See notes for substitutions, database does not have the items I needed.
Eugene Yurek Posted 9/22/2009 1:34 PM (#84801 – in reply to #84799) Subject: Re: Tube closing powder The swelling type is the sodium form (western bentonite). Thats the stuff the well drilling/remediation companies use that they buy in 50# sacks of pellets and they did tell me it was cheap. Interestingly enough, most scooping kitty litters are sodium bentonite because they swell and stick together but they add other things in there like sodium bicarb, fragrance and the like. I agree with Lee, bentonite on its own is not going to get hard enough to seal a tube well in the presence of burning flash for long enough that the thing won’t most likely jet. It has to be something else. Maybe swelling bentonite mixed with a little portland cement or maybe even mixed with some plaster of paris or something similar. Whatever it is the Chinese use, its a pretty good bet its either something they just send a worker outside with a wheel barrow and shovel to get (hehe) or its a manufacturing byproduct of some other industry. And talking about clay for rocket nozzles, bentonite is about the worst thing you could ever use. I still don’t know where this practice got adopted. You want to make some really great nozzle clay, get a bag of hawthorne bond fire clay and some fine grog around 48 mesh and a finer aggregate around 100 mesh (I use mullite, which is considered a refractory and is used as such in kiln linings). Mix them up as follows: 61% clay 16% fine grog 15% mullite which doesn’t add up to 100% because you have to bake the crap out of the above mixture at about 250F for an hour to drive out all the water (ALL clay absorbs water from the air) and then you mix in 8% candle wax and keep mixing till it all evenly looks “wet” and let cool, stirring several times so it doesn’t clump. Now press a nozzle. It will clink like bone china and its damn near 100% waterproof. It gets so hard don’t make a mistake because you won’t be drilling this stuff out and instead tossing the tube. Gene