dangerousamateur Posted February 20, 2017 Posted February 20, 2017 Please check this out: 100Kg for 50 10mm stars? That would be 0,1216752 sqare inches per star, for 49 stars about 6 Square inch. 33PSI. Aint that a little low? How much pressure do you really need to get charcoal stars that can be broken hard in shells?
OldMarine Posted February 20, 2017 Posted February 20, 2017 I've seen guys using those gang pumps that only use hand pressure to consolidate the comp but most I've read recommends at least 800 psi on the comp. I guess a lot depends on the binder and moisture content.
lloyd Posted February 20, 2017 Posted February 20, 2017 Well... yeah. That's low for "pressed" stars, which I like to see pressed at about 1500psi. However, if they're wet enough, they can be 'formed' by such a light pressure, and just like cut stars, they'll eventually harden. LLoyd
dangerousamateur Posted February 21, 2017 Author Posted February 21, 2017 Thats what i thought. I wonder how this guy got his 100kg idea... Handpumped stars have a lot of disadvantages, especially when you have to make glitters too moist... So without a monster press these plates are not very worthwhile. Thank you.
lloyd Posted February 21, 2017 Posted February 21, 2017 No... that's not what I said. I said that _I_ prefer to press dry(er), and use more pressure. I've done glitters wet enough to cut (which is about the same wetness needed for that light pressure), and they worked fine. I don't know where this 'old wives tale' about getting glitters wet comes from. Perhaps some of them decay, but mine never did. LLoyd
Mumbles Posted February 21, 2017 Posted February 21, 2017 It wouldn't really take a monster press either. A press or frame with a 6 ton bottle jack would be plenty to get it up to pressure for a star plate.
lloyd Posted February 21, 2017 Posted February 21, 2017 Heh! Yeah. One of my old powder-pressing rigs for making pressed-and-corned BP would work fine with that small of a mold. Heck! I just threw one of those out as steel scrap! (cleaning up and making room for a new project).http://www.pyrobin.com/files/press.gif Lloyd
OldMarine Posted February 21, 2017 Posted February 21, 2017 I've got a 6 ton hydraulic press from Caleb and it will accommodate any of his 6 inch square plates. Dang Lloyd! Don't be scrapping presses! I'll make a road trip for tools.
lloyd Posted February 21, 2017 Posted February 21, 2017 Ok... if I run across any more stuff like that, I'll save it for you Patrick! It was in a flood in Mobile, AL... salt water. It'd have taken quite a lot of work to restore it. Lloyd
Arthur Posted February 21, 2017 Posted February 21, 2017 Dry comps need a lot of pressure to compact to solids -but they do. Wet or damp compounds with binder will adhere as stars with much less pressure, but then they need to dry! Whether you use the china hard dry pressed stars or wet pressed stars that are often hard but porous is just one of your design decisions.
lloyd Posted February 21, 2017 Posted February 21, 2017 (edited) Arthur,I typically use 3%-5% moisture in my BP-based pressed stars. I press to somewhere between 1500psi and 2200psi on the composition. At that moisture and pressure, they dry ROCK HARD (without significant porosity) overnight - 15 hours, or so - in a dehumidified but not otherwise heated - drying closet. There is some heat added by the dehumidifier, the full cycle of which I direct into the enclosure through 'baffled' ducting; but it seldom gets over 100F. Lloyd Edited February 21, 2017 by lloyd
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