing it approach with easy to find materials, hence the "quick 'n dirty" in the title. I might have used a little more than needed in the video above, but they hardened fine, just a matter of whether I'll be able to break them out later! I am all for clean and precise when it's not a huge PitA or makes a really big difference, and I always admired how you've stuck to and documented that sort of scientific approach and worked to get repeatable results, but I also wanted to show in the video that sometimes we can be overthinking these things. Time will tell if my cored casting comes out any good... I'm hoping to pour it this weekend. Gonna have the place to myself for a day or two, so the only thing that can stop me is myself! Jeff
Jeff- Good to see you and the other guys here. David was gracious enough to let me in here, and I appreciate that. For my part I will try to make a better casting community. I got busy with work this year, and especially recently, so nothing major to report; just the low-mass furnace built, and the muilti-flow burner control (which I will post more on here later). Getting good with iron pours is my central focus right now; I have seen several others do it, and I am ready for some repeatable success in that area. I watched several of your videos. Good stuff. I was using resin-binder, but the fumes are more noxious than I want in my shop, and I wanted a binder that I could use in the shop without a respirator (I do wear a dust mask). The sodium silicate works well for both cores and molds, and I use it for both. I am hoping I can start recycling the SS sand with the 3%. It seems like it will break down pretty easily with water, although I will have to bake it dry. And I am still working on publishing an article on the engine in my avatar; it going to the publisher as we speak.
Cool! Well, as mentioned, its good to have you back and see everyone getting along. Looking forward to seeing your projects progress. Thanks for watching, I'm not chasing views or monetizing or anything, but I have been putting a little more time and effort into making better videos ever since a bunch of us got screwed over by photobucket and I needed a new way to share pictures (they're the moving type a little more often now, is the main difference). So far it has been fun and has actually probably helped me more than it has anyone else - I've spotted myself doing some weird and useless things out of habit that I had no idea I was doing for one thing. There's one where you see me repeatedly dusting my mold then immediately blowing all the parting back off, several times in a row, for no apparent reason, LOL! Also discovered I mumble too much, and that when I'm not mumbling completely unintelligibly, my voice apparently sounds like I'm half drunk or stoned all the time. I had no idea! Honest, it's not ALL the time! Jeff edit - PS. pic of cored casting added to OP
