Mike, I value your observations, and those of others. Please continue with any other thoughts. Regarding your comments, following, I've inserted my observations in CAPS:
Mike D. said: G'morning Reid, > ... Tests indicate the purifiers remove 99% of all partcles down to > 1.0 micron, and I'd think this would happen near the surface. Which raises the question of whether it is at the surface that you want the most antimicrobial activity? I'M BEGINNING TO UNDERSTAND THAT THE DISINFECTION HAPPENS AT THE SURFACE, BUT I THINK IT TAKES SOME MINUTES FOR THE PATHOGENS TO DIE (SOME SAY 'BECOME INACTIVATED'). OTHERWISE I ALSO LIKE THE IDEA OF OVER KILL, SILVER THROUGHOUT THE MEDIUM. > I also want to explore the possibility of firing upto about 600C, at > which temperature the carbon should burn off. But I don't know what > this may do to the silver bond. And because of the higher > temperatures at which the pottery is fired, upto 1050C, the silver in > whatever form can only be applied after firing. The melting point of silver is 961, boiling point 2212... Vapor pressure of molten silver at 1050 C, if I calculate it right, is about 15 millitorr or 2x10e-5 atm. Given a fine-pored matrix would the silver, at most, be somewhat depleted at the surface, but still present in the bulk of the ceramic? I UNDERSTAND THAT SILVER NITRATE WILL DECOMPOSE AT ABOUT 444C. I'M TOLD SILVER IS VERY ACTIVE WITH MOST CERAMICS, BUT IT'S A LITTLE CONFUSING THAT THE CRC HANDBOOK SAYS THAT SILVER OXIDE WILL GO TO SILVER METAL AS LOW AS 230C. WHO AMONG US KNOWS WHAT THE HECK IS HAPPENING WITH THE SILVER AT 600? THAT'S THE TEMP WHERE CARBON BURNS OFF. SHORT OF A LOT OF EXPERIMENTATION SOME KIND OF HEADS UP WOULD BE REALLY HELPFUL. ANYHOW, WHATEVER WE DO COME UP WITH FOR SILVER, THE POTTERY MEDIUM IS PROVING TO BE VERY APPROPRIATE. Would it be worth a try to mix the dry clay with CS or a silver nitrate solution instead of water, and testing the resulting material for germicidal activity? MIXING WITH THE CLAY, AND NOT SATURATING WITH THE FIRED CERAMIC MEDIUM, MAY CARRY A WHOLE DIFFERENT SET OF PROBLEMS. FOR ONE THING THERE WILL HAVE BEEN NO BONDING BETWEEN ADJACENT CLAY PARTICLES, WHICH HAPPENS AT UPPER TEMPERATURES. CERAMISTS CALL THIS PHENOMENON 'SPOT WELDING' FOR WANT OF A BETTER TERM. THE PERMEABLE MEDIUM FOR A PILE OF CLAY PARTICLES WOULD BE QUITE DIFFERENT. As for firing to 600C to burn off the carbon, what are you concerned about? The form the silver might take? Your hope is to be left with silver metal, right? Does silver form oxides at those temperatures? I'M CONCERNED THAT PROSPECTIVES USERS OF THE PURIFIERS MAY NOT GO FOR A BLACK ONE. WHAT'S USUALLY IN THE MARKET IS SOMEWHAT WHITE, AND IT MAY EVEN BE A BIT OF A LEAP FOR PEOPLE TO ACCEPT OUR RED PURIFIERS. ALSO, SILVER METAL SHOULD HAVE THE ADVANTAGE THAT IT'S BONDED TO THE CERAMIC AND NOT JUST STUCK THERE, AS SILVER OXIDE IS. Interesting work, Reid. Be well, Mike D. -- The silver-list is a moderated forum for discussion of colloidal silver. Instructions for unsubscribing may be found at: http://silverlist.org To post, address your message to: [email protected] Silver-list archive: http://escribe.com/health/thesilverlist/index.html List maintainer: Mike Devour <[email protected]>
